Planetary boundaries
Encyclopedia
Planetary boundaries is the central concept in an Earth system framework proposed by a group of Earth system
and environmental scientists
led by Johan Rockström
from the Stockholm Resilience Centre
and Will Steffen
from the Australian National University
. In 2009, the group proposed a framework for planetary boundaries which can potentially identify a safe operating space for government and management agencies as a precondition for sustainable development
. The scientists identified nine Earth system processes which have boundaries that, to the extent that they are not crossed, mark the safe zone for the planet. However, because of human activities some of these dangerous boundaries have already been crossed, while others are in imminent danger of being crossed.
Rockström and Steffen collaborated with 26 leading academics, including Nobel
laureate Paul Crutzen, Goddard Institute for Space Studies
climate scientist James Hansen
and the German Chancellor's chief climate adviser Hans Joachim Schellnhuber
. The group identified nine "planetary life support systems" essential for human survival, and attempted to quantify just how far seven of these systems have been pushed already. They then estimated how much further we can go before our own survival is threatened; beyond these boundaries there is a risk of "irreversible and abrupt environmental change" which could make Earth less habitable
. Estimates indicate that three of these boundaries—climate change
, biodiversity loss, and the biogeochemical flow boundary—appears to have been crossed. The boundaries are "rough, first estimates only, surrounded by large uncertainties and knowledge gaps" that interact in ways that are complex and not well understood. Boundaries can help identify where there is room and define a "safe space for human development", which is an improvement on approaches which aim at just minimizing human impacts on the planet.
The group published their full findings in a 2009 report and presented it to the General Assembly of the Club of Rome
in Amsterdam. An edited summary of the report was subsequently published as the featured article in a special edition of Nature
. Nature also published critical commentary from leading academics they invited to comment on each of the seven planetary boundaries which had been quantified, including comments from Nobel laureate Mario J. Molina
and biologist Cristián Samper
.
The idea that our planet has limits, including the burden placed upon it by human activities, has been around for some time. In 1972, The Limits to Growth was published. It presented a model in which five variables: world population
, industrialization, pollution
, food production, and resources depletion, are examined, and considered to grow exponentially
, whereas the ability of technology to increase resources availability is only linear
. Subsequently, the report was widely dismissed, particularly by economists and businessmen, and it has often been claimed that history has proved the projections to be incorrect. In 2008, Graham Turner from the Commonwealth Scientific and Industrial Research Organisation
(CSIRO) published a paper called "A comparison of The Limits to Growth with thirty years of reality". Turner found that the observed historical data from 1970 to 2000 closely matches the simulated results of the "standard run" limits of growth model for almost all the outputs reported. "The comparison is well within uncertainty bounds of nearly all the data in terms of both magnitude and the trends over time." Turner also examined a number of the reports, particularly by economists, which over the years purported to discredit the limits to growth model. Turner says these reports are flawed, and reflect misunderstandings about the model. In 2010, Nørgård, Peet and Ragnarsdóttir called the book a "pioneering report", and said that it "has withstood the test of time and, indeed, has only become more relevant."
Our Common Future
was published in 1987 by United Nations' World Commission on Environment and Development
. It tried to recapture the spirit of the Stockholm Conference
. Its aim was to interlock the concepts of development and environment for future political discussions. It introduced the famous definition for sustainable development
:
Of a different kind is the approach made by James Lovelock
. In the 1970s he and microbiologist
Lynn Margulis
presented the Gaia theory or hypothesis
, that states that all organisms and their inorganic surroundings on Earth are integrated into a single self-regulating system. The system has the ability to react to perturbations or deviations, much like a living organism adjusts its regulation mechanisms to accommodate environmental changes such as temperature (homeostasis
). Nevertheless, this capacity has limits, and in the same way that, for instance, when a living organism is subjected to a temperature that is lower that its living range, will probably perish, because its regulating mechanism can not make the necessary adjustments to withstand it, similarly the earth may not be able to react in front of too big deviations of critical parameters. In his book The Revenge of Gaia
, he affirms that the destruction of rainforests and biodiversity, compounded with the increase of greenhouse gases made by humans, is producing global warming
.
began about 10,000 years ago. It is the current interglacial
period, and it has proven to be a relatively stable environment for the Earth. There have been natural environmental fluctuations during the Holocene, but the key atmospheric and biogeochemical parameters have been relatively stable. This stability and resilience
has allowed agriculture to develop and complex societies to thrive. According to Rockström et al., we "have now become so dependent on those investments for our way of life, and how we have organized society, technologies, and economies around them, that we must take the range within which Earth System processes varied in the Holocene as a scientific reference point for a desirable planetary state."
Since the industrial revolution
, according to Paul Crutzen
, Will Steffen and others, the planet has entered a new epoch, the Anthropocene
. In the Anthropocene, humans have become the main agents of change to the Earth system. There have been well publicized scientific warnings about risks in the areas of climate change and stratospheric ozone. However, other biophysical processes are also important. For example, since the advent of the Anthropocene, the rate at which species are being extinguished has increased over 100 times, and humans are now the driving force altering global river flows as well as water vapor flows from the land surface. Continuing pressure on the Earth's biophysical systems from human activities raises concerns that further pressure could be destabilizing, and precipitate sudden or irreversible changes to the environment. It is difficult to address the issue, because the predominant paradigms of social and economic development are largely indifferent to the looming possibilities of large scale environmental disasters triggered by humans.
The threshold, or tipping point
, is the value at which a very small increment for the control variable (like CO2) produces a very big change, even catastrophic, in the response variable (global warming).
The threshold points are difficult to locate, because the Earth System is very complex. Instead of defining the threshold value, the study establishes a range, and the threshold is supposed to lie inside it. The lower end of that range is defined as the boundary. Therefore it defines a safe space, in the sense that as long as we are below the boundary, we are below the threshold value. If the boundary is crossed, we enter into a danger zone.
The proposed framework of planetary boundaries lays the groundwork for shifting approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externaliti
es, toward the estimation of the safe space for human development
. Planetary boundaries define, as it were, the boundaries of the “planetary playing field” for humanity if major human-induced environmental change on a global scale is to be avoided
Transgressing one or more planetary boundaries may be highly damaging or even catastrophic, due to the risk of crossing thresholds that trigger non-linear, abrupt environmental change
within continent
al- to planetary-scale systems. The 2009 study identified nine planetary boundaries and, drawing on current scientific understanding, the researchers proposed quantifications for seven of them. These seven are climate change (CO2
concentration in the atmosphere < 350 ppm and/or a maximum change of +1 W/m2 in radiative forcing
); ocean acidification
(mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial
levels); stratospheric
ozone (less than 5% reduction in total atmospheric O3
from a pre-industrial level of 290 Dobson Unit
s); biogeochemical
nitrogen (N) cycle
(limit industrial and agricultural fixation of N2 to 35 Tg N/yr) and phosphorus (P) cycle
(annual P inflow to oceans not to exceed 10 times the natural background weathering
of P); global freshwater use (< 4000 km3/yr of consumptive use of runoff resources); land system change (< 15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of < 10 extinctions per million species). The two additional planetary boundaries for which the group had not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading
.
Christopher Field
, director of the Carnegie Institution's Department of Global Ecology, is impressed: "This kind of work is critically important. Overall, this is an impressive attempt to define a safety zone." But the conservation biologist Stuart Pimm
is not impressed: "I don’t think this is in any way a useful way of thinking about things… The notion of a single boundary is just devoid of serious content. In what way is an extinction rate 10 times the background rate acceptable?" and the environmental policy analyst Bill Clark
thinks: "Tipping points in the earth system are dense, unpredictable... and unlikely to be avoidable through early warning indicators. It follows that... 'safe operating spaces' and 'planetary boundaries' are thus highly suspect and potentially the new 'opiates'."
The biogeochemist William Schlesinger
queries whether thresholds are a good idea for pollutions at all. He thinks waiting until we near some suggested limit will just permit us to continue to a point where it is too late. "Management based on thresholds, although attractive in its simplicity, allows pernicious, slow and diffuse degradation to persist nearly indefinitely."
The hydrologist David Molden thinks planetary boundaries are a welcome new approach in the 'limits to growth' debate. "As a scientific organizing principle, the concept has many strengths [...] the numbers are important because they provide targets for policymakers, giving a clear indication of the magnitude and direction of change. They also provide benchmarks and direction for science. As we improve our understanding of Earth processes and complex inter-relationships, these benchmarks can and will be updated [...] we now have a tool we can use to help us think more deeply—and urgently—about planetary limits and the critical actions we have to take."
The ocean chemist Peter Brewer queries whether it is "truly useful to create a list of environmental limits without serious plans for how they may be achieved [...] they may become just another stick to beat citizens with. Disruption of the global nitrogen cycle is one clear example: it is likely that a large fraction of people on Earth would not be alive today without the artificial production of fertilizer. How can such ethical and economic issues be matched with a simple call to set limits? [...] food is not optional."
The environment advisor Steve Bass says the "description of planetary boundaries is a sound idea. We need to know how to live within the unusually stable conditions of our present Holocene period and not do anything that causes irreversible environmental change […] Their paper has profound implications for future governance systems, offering some of the 'wiring' needed to link governance of national and global economies with governance of the environment and natural resources. The planetary boundaries concept should enable policymakers to understand more clearly that, like human rights and representative government, environmental change knows no borders."
The climate change policy advisor Adele Morris thinks that price-based policies are also needed to avoid political and economic thresholds. "Staying within a 'safe operating space' will require staying within all the relevant boundaries, including the electorate’s willingness to pay."
In 2011, at their second meeting, the High-level Panel on Global Sustainability of the United Nations
incorporated the concept of planetary boundaries into their framework, stating that their goal was: "To eradicate poverty and reduce inequality, make growth inclusive, and production and consumption more sustainable while combating climate change and respecting the range of other planetary boundaries."
Elsewhere in their proceedings, panel members have expressed reservations about the political effectiveness of using the concept of "planetary boundaries" : "Planetary boundaries are still an evolving concept that should be used with caution […] The planetary boundaries question can be divisive as it can be perceived as a tool of the “North” to tell the “South” not to follow the resource intensive and environmentally destructive development pathway that rich countries took themselves… This language is unacceptable to most of the developing countries as they fear that an emphasis on boundaries would place unacceptable brakes on poor countries."
However, the concept is routinely used in the proceedings of the United Nations, and in the UN Daily News. For example, the UNEP Executive Director Achim Steiner
states that the challenge of agriculture is to "feed a growing global population without pushing humanity's footprint
beyond planetary boundaries." The United Nations Environment Programme
(UNEP) Yearbook 2010 also repeated Rockström's message, conceptually linking it with ecosystem management
and environmental governance indicators
.
The planetary boundaries concept is also used in proceedings by the European Commission
, and was referred to in the European Environment Agency
synthesis report The European environment – state and outlook 2010.
is a measure of the difference between the incoming radiation energy
and the outgoing radiation energy acting across the boundary of the earth. Positive radiative forcing results in warming. From the start of the industrial revolution in 1750 to 2005, the increase in atmospheric carbon dioxide has led to a positive radiative forcing, averaging about 1.66 W
/m².
The climate scientist Myles Allen
thinks setting "a limit on long-term atmospheric carbon dioxide concentrations merely distracts from the much more immediate challenge of limiting warming to 2 °C." He says the concentration of carbon dioxide is not a control variable we can "meaningfully claim to control", and he questions whether keeping carbon dioxide levels below 350 ppm will avoid more than 2 °C of warming.
Adele Morris, policy director, Climate and Energy Economics Project, Brookings Institution
, makes a criticism from the economical-political point of view. She puts emphasis in choosing policies that minimize costs and preserve consensus. She favors a system of green-house gas emissions tax
, and emissions trading
, as ways to prevent global warming. She thinks that too-ambitious objectives, like the boundary limit on CO2, may discourage such actions.
, a " boundary that expresses the probability of families of species disappearing over time would better reflect our potential impacts on the future of life on Earth."
The conservation ecologist Gretchen Daily claims that "it is time to confront the hard truth that traditional approaches to conservation, taken alone, are doomed to fail. Nature reserves are too small, too few, too isolated and too subject to change to support more than a tiny fraction of Earth’s biodiversity. The challenge is to make conservation attractive—from economic and cultural perspectives. We cannot go on treating nature like an all-you-can-eat buffet. We depend on nature for food security, clean water, climate stability, seafood, timber, and other biological and physical services. To maintain these benefits, we need not just remote reserves but places everywhere—more like 'ecosystem service stations.' A few pioneers are integrating conservation and human development. The Costa Rican government is paying landowners for ecosystem services from tropical forests, including carbon offsets, hydropower production, biodiversity conservation and scenic beauty. China is investing $100 billion in “ecocompensation,” including innovative policy and finance mechanisms that reward conservation and restoration. The country is also creating “ecosystem function conservation areas” that make up 18 percent of its land area. Colombia
and South Africa
have made dramatic policy changes, too. Three advances would help the rest of the world scale such models of success. One: new science and tools to value and account for natural capital, in biophysical, economic and other terms [...] Two: compelling demonstrations of such tools in resource policy. Three: cooperation among governments, development organizations, corporations and communities to help nations build more durable economies while also maintaining critical ecosystem services."
Since the industrial revolution, the Earth's nitrogen cycle
has been disturbed even more than the carbon cycle. "Human activities now convert more nitrogen from the atmosphere into reactive forms than all of the Earth´s terrestrial processes combined. Much of this new reactive nitrogen pollutes waterways and coastal zones, is emitted back to the atmosphere in changed forms, or accumulates in the terrestrial biosphere." Only a small part of the fertilizers applied in agriculture is used by plants. Most of the nitrogen and phosphorus ends up in rivers, lakes and the sea, where excess amounts stress aquatic ecosystems. For example, fertilizer which discharges from rivers into the Gulf of Mexico has damaged shrimp fisheries
because of hypoxia
.
The biogeochemist William Schlesinger
thinks waiting until we near some suggested limit for nitrogen deposition and other pollutions will just permit us to continue to a point where it is too late. He says the boundary suggested for phosphorus is not sustainable, and would exhaust the known phosphorus reserves in less than 200 years.
With regard to nitrogen, the biogeochemist and ecosystem scientist Robert Howarth says: "Human activity has greatly altered the flow of nitrogen across the globe. The single largest contributor is fertilizer use. But the burning of fossil fuels actually dominates the problem in some regions, such as the northeastern U.S. The solution in that case is to conserve energy and use it more efficiently. Hybrid vehicles are another excellent fix; their nitrogen emissions are significantly less than traditional vehicles because their engines turn off while the vehicle is stopped. (Emissions from conventional vehicles actually rise when the engine is idling.) Nitrogen emissions from U.S. power plants could be greatly reduced, too, if plants that predate the Clean Air Act and its amendments were required to comply; these plants pollute far out of proportion to the amount of electricity they produce. In agriculture, many farmers could use less fertilizer, and the reductions in crop yields would be small or nonexistent. Runoff from corn fields is particularly avoidable because corn’s roots penetrate only the top few inches of soil and assimilate nutrients for only two months of the year. In addition, nitrogen losses can be reduced by 30 percent or more if farmers plant winter cover crops, such as rye or wheat, which can help the soil hold nitrogen. These crops also increase carbon sequestration in soils, mitigating climate change. Better yet is to grow perennial plants such as grasses rather than corn; nitrogen losses are many times lower. Nitrogen pollution from concentrated animal feeding operations (CAFOs) is a huge problem. As recently as the 1970s, most animals were fed local crops, and the animals’ wastes were returned to the fields as fertilizer. Today most U.S. animals are fed crops grown hundreds of miles away, making it “uneconomical” to return the manure. The solution? Require CAFO owners to treat their wastes, just as municipalities must do with human wastes. Further, if we ate less meat, less waste would be generated and less synthetic fertilizer would be needed to grow animal feed. Eating meat from animals that are range-fed on perennial grasses would be ideal. The explosive growth in the production of ethanol as a biofuel is greatly aggravating nitrogen pollution. Several studies have suggested that if mandated U.S. ethanol targets are met, the amount of nitrogen flowing down the Mississippi River and fueling the Gulf of Mexico dead zone may increase by 30 to 40 percent. The best alternative would be to forgo the production of ethanol from corn. If the country wants to rely on biofuels, it should instead grow grasses and trees and burn these to co-generate heat and electricity; nitrogen pollution and greenhouse gas emissions would be much lower."
The ocean engineer David Vaccari says that the "most sustainable flow of phosphorus through the environment would be the natural flux: seven million metric tons per year (Mt/yr). To hit that mark yet satisfy our usage of 22 Mt/yr, we would have to recycle or reuse 72 percent of our phosphorus […] The flow could be reduced with existing technologies… [lowering] the loss to waterways from 22 to 8.25 Mt/yr, not very much above the natural flux."
. This acidity inhibits the ability of corals, shellfish and plankton to build shells and skeletons. Knock-on effects
could have serious consequences for fish stock
s. This boundary is clearly interconnected with the climate change boundaries, since the concentration of carbon dioxide in the atmosphere is also the underlying control variable for the ocean acidification boundary.
The ocean chemist Peter Brewer thinks "ocean acidification has impacts other than simple changes in pH, and these may need boundaries too."
The marine chemist Scott Doney thinks "the main tactics are raising energy efficiency, switching to renewable and nuclear power, protecting forests and exploring carbon sequestration technologies. Regionally, nutrient runoff to coastal waters not only creates dead zones but also amplifies acidification. The excess nutrients cause more phytoplankton to grow, and as they die the added CO2 from their decay acidifies the water. We have to be smarter about how we fertilize fields and lawns and treat livestock manure and sewage […] Locally, acidic water could be buffered with limestone or chemical bases produced electrochemically from seawater and rocks. More practical may be protecting specific shellfish beds and aquaculture fisheries. Larval mollusks such as clams and oysters appear to be more susceptible to acidification than adults, and recycling old clamshells into the mud may help buffer pH and provide better substrate for larval attachment. The drop in ocean pH is expected to accelerate in coming decades, so marine ecosystems will have to adapt. We can enhance their chances for success by reducing other insults such as water pollution and overfishing, making them better able to withstand some acidification while we transition away from a fossil-fuel energy economy."
s, impacting freshwater, carbon and other cycles, and reducing biodiversity.
The environment advisor Steve Bass says research tells us that "the sustainability of land use depends less on percentages and more on other factors. For example, the environmental impact of 15 per cent coverage by intensively farmed cropland in large blocks will be significantly different from that of 15 per cent of land farmed in more sustainable ways, integrated into the landscape. The boundary of 15 per cent land-use change is, in practice, a premature policy guideline that dilutes the authors' overall scientific proposition. Instead, the authors might want to consider a limit on soil degradation or soil loss. This would be a more valid and useful indicator of the state of terrestrial health."
The Earth systems scientist Eric Lambin thinks that "intensive agriculture should be concentrated on land that has the best potential for high-yield crops […] We can avoid losing the best agricultural land by controlling land degradation, freshwater depletion and urban sprawl. This step will require zoning and the adoption of more efficient agricultural practices, especially in developing countries. The need for farmland can be lessened, too, by decreasing waste along the food distribution chain, encouraging slower population growth, ensuring more equitable food distribution worldwide and significantly reducing meat consumption in rich countries."
Human pressures on global freshwater
systems are having dramatic effects
. The freshwater cycle
is another boundary significantly affected by climate change. Freshwater resources, such as lake
s and aquifer
s, are usually renewable resources which naturally recharge (the term fossil water
is sometimes used to describe aquifers which don't recharge). Overexploitation
occurs if a water resource is mined or extracted at a rate that exceeds the recharge rate. Recharge usually comes from area streams, rivers and lakes. Forests enhance the recharge of aquifers in some locales, although generally forests are a major source of aquifer depletion
. Depleted aquifers can become polluted with contaminants such as nitrate
s, or permanently damaged through subsidence or through saline intrusion from the ocean. This turns much of the world's underground water and lakes into finite resources with peak usage debates similar to oil
. Though Hubbert's original analysis did not apply to renewable resources, their overexploitation can result in a Hubbert-like peak. A modified Hubbert curve
applies to any resource that can be harvested faster than it can be replaced.
The hydrologist Peter Gleick
comments: "Few rational observers deny the need for boundaries to freshwater use. More controversial is defining where those limits are or what steps to take to constrain ourselves within them. Another way to describe these boundaries is the concept of peak water
. Three different ideas are useful. 'Peak renewable' water limits are the total renewable flows in a watershed. Many of the world’s major rivers are already approaching this threshold—when evaporation and consumption surpass natural replenishment from precipitation and other sources. 'Peak nonrenewable' limits apply where human use of water far exceeds natural recharge rates, such as in fossil groundwater basins of the Great Plains, Libya, India, northern China and parts of California’s Central Valley. 'Peak ecological' water is the idea that for any hydrological system, increasing withdrawals eventually reach the point where any additional economic benefit of taking the water is outweighed by the additional ecological destruction that causes. Although it is difficult to quantify this point accurately, we have clearly passed the point of peak ecological water in many basins around the world where huge damage has occurred […] The good news is that the potential for savings, without hurting human health or economic productivity, is vast. Improvements in water-use efficiency are possible in every sector. More food can be grown with less water (and less water contamination) by shifting from conventional flood irrigation to drip and precision sprinklers, along with more accurately monitoring and managing soil moisture. Conventional power plants can change from water cooling to dry cooling, and more energy can be generated by sources that use extremely little water, such as photovoltaics and wind."
The hydrologist David Molden says "a global limit on water consumption is necessary, but the suggested planetary boundary of 4,000 cubic kilometres per year is too generous."
The stratospheric ozone layer
protectively filters ultraviolet radiation (UV) from the Sun
, which would otherwise damage biological systems. The actions taken after the Montreal Protocol
appeared to be keeping the planet within a safe boundary. However in 2011, according to a paper published in Nature, the boundary was unexpectedly pushed in the Arctic; "... the fraction of the Arctic vortex in March with total ozone less than 275 Dobson units (DU) is typically near zero, but reached nearly 45%".
The Nobel laureate in chemistry, Mario Molina
, says "five per cent is a reasonable limit for acceptable ozone depletion, but it doesn't represent a tipping point".
The physicist David Fahey says that as a result of the Montreal Protocol "stratospheric ozone depletion will largely reverse by 2100. The gain has relied, in part, on intermediate substitutes, notably hydrochlorofluorocarbons (HCFCs), and the growing use of compounds that cause no depletion, such as hydrofluorocarbons (HFCs). Ongoing success depends on several steps:
"The two panels will also have to evaluate climate change and ozone recovery together. Climate change affects ozone abundance by altering the chemical composition and dynamics of the stratosphere, and compounds such as HCFCs and HFCs are greenhouse gases. For example, the large projected demand for HFCs could significantly contribute to climate change."
particles in the atmosphere impact the health of humans and influence monsoon
and global atmospheric circulation
systems. Some aerosols produce clouds which cool the Earth by reflecting sunlight back to space, while others, like soot, produce thin clouds in the upper stratosphere which behave like a greenhouse, warming the Earth. On balance, anthropogenic aerosols probably produce a net negative radiative forcing
(cooling influence). Worldwide each year, aerosol particles result in about 800,000 premature deaths. Aerosol loading is sufficiently important to be included among the planetary boundaries, but it is not yet clear whether an appropriate safe threshold measure can be identified.
s, have potentially irreversible additive
and synergic effects on biological organisms, reducing fertility and resulting in permanent genetic damage. Sublethal uptakes are drastically reducing marine bird and mammal populations. This boundary seems important, although it is hard to quantify.
A Bayesian emulator for persistent organic pollutants has been developed which can potentially be used to quantify the boundaries for chemical pollution.
For example, the land use
boundary could shift downward if the freshwater boundary is breached, causing lands to become arid and unavailable for agriculture. At a regional level, water resources may decline in Asia if deforestation
continues in the Amazon
. Such considerations suggest the need for "extreme caution in approaching or transgressing any individual planetary boundaries."
Another example has to do with coral reef
s and marine ecosystem
s. In 2009, showed that, since 1990, calcification in the reefs of the Great Barrier
that they examined decreased at a rate unprecedented over the last 400 years (14% in less than 20 years). Their evidence suggests that the increasing temperature stress and the declining ocean saturation state of aragonite
is making it difficult for reef corals to deposit calcium carbonate. explored how multiple stressors, such as increased nutrient loads and fishing pressure, move corals into less desirable ecosystem states. showed that ocean acidification will significantly change the distribution and abundance of a whole range of marine life, particularly species "that build skeletons, shells, and tests of biogenic calcium carbonate. "Increasing temperatures, surface UV radiation levels and ocean acidity all stress marine biota
, and the combination of these stresses may well cause perturbations in the abundance and diversity of marine biological systems that go well beyond the effects of a single stressor acting alone."
Earth system science
Earth system science seeks to integrate various fields of academic study to understand the Earth as a system. It considers interaction between the atmosphere, hydrosphere, lithosphere , biosphere, and heliosphere....
and environmental scientists
Environmental science
Environmental science is an interdisciplinary academic field that integrates physical and biological sciences, to the study of the environment, and the solution of environmental problems...
led by Johan Rockström
Johan Rockström
Johan Rockström is executive director of the Stockholm Environment Institute and the Stockholm Resilience Centre, and teaches natural resource management at Stockholm University...
from the Stockholm Resilience Centre
Stockholm Resilience Centre
The Stockholm Resilience Centre is an international research centre at Stockholm University that focuses on the resilience of social-ecological systems....
and Will Steffen
Will Steffen
Will Steffen, born 1947, is the executive director of the Australian National University Climate Change Institute. From 1998 to 2004, he was the executive director of the International Geosphere-Biosphere Programme, a coordinating body of national environmental change organizations based in...
from the Australian National University
Australian National University
The Australian National University is a teaching and research university located in the Australian capital, Canberra.As of 2009, the ANU employs 3,945 administrative staff who teach approximately 10,000 undergraduates, and 7,500 postgraduate students...
. In 2009, the group proposed a framework for planetary boundaries which can potentially identify a safe operating space for government and management agencies as a precondition for sustainable development
Sustainable development
Sustainable development is a pattern of resource use, that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for generations to come...
. The scientists identified nine Earth system processes which have boundaries that, to the extent that they are not crossed, mark the safe zone for the planet. However, because of human activities some of these dangerous boundaries have already been crossed, while others are in imminent danger of being crossed.
Rockström and Steffen collaborated with 26 leading academics, including Nobel
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
laureate Paul Crutzen, Goddard Institute for Space Studies
Goddard Institute for Space Studies
The NASA Goddard Institute for Space Studies , at Columbia University in New York City, is a component laboratory of NASA's Goddard Space Flight Center Earth-Sun Exploration Division and a unit of The Earth Institute at Columbia University...
climate scientist James Hansen
James Hansen
James E. Hansen heads the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland. He has held this position since 1981...
and the German Chancellor's chief climate adviser Hans Joachim Schellnhuber
Hans Joachim Schellnhuber
Hans Joachim "John" Schellnhuber is the founding Director of Potsdam Institute for Climate Impact Research and Chair of the German Advisory Council on Global Change. He is also providing advice to the President of the European Union Commission, José Manuel Barroso....
. The group identified nine "planetary life support systems" essential for human survival, and attempted to quantify just how far seven of these systems have been pushed already. They then estimated how much further we can go before our own survival is threatened; beyond these boundaries there is a risk of "irreversible and abrupt environmental change" which could make Earth less habitable
Planetary habitability
Planetary habitability is the measure of a planet's or a natural satellite's potential to sustain life. Life may develop directly on a planet or satellite or be transferred to it from another body, a theoretical process known as panspermia...
. Estimates indicate that three of these boundaries—climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
, biodiversity loss, and the biogeochemical flow boundary—appears to have been crossed. The boundaries are "rough, first estimates only, surrounded by large uncertainties and knowledge gaps" that interact in ways that are complex and not well understood. Boundaries can help identify where there is room and define a "safe space for human development", which is an improvement on approaches which aim at just minimizing human impacts on the planet.
The group published their full findings in a 2009 report and presented it to the General Assembly of the Club of Rome
Club of Rome
The Club of Rome is a global think tank that deals with a variety of international political issues. Founded in 1968 at Accademia dei Lincei in Rome, Italy, the CoR describes itself as "a group of world citizens, sharing a common concern for the future of humanity." It consists of current and...
in Amsterdam. An edited summary of the report was subsequently published as the featured article in a special edition of Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
. Nature also published critical commentary from leading academics they invited to comment on each of the seven planetary boundaries which had been quantified, including comments from Nobel laureate Mario J. Molina
Mario J. Molina
Mario José Molina-Pasquel Henríquez is a Mexican chemist and one of the most prominent precursors to the discovering of the Antarctic ozone hole. He was a co-recipient Mario José Molina-Pasquel Henríquez (born March 19, 1943 in Mexico City) is a Mexican chemist and one of the most prominent...
and biologist Cristián Samper
Cristián Samper
Cristián T. Samper Kutschbach is a Colombian-American biologist and Director of the Smithsonian Institution's National Museum of Natural History. He was acting secretary of the Smithsonian from 2007 to 2008, the first Latin American to hold the position.-Career:Samper graduated in 1987 from the...
.
The idea of planetary boundaries or limits
World population
The world population is the total number of living humans on the planet Earth. As of today, it is estimated to be billion by the United States Census Bureau...
, industrialization, pollution
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
, food production, and resources depletion, are examined, and considered to grow exponentially
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
, whereas the ability of technology to increase resources availability is only linear
Linear function
In mathematics, the term linear function can refer to either of two different but related concepts:* a first-degree polynomial function of one variable;* a map between two vector spaces that preserves vector addition and scalar multiplication....
. Subsequently, the report was widely dismissed, particularly by economists and businessmen, and it has often been claimed that history has proved the projections to be incorrect. In 2008, Graham Turner from the Commonwealth Scientific and Industrial Research Organisation
Commonwealth Scientific and Industrial Research Organisation
The Commonwealth Scientific and Industrial Research Organisation is the national government body for scientific research in Australia...
(CSIRO) published a paper called "A comparison of The Limits to Growth with thirty years of reality". Turner found that the observed historical data from 1970 to 2000 closely matches the simulated results of the "standard run" limits of growth model for almost all the outputs reported. "The comparison is well within uncertainty bounds of nearly all the data in terms of both magnitude and the trends over time." Turner also examined a number of the reports, particularly by economists, which over the years purported to discredit the limits to growth model. Turner says these reports are flawed, and reflect misunderstandings about the model. In 2010, Nørgård, Peet and Ragnarsdóttir called the book a "pioneering report", and said that it "has withstood the test of time and, indeed, has only become more relevant."
Our Common Future
Our Common Future
Our Common Future, also known as the Brundtland Report, from the United Nations World Commission on Environment and Development was published in 1987....
was published in 1987 by United Nations' World Commission on Environment and Development
Brundtland Commission
The Brundtland Commission, formally the World Commission on Environment and Development , known by the name of its Chair Gro Harlem Brundtland, was convened by the United Nations in 1983...
. It tried to recapture the spirit of the Stockholm Conference
United Nations Conference on the Human Environment
The United Nations Conference on the Human Environment was an international conference convened under United Nations auspices held in Stockholm, Sweden from June 5–16, 1972...
. Its aim was to interlock the concepts of development and environment for future political discussions. It introduced the famous definition for sustainable development
Sustainable development
Sustainable development is a pattern of resource use, that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for generations to come...
:
- "development that meets the needs of the present without compromising the ability of future generations to meet their own needs."
Of a different kind is the approach made by James Lovelock
James Lovelock
James Lovelock, CH, CBE, FRS is an independent scientist, environmentalist and futurologist who lives in Devon, England. He is best known for proposing the Gaia hypothesis, which postulates that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling...
. In the 1970s he and microbiologist
Microbiologist
A microbiologist is a scientist who works in the field of microbiology. Microbiologists study organisms called microbes. Microbes can take the form of bacteria, viruses, fungi, and protists...
Lynn Margulis
Lynn Margulis
Lynn Margulis was an American biologist and University Professor in the Department of Geosciences at the University of Massachusetts Amherst. She is best known for her theory on the origin of eukaryotic organelles, and her contributions to the endosymbiotic theory, which is now generally accepted...
presented the Gaia theory or hypothesis
Gaia hypothesis
The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet.The scientific investigation of the...
, that states that all organisms and their inorganic surroundings on Earth are integrated into a single self-regulating system. The system has the ability to react to perturbations or deviations, much like a living organism adjusts its regulation mechanisms to accommodate environmental changes such as temperature (homeostasis
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
). Nevertheless, this capacity has limits, and in the same way that, for instance, when a living organism is subjected to a temperature that is lower that its living range, will probably perish, because its regulating mechanism can not make the necessary adjustments to withstand it, similarly the earth may not be able to react in front of too big deviations of critical parameters. In his book The Revenge of Gaia
The Revenge of Gaia
The Revenge of Gaia: Why the Earth is Fighting Back – and How we Can Still Save Humanity is a book by James Lovelock.- External links :* The Revenge of Gaia * , edited extract from The Guardian, 24 March 2006...
, he affirms that the destruction of rainforests and biodiversity, compounded with the increase of greenhouse gases made by humans, is producing global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
.
From Holocene to Anthropocene
The HoloceneHolocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
began about 10,000 years ago. It is the current interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
period, and it has proven to be a relatively stable environment for the Earth. There have been natural environmental fluctuations during the Holocene, but the key atmospheric and biogeochemical parameters have been relatively stable. This stability and resilience
Resilience (ecology)
In ecology, resilience is the capacity of an ecosystem to respond to a perturbation or disturbance by resisting damage and recovering quickly. Such perturbations and disturbances can include stochastic events such as fires, flooding, windstorms, insect population explosions, and human activities...
has allowed agriculture to develop and complex societies to thrive. According to Rockström et al., we "have now become so dependent on those investments for our way of life, and how we have organized society, technologies, and economies around them, that we must take the range within which Earth System processes varied in the Holocene as a scientific reference point for a desirable planetary state."
Since the industrial revolution
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...
, according to Paul Crutzen
Paul J. Crutzen
Paul Jozef Crutzen is a Dutch Nobel prize winning atmospheric chemist.Crutzen is best known for his research on ozone depletion. He lists his main research interests as “Stratospheric and tropospheric chemistry, and their role in the biogeochemical cycles and climate”...
, Will Steffen and others, the planet has entered a new epoch, the Anthropocene
Anthropocene
The Anthropocene is a recent and informal geologic chronological term that serves to mark the evidence and extent of human activities that have had a significant global impact on the Earth's ecosystems...
. In the Anthropocene, humans have become the main agents of change to the Earth system. There have been well publicized scientific warnings about risks in the areas of climate change and stratospheric ozone. However, other biophysical processes are also important. For example, since the advent of the Anthropocene, the rate at which species are being extinguished has increased over 100 times, and humans are now the driving force altering global river flows as well as water vapor flows from the land surface. Continuing pressure on the Earth's biophysical systems from human activities raises concerns that further pressure could be destabilizing, and precipitate sudden or irreversible changes to the environment. It is difficult to address the issue, because the predominant paradigms of social and economic development are largely indifferent to the looming possibilities of large scale environmental disasters triggered by humans.
The nine boundaries
Thresholds and boundariesThe threshold, or tipping point
Tipping point
In sociology, a tipping point is the event of a previously rare phenomenon becoming rapidly and dramatically more common. The phrase was coined in its sociological use by Morton Grodzins, by analogy with the fact in physics that adding a small amount of weight to a balanced object can cause it to...
, is the value at which a very small increment for the control variable (like CO2) produces a very big change, even catastrophic, in the response variable (global warming).
The threshold points are difficult to locate, because the Earth System is very complex. Instead of defining the threshold value, the study establishes a range, and the threshold is supposed to lie inside it. The lower end of that range is defined as the boundary. Therefore it defines a safe space, in the sense that as long as we are below the boundary, we are below the threshold value. If the boundary is crossed, we enter into a danger zone.
| Planetary Boundaries | ||||||
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| Earth-system process | Control variable | Boundary value | Current value | Boundary crossed | Preindustrial value | Commentary |
| 1. Climate change Global warming Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades... |
Atmospheric carbon dioxide concentration (ppm Parts-per notation In science and engineering, the parts-per notation is a set of pseudo units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement... by volume) |
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| Alternatively: Increase in radiative forcing Radiative forcing In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative... (W Watt The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:... /m2) since the start of the industrial revolution (~1750) |
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| 2. Biodiversity loss Biodiversity Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions... |
Extinction rate (number of species Species In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are... per million per year) |
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| 3. Biogeochemical | (a) anthropogenic nitrogen removed from the atmosphere (millions of tonne Tonne The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI... s per year) |
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| 4. Ocean acidification Ocean acidification Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere.... |
Global mean saturation state of aragonite Aragonite Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3... in surface seawater (omega units) |
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| 5. Land use Land use Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It has also been defined as "the arrangements, activities and inputs people undertake in a certain land cover... |
Land surface converted to crop Crop Crop may refer to:* Crop, a plant grown and harvested for agricultural use* Crop , part of the alimentary tract of some animals* Crop , a modified whip used in horseback riding or disciplining humans... land (percent) |
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| 6. Freshwater Water crisis Water crisis is a general term used to describe a situation where the available water within a region is less than the region's demand. The term has been used to describe the availability of potable water in a variety of regions by the United Nations and other world organizations... |
Global human consumption of water Water resources Water resources are sources of water that are useful or potentially useful. Uses of water include agricultural, industrial, household, recreational and environmental activities. Virtually all of these human uses require fresh water.... (km3/yr) |
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| 7. Ozone depletion Ozone depletion Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon... |
Stratospheric ozone concentration (Dobson unit Dobson unit The Dobson unit is a unit of measurement of atmospheric ozone columnar density, which is dominated by ozone in the stratospheric ozone layer. One Dobson unit refers to a layer of ozone that would be 10 µm thick under standard temperature and pressure. For example, 300 DU of ozone brought... s) |
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| 8. Atmospheric aerosols Aerosol Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can... |
Overall particulate concentration in the atmosphere, on a regional basis | |
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| 9. Chemical pollution | Concentration of toxic substances Toxicity Toxicity is the degree to which a substance can damage a living or non-living organisms. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver... , plastics, endocrine disruptors, heavy metals Heavy metals A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,... and radioactive contamination Radioactive contamination Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places... into the environment |
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The proposed framework of planetary boundaries lays the groundwork for shifting approach to governance and management, away from the essentially sectoral analyses of limits to growth aimed at minimizing negative externaliti
Externality
In economics, an externality is a cost or benefit, not transmitted through prices, incurred by a party who did not agree to the action causing the cost or benefit...
es, toward the estimation of the safe space for human development
Sustainable development
Sustainable development is a pattern of resource use, that aims to meet human needs while preserving the environment so that these needs can be met not only in the present, but also for generations to come...
. Planetary boundaries define, as it were, the boundaries of the “planetary playing field” for humanity if major human-induced environmental change on a global scale is to be avoided
Transgressing one or more planetary boundaries may be highly damaging or even catastrophic, due to the risk of crossing thresholds that trigger non-linear, abrupt environmental change
Environmental change
Environmental change is defined as a change or disturbance of the environment by natural ecological processes, and is described in the following articles:*Climate change*Environment...
within continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
al- to planetary-scale systems. The 2009 study identified nine planetary boundaries and, drawing on current scientific understanding, the researchers proposed quantifications for seven of them. These seven are climate change (CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
concentration in the atmosphere < 350 ppm and/or a maximum change of +1 W/m2 in radiative forcing
Radiative forcing
In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...
); ocean acidification
Ocean acidification
Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....
(mean surface seawater saturation state with respect to aragonite ≥ 80% of pre-industrial
Industrial Revolution
The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...
levels); stratospheric
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...
ozone (less than 5% reduction in total atmospheric O3
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
from a pre-industrial level of 290 Dobson Unit
Dobson unit
The Dobson unit is a unit of measurement of atmospheric ozone columnar density, which is dominated by ozone in the stratospheric ozone layer. One Dobson unit refers to a layer of ozone that would be 10 µm thick under standard temperature and pressure. For example, 300 DU of ozone brought...
s); biogeochemical
Biogeochemical cycle
In ecology and Earth science, a biogeochemical cycle or substance turnover or cycling of substances is a pathway by which a chemical element or molecule moves through both biotic and abiotic compartments of Earth. A cycle is a series of change which comes back to the starting point and which can...
nitrogen (N) cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
(limit industrial and agricultural fixation of N2 to 35 Tg N/yr) and phosphorus (P) cycle
Phosphorus cycle
The phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and...
(annual P inflow to oceans not to exceed 10 times the natural background weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
of P); global freshwater use (< 4000 km3/yr of consumptive use of runoff resources); land system change (< 15% of the ice-free land surface under cropland); and the rate at which biological diversity is lost (annual rate of < 10 extinctions per million species). The two additional planetary boundaries for which the group had not yet been able to determine a boundary level are chemical pollution and atmospheric aerosol loading
Air pollution
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....
.
Safe operating space
Debate on the framework
The framework of planetary boundaries and the associated planetary safety zone is new and evolving. It is drawing strong responses from scientists and advisors.Christopher Field
Christopher Field
Dr. Christopher Field is a scientist and researcher, who has contributed to the field of climate change. The author of more than 200 scientific publications, Field’s research emphasizes impacts of climate change, from the molecular to the global scale...
, director of the Carnegie Institution's Department of Global Ecology, is impressed: "This kind of work is critically important. Overall, this is an impressive attempt to define a safety zone." But the conservation biologist Stuart Pimm
Stuart Pimm
Stuart Pimm is an American-British biologist and theoretical ecologist specializing in scientific research of biodiversity and conservation biology.- Professional career :...
is not impressed: "I don’t think this is in any way a useful way of thinking about things… The notion of a single boundary is just devoid of serious content. In what way is an extinction rate 10 times the background rate acceptable?" and the environmental policy analyst Bill Clark
William C. Clark
William C. Clark is an American ecologist and environmental policy analyst, and Harvey Brooks Professor of International Science, Public Policy and Human Development at the John F...
thinks: "Tipping points in the earth system are dense, unpredictable... and unlikely to be avoidable through early warning indicators. It follows that... 'safe operating spaces' and 'planetary boundaries' are thus highly suspect and potentially the new 'opiates'."
The biogeochemist William Schlesinger
William H. Schlesinger
William H. Schlesinger is a biogeochemist and the president of the Cary Institute of Ecosystem Studies, an independent not-for-profit environmental research organization in Millbrook, New York. He assumed this position after 27 years on the faculty of Duke University, where he served as the Dean...
queries whether thresholds are a good idea for pollutions at all. He thinks waiting until we near some suggested limit will just permit us to continue to a point where it is too late. "Management based on thresholds, although attractive in its simplicity, allows pernicious, slow and diffuse degradation to persist nearly indefinitely."
The hydrologist David Molden thinks planetary boundaries are a welcome new approach in the 'limits to growth' debate. "As a scientific organizing principle, the concept has many strengths [...] the numbers are important because they provide targets for policymakers, giving a clear indication of the magnitude and direction of change. They also provide benchmarks and direction for science. As we improve our understanding of Earth processes and complex inter-relationships, these benchmarks can and will be updated [...] we now have a tool we can use to help us think more deeply—and urgently—about planetary limits and the critical actions we have to take."
The ocean chemist Peter Brewer queries whether it is "truly useful to create a list of environmental limits without serious plans for how they may be achieved [...] they may become just another stick to beat citizens with. Disruption of the global nitrogen cycle is one clear example: it is likely that a large fraction of people on Earth would not be alive today without the artificial production of fertilizer. How can such ethical and economic issues be matched with a simple call to set limits? [...] food is not optional."
The environment advisor Steve Bass says the "description of planetary boundaries is a sound idea. We need to know how to live within the unusually stable conditions of our present Holocene period and not do anything that causes irreversible environmental change […] Their paper has profound implications for future governance systems, offering some of the 'wiring' needed to link governance of national and global economies with governance of the environment and natural resources. The planetary boundaries concept should enable policymakers to understand more clearly that, like human rights and representative government, environmental change knows no borders."
The climate change policy advisor Adele Morris thinks that price-based policies are also needed to avoid political and economic thresholds. "Staying within a 'safe operating space' will require staying within all the relevant boundaries, including the electorate’s willingness to pay."
In 2011, at their second meeting, the High-level Panel on Global Sustainability of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
incorporated the concept of planetary boundaries into their framework, stating that their goal was: "To eradicate poverty and reduce inequality, make growth inclusive, and production and consumption more sustainable while combating climate change and respecting the range of other planetary boundaries."
Elsewhere in their proceedings, panel members have expressed reservations about the political effectiveness of using the concept of "planetary boundaries" : "Planetary boundaries are still an evolving concept that should be used with caution […] The planetary boundaries question can be divisive as it can be perceived as a tool of the “North” to tell the “South” not to follow the resource intensive and environmentally destructive development pathway that rich countries took themselves… This language is unacceptable to most of the developing countries as they fear that an emphasis on boundaries would place unacceptable brakes on poor countries."
However, the concept is routinely used in the proceedings of the United Nations, and in the UN Daily News. For example, the UNEP Executive Director Achim Steiner
Achim Steiner
Achim Steiner is a German expert in environmental politics. From 2001 to 2006 he was Director General of the International Union for Conservation of Nature and Natural Resources...
states that the challenge of agriculture is to "feed a growing global population without pushing humanity's footprint
Ecological footprint
The ecological footprint is a measure of human demand on the Earth's ecosystems. It is a standardized measure of demand for natural capital that may be contrasted with the planet's ecological capacity to regenerate. It represents the amount of biologically productive land and sea area necessary to...
beyond planetary boundaries." The United Nations Environment Programme
United Nations Environment Programme
The United Nations Environment Programme coordinates United Nations environmental activities, assisting developing countries in implementing environmentally sound policies and practices. It was founded as a result of the United Nations Conference on the Human Environment in June 1972 and has its...
(UNEP) Yearbook 2010 also repeated Rockström's message, conceptually linking it with ecosystem management
Ecosystem management
Ecosystem management is a process that aims to conserve major ecological services and restore natural resources while meeting the socioeconomic, political and cultural needs of current and future generations. The principal objective of ecosystem management is the efficient maintenance, and ethical...
and environmental governance indicators
Sustainable Governance Indicators
The Sustainable Governance Indicators , first published in spring 2009 and updated in 2011, analyze and compare the need for reform in Organisation for Economic Co-operation and Development member countries, as well as each country's ability to respond to current social and political challenges...
.
The planetary boundaries concept is also used in proceedings by the European Commission
European Commission
The European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
, and was referred to in the European Environment Agency
European Environment Agency
European Environment Agency is an agency of the European Union. Its task is to provide sound, independent information on the environment. It is a major information source for those involved in developing, adopting, implementing and evaluating environmental policy, and also the general public...
synthesis report The European environment – state and outlook 2010.
Debate on the boundaries
There is debate about which boundaries are most relevant, and how or whether they can be usefully quantified.Climate change
Radiative forcingRadiative forcing
In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...
is a measure of the difference between the incoming radiation energy
Irradiance
Irradiance is the power of electromagnetic radiation per unit area incident on a surface. Radiant emittance or radiant exitance is the power per unit area radiated by a surface. The SI units for all of these quantities are watts per square meter , while the cgs units are ergs per square centimeter...
and the outgoing radiation energy acting across the boundary of the earth. Positive radiative forcing results in warming. From the start of the industrial revolution in 1750 to 2005, the increase in atmospheric carbon dioxide has led to a positive radiative forcing, averaging about 1.66 W
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
/m².
The climate scientist Myles Allen
Myles Allen
Myles R. Allen is head of the Climate Dynamics group at the University of Oxford's Atmospheric, Oceanic and Planetary Physics Department. He is the Principal Investigator of the distributed computing project Climateprediction.net , and was principally responsible for starting this project.He has...
thinks setting "a limit on long-term atmospheric carbon dioxide concentrations merely distracts from the much more immediate challenge of limiting warming to 2 °C." He says the concentration of carbon dioxide is not a control variable we can "meaningfully claim to control", and he questions whether keeping carbon dioxide levels below 350 ppm will avoid more than 2 °C of warming.
Adele Morris, policy director, Climate and Energy Economics Project, Brookings Institution
Brookings Institution
The Brookings Institution is a nonprofit public policy organization based in Washington, D.C., in the United States. One of Washington's oldest think tanks, Brookings conducts research and education in the social sciences, primarily in economics, metropolitan policy, governance, foreign policy, and...
, makes a criticism from the economical-political point of view. She puts emphasis in choosing policies that minimize costs and preserve consensus. She favors a system of green-house gas emissions tax
Carbon tax
A carbon tax is an environmental tax levied on the carbon content of fuels. It is a form of carbon pricing. Carbon is present in every hydrocarbon fuel and is released as carbon dioxide when they are burnt. In contrast, non-combustion energy sources—wind, sunlight, hydropower, and nuclear—do not...
, and emissions trading
Emissions trading
Emissions trading is a market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants....
, as ways to prevent global warming. She thinks that too-ambitious objectives, like the boundary limit on CO2, may discourage such actions.
Biodiversity loss
According to the biologist Cristián SamperCristián Samper
Cristián T. Samper Kutschbach is a Colombian-American biologist and Director of the Smithsonian Institution's National Museum of Natural History. He was acting secretary of the Smithsonian from 2007 to 2008, the first Latin American to hold the position.-Career:Samper graduated in 1987 from the...
, a " boundary that expresses the probability of families of species disappearing over time would better reflect our potential impacts on the future of life on Earth."
The conservation ecologist Gretchen Daily claims that "it is time to confront the hard truth that traditional approaches to conservation, taken alone, are doomed to fail. Nature reserves are too small, too few, too isolated and too subject to change to support more than a tiny fraction of Earth’s biodiversity. The challenge is to make conservation attractive—from economic and cultural perspectives. We cannot go on treating nature like an all-you-can-eat buffet. We depend on nature for food security, clean water, climate stability, seafood, timber, and other biological and physical services. To maintain these benefits, we need not just remote reserves but places everywhere—more like 'ecosystem service stations.' A few pioneers are integrating conservation and human development. The Costa Rican government is paying landowners for ecosystem services from tropical forests, including carbon offsets, hydropower production, biodiversity conservation and scenic beauty. China is investing $100 billion in “ecocompensation,” including innovative policy and finance mechanisms that reward conservation and restoration. The country is also creating “ecosystem function conservation areas” that make up 18 percent of its land area. Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
and South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
have made dramatic policy changes, too. Three advances would help the rest of the world scale such models of success. One: new science and tools to value and account for natural capital, in biophysical, economic and other terms [...] Two: compelling demonstrations of such tools in resource policy. Three: cooperation among governments, development organizations, corporations and communities to help nations build more durable economies while also maintaining critical ecosystem services."
Biogeochemical
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
has been disturbed even more than the carbon cycle. "Human activities now convert more nitrogen from the atmosphere into reactive forms than all of the Earth´s terrestrial processes combined. Much of this new reactive nitrogen pollutes waterways and coastal zones, is emitted back to the atmosphere in changed forms, or accumulates in the terrestrial biosphere." Only a small part of the fertilizers applied in agriculture is used by plants. Most of the nitrogen and phosphorus ends up in rivers, lakes and the sea, where excess amounts stress aquatic ecosystems. For example, fertilizer which discharges from rivers into the Gulf of Mexico has damaged shrimp fisheries
Shrimp fishery
A shrimp fishery is a fishery directed toward harvesting either shrimp or prawns. .-Commercial shrimping:...
because of hypoxia
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
.
The biogeochemist William Schlesinger
William H. Schlesinger
William H. Schlesinger is a biogeochemist and the president of the Cary Institute of Ecosystem Studies, an independent not-for-profit environmental research organization in Millbrook, New York. He assumed this position after 27 years on the faculty of Duke University, where he served as the Dean...
thinks waiting until we near some suggested limit for nitrogen deposition and other pollutions will just permit us to continue to a point where it is too late. He says the boundary suggested for phosphorus is not sustainable, and would exhaust the known phosphorus reserves in less than 200 years.
With regard to nitrogen, the biogeochemist and ecosystem scientist Robert Howarth says: "Human activity has greatly altered the flow of nitrogen across the globe. The single largest contributor is fertilizer use. But the burning of fossil fuels actually dominates the problem in some regions, such as the northeastern U.S. The solution in that case is to conserve energy and use it more efficiently. Hybrid vehicles are another excellent fix; their nitrogen emissions are significantly less than traditional vehicles because their engines turn off while the vehicle is stopped. (Emissions from conventional vehicles actually rise when the engine is idling.) Nitrogen emissions from U.S. power plants could be greatly reduced, too, if plants that predate the Clean Air Act and its amendments were required to comply; these plants pollute far out of proportion to the amount of electricity they produce. In agriculture, many farmers could use less fertilizer, and the reductions in crop yields would be small or nonexistent. Runoff from corn fields is particularly avoidable because corn’s roots penetrate only the top few inches of soil and assimilate nutrients for only two months of the year. In addition, nitrogen losses can be reduced by 30 percent or more if farmers plant winter cover crops, such as rye or wheat, which can help the soil hold nitrogen. These crops also increase carbon sequestration in soils, mitigating climate change. Better yet is to grow perennial plants such as grasses rather than corn; nitrogen losses are many times lower. Nitrogen pollution from concentrated animal feeding operations (CAFOs) is a huge problem. As recently as the 1970s, most animals were fed local crops, and the animals’ wastes were returned to the fields as fertilizer. Today most U.S. animals are fed crops grown hundreds of miles away, making it “uneconomical” to return the manure. The solution? Require CAFO owners to treat their wastes, just as municipalities must do with human wastes. Further, if we ate less meat, less waste would be generated and less synthetic fertilizer would be needed to grow animal feed. Eating meat from animals that are range-fed on perennial grasses would be ideal. The explosive growth in the production of ethanol as a biofuel is greatly aggravating nitrogen pollution. Several studies have suggested that if mandated U.S. ethanol targets are met, the amount of nitrogen flowing down the Mississippi River and fueling the Gulf of Mexico dead zone may increase by 30 to 40 percent. The best alternative would be to forgo the production of ethanol from corn. If the country wants to rely on biofuels, it should instead grow grasses and trees and burn these to co-generate heat and electricity; nitrogen pollution and greenhouse gas emissions would be much lower."
The ocean engineer David Vaccari says that the "most sustainable flow of phosphorus through the environment would be the natural flux: seven million metric tons per year (Mt/yr). To hit that mark yet satisfy our usage of 22 Mt/yr, we would have to recycle or reuse 72 percent of our phosphorus […] The flow could be reduced with existing technologies… [lowering] the loss to waterways from 22 to 8.25 Mt/yr, not very much above the natural flux."
Ocean acidification
Surface ocean acidity has increased thirty percent since the industrial revolution. About one quarter of the additional carbon dioxide generated by humans is dissolved in the oceans, where it forms carbonic acidCarbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...
. This acidity inhibits the ability of corals, shellfish and plankton to build shells and skeletons. Knock-on effects
Cascade effect (ecology)
An ecological cascade effect is a series of secondary extinctions that is triggered by the primary extinction of a key species in an ecosystem. Secondary extinctions are likely to occur when the threatened species are: dependent on a few specific food sources, mutualistic, or forced to coexist...
could have serious consequences for fish stock
Fish stock
Fish stocks are subpopulations of a particular species of fish, for which intrinsic parameters are the only significant factors in determining population dynamics, while extrinsic factors are considered to be insignificant.-The stock concept:All species have geographic limits to their...
s. This boundary is clearly interconnected with the climate change boundaries, since the concentration of carbon dioxide in the atmosphere is also the underlying control variable for the ocean acidification boundary.
The ocean chemist Peter Brewer thinks "ocean acidification has impacts other than simple changes in pH, and these may need boundaries too."
The marine chemist Scott Doney thinks "the main tactics are raising energy efficiency, switching to renewable and nuclear power, protecting forests and exploring carbon sequestration technologies. Regionally, nutrient runoff to coastal waters not only creates dead zones but also amplifies acidification. The excess nutrients cause more phytoplankton to grow, and as they die the added CO2 from their decay acidifies the water. We have to be smarter about how we fertilize fields and lawns and treat livestock manure and sewage […] Locally, acidic water could be buffered with limestone or chemical bases produced electrochemically from seawater and rocks. More practical may be protecting specific shellfish beds and aquaculture fisheries. Larval mollusks such as clams and oysters appear to be more susceptible to acidification than adults, and recycling old clamshells into the mud may help buffer pH and provide better substrate for larval attachment. The drop in ocean pH is expected to accelerate in coming decades, so marine ecosystems will have to adapt. We can enhance their chances for success by reducing other insults such as water pollution and overfishing, making them better able to withstand some acidification while we transition away from a fossil-fuel energy economy."
Land use
Across the planet, forests, wetlands and other vegetation types are being converted to agricultural and other land useLand use
Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It has also been defined as "the arrangements, activities and inputs people undertake in a certain land cover...
s, impacting freshwater, carbon and other cycles, and reducing biodiversity.
The environment advisor Steve Bass says research tells us that "the sustainability of land use depends less on percentages and more on other factors. For example, the environmental impact of 15 per cent coverage by intensively farmed cropland in large blocks will be significantly different from that of 15 per cent of land farmed in more sustainable ways, integrated into the landscape. The boundary of 15 per cent land-use change is, in practice, a premature policy guideline that dilutes the authors' overall scientific proposition. Instead, the authors might want to consider a limit on soil degradation or soil loss. This would be a more valid and useful indicator of the state of terrestrial health."
The Earth systems scientist Eric Lambin thinks that "intensive agriculture should be concentrated on land that has the best potential for high-yield crops […] We can avoid losing the best agricultural land by controlling land degradation, freshwater depletion and urban sprawl. This step will require zoning and the adoption of more efficient agricultural practices, especially in developing countries. The need for farmland can be lessened, too, by decreasing waste along the food distribution chain, encouraging slower population growth, ensuring more equitable food distribution worldwide and significantly reducing meat consumption in rich countries."
Freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
systems are having dramatic effects
Water crisis
Water crisis is a general term used to describe a situation where the available water within a region is less than the region's demand. The term has been used to describe the availability of potable water in a variety of regions by the United Nations and other world organizations...
. The freshwater cycle
Water cycle
The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Water can change states among liquid, vapor, and solid at various places in the water cycle...
is another boundary significantly affected by climate change. Freshwater resources, such as lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s and aquifer
Aquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
s, are usually renewable resources which naturally recharge (the term fossil water
Fossil water
Fossil water or paleowater is groundwater that has remained sealed in an aquifer for a long period of time. Water can rest underground in "fossil aquifers" for thousands or even millions of years...
is sometimes used to describe aquifers which don't recharge). Overexploitation
Overexploitation
Overexploitation, also called overharvesting, refers to harvesting a renewable resource to the point of diminishing returns. Sustained overexploitation can lead to the destruction of the resource...
occurs if a water resource is mined or extracted at a rate that exceeds the recharge rate. Recharge usually comes from area streams, rivers and lakes. Forests enhance the recharge of aquifers in some locales, although generally forests are a major source of aquifer depletion
Overdrafting
Overdrafting is the process of extracting groundwater beyond the safe yield or equilibrium yield of the aquifer.Since every groundwater basin recharges at a different rate depending upon precipitation, vegetative cover and soil conservation practises, the quantity of groundwater that can be safely...
. Depleted aquifers can become polluted with contaminants such as nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
s, or permanently damaged through subsidence or through saline intrusion from the ocean. This turns much of the world's underground water and lakes into finite resources with peak usage debates similar to oil
Peak oil
Peak oil is the point in time when the maximum rate of global petroleum extraction is reached, after which the rate of production enters terminal decline. This concept is based on the observed production rates of individual oil wells, projected reserves and the combined production rate of a field...
. Though Hubbert's original analysis did not apply to renewable resources, their overexploitation can result in a Hubbert-like peak. A modified Hubbert curve
Hubbert curve
The Hubbert curve is an approximation of the production rate of a resource over time. It is a symmetric logistic distribution curve, often confused with the "normal" gaussian function. It first appeared in "Nuclear Energy and the Fossil Fuels," geophysicist M...
applies to any resource that can be harvested faster than it can be replaced.
The hydrologist Peter Gleick
Peter Gleick
Dr. Peter H. Gleick is a scientist working on issues related to the environment, economic development, and international security, with a focus on global freshwater challenges. He works at the Pacific Institute in Oakland, California, which he co-founded in 1987. In 2003 he was awarded a MacArthur...
comments: "Few rational observers deny the need for boundaries to freshwater use. More controversial is defining where those limits are or what steps to take to constrain ourselves within them. Another way to describe these boundaries is the concept of peak water
Peak water
The term Peak Water has been put forward as a concept to help understand growing constraints on the availability, quality, and use of freshwater resources...
. Three different ideas are useful. 'Peak renewable' water limits are the total renewable flows in a watershed. Many of the world’s major rivers are already approaching this threshold—when evaporation and consumption surpass natural replenishment from precipitation and other sources. 'Peak nonrenewable' limits apply where human use of water far exceeds natural recharge rates, such as in fossil groundwater basins of the Great Plains, Libya, India, northern China and parts of California’s Central Valley. 'Peak ecological' water is the idea that for any hydrological system, increasing withdrawals eventually reach the point where any additional economic benefit of taking the water is outweighed by the additional ecological destruction that causes. Although it is difficult to quantify this point accurately, we have clearly passed the point of peak ecological water in many basins around the world where huge damage has occurred […] The good news is that the potential for savings, without hurting human health or economic productivity, is vast. Improvements in water-use efficiency are possible in every sector. More food can be grown with less water (and less water contamination) by shifting from conventional flood irrigation to drip and precision sprinklers, along with more accurately monitoring and managing soil moisture. Conventional power plants can change from water cooling to dry cooling, and more energy can be generated by sources that use extremely little water, such as photovoltaics and wind."
The hydrologist David Molden says "a global limit on water consumption is necessary, but the suggested planetary boundary of 4,000 cubic kilometres per year is too generous."
Ozone depletion
Ozone layer
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...
protectively filters ultraviolet radiation (UV) from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, which would otherwise damage biological systems. The actions taken after the Montreal Protocol
Montreal Protocol
The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion...
appeared to be keeping the planet within a safe boundary. However in 2011, according to a paper published in Nature, the boundary was unexpectedly pushed in the Arctic; "... the fraction of the Arctic vortex in March with total ozone less than 275 Dobson units (DU) is typically near zero, but reached nearly 45%".
The Nobel laureate in chemistry, Mario Molina
Mario J. Molina
Mario José Molina-Pasquel Henríquez is a Mexican chemist and one of the most prominent precursors to the discovering of the Antarctic ozone hole. He was a co-recipient Mario José Molina-Pasquel Henríquez (born March 19, 1943 in Mexico City) is a Mexican chemist and one of the most prominent...
, says "five per cent is a reasonable limit for acceptable ozone depletion, but it doesn't represent a tipping point".
The physicist David Fahey says that as a result of the Montreal Protocol "stratospheric ozone depletion will largely reverse by 2100. The gain has relied, in part, on intermediate substitutes, notably hydrochlorofluorocarbons (HCFCs), and the growing use of compounds that cause no depletion, such as hydrofluorocarbons (HFCs). Ongoing success depends on several steps:
- "Continue observing the ozone layer to promptly reveal unexpected changes. Ensure that nations adhere to regulations; for example, the HCFC phaseout will not be complete until 2030.
- "Maintain the Scientific Assessment Panel under the protocol. It attributes causes of changes in the ozone layer and evaluates new chemicals for their potential to destroy ozone and contribute to climate change.
- "Maintain the Technology and Economic Assessment Panel. It provides information on technologies and substitute compounds that helps nations assess how the demand for applications such as refrigeration, air-conditioning and foam insulation can be met while protecting the ozone layer.
"The two panels will also have to evaluate climate change and ozone recovery together. Climate change affects ozone abundance by altering the chemical composition and dynamics of the stratosphere, and compounds such as HCFCs and HFCs are greenhouse gases. For example, the large projected demand for HFCs could significantly contribute to climate change."
Atmospheric aerosols
AerosolAerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...
particles in the atmosphere impact the health of humans and influence monsoon
Monsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
and global atmospheric circulation
Atmospheric circulation
Atmospheric circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth....
systems. Some aerosols produce clouds which cool the Earth by reflecting sunlight back to space, while others, like soot, produce thin clouds in the upper stratosphere which behave like a greenhouse, warming the Earth. On balance, anthropogenic aerosols probably produce a net negative radiative forcing
Radiative forcing
In climate science, radiative forcing is generally defined as the change in net irradiance between different layers of the atmosphere. Typically, radiative forcing is quantified at the tropopause in units of watts per square meter. A positive forcing tends to warm the system, while a negative...
(cooling influence). Worldwide each year, aerosol particles result in about 800,000 premature deaths. Aerosol loading is sufficiently important to be included among the planetary boundaries, but it is not yet clear whether an appropriate safe threshold measure can be identified.
Chemical pollution
Some chemicals, such as persistent organic pollutants, heavy metals and radionuclideRadionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
s, have potentially irreversible additive
Bioaccumulation
Bioaccumulation refers to the accumulation of substances, such as pesticides, or other organic chemicals in an organism. Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at which the substance is lost...
and synergic effects on biological organisms, reducing fertility and resulting in permanent genetic damage. Sublethal uptakes are drastically reducing marine bird and mammal populations. This boundary seems important, although it is hard to quantify.
A Bayesian emulator for persistent organic pollutants has been developed which can potentially be used to quantify the boundaries for chemical pollution.
Interaction among boundaries
The boundary values above were set on the assumption that interactions are not occurring if other boundaries are being crossed. However, a given planetary boundary may interact in a manner that changes the safe operating level of other boundaries. Rockström et al. did not analyze such interactions, but they suggested that many of these interactions will reduce rather than expand the proposed boundary levels.For example, the land use
Land use
Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It has also been defined as "the arrangements, activities and inputs people undertake in a certain land cover...
boundary could shift downward if the freshwater boundary is breached, causing lands to become arid and unavailable for agriculture. At a regional level, water resources may decline in Asia if deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
continues in the Amazon
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...
. Such considerations suggest the need for "extreme caution in approaching or transgressing any individual planetary boundaries."
Another example has to do with coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s and marine ecosystem
Marine ecosystem
Marine ecosystems are among the largest of Earth's aquatic ecosystems. They include oceans, salt marsh and intertidal ecology, estuaries and lagoons, mangroves and coral reefs, the deep sea and the sea floor. They can be contrasted with freshwater ecosystems, which have a lower salt content. Marine...
s. In 2009, showed that, since 1990, calcification in the reefs of the Great Barrier
Great Barrier Reef
The Great Barrier Reef is the world'slargest reef system composed of over 2,900 individual reefs and 900 islands stretching for over 2,600 kilometres over an area of approximately...
that they examined decreased at a rate unprecedented over the last 400 years (14% in less than 20 years). Their evidence suggests that the increasing temperature stress and the declining ocean saturation state of aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
is making it difficult for reef corals to deposit calcium carbonate. explored how multiple stressors, such as increased nutrient loads and fishing pressure, move corals into less desirable ecosystem states. showed that ocean acidification will significantly change the distribution and abundance of a whole range of marine life, particularly species "that build skeletons, shells, and tests of biogenic calcium carbonate. "Increasing temperatures, surface UV radiation levels and ocean acidity all stress marine biota
Biota (ecology)
Biota are the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biota of the Earth lives in the biosphere.-See...
, and the combination of these stresses may well cause perturbations in the abundance and diversity of marine biological systems that go well beyond the effects of a single stressor acting alone."
See also
- Carbon cycle re-balancingCarbon cycle re-balancingThe carbon cycle is the process by which carbon is exchanged between the four reservoirs of carbon: the biosphere, the earth, the air and water. Exchanges take place in several ways, including respiration, transpiration, combustion, and decomposition...
- Holocene extinction
- Human impacts on the nitrogen cycleHuman impacts on the nitrogen cycleHuman impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen inputs to the environment currently exceed inputs from natural N fixation. As a consequence of anthropogenic inputs, the global nitrogen cycle has been significantly altered over the past century...
- Hydrological cycle
- Nitrogen cycleNitrogen cycleThe nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...
- Phosphorus cyclePhosphorus cycleThe phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movement of phosphorus, because phosphorus and...
- Planetary managementPlanetary managementPlanetary management is intentional global-scale management of Earth's biological, chemical and physical processes and cycles . Planetary management also includes managing humanity’s influence on planetary-scale processes...
Further reading
- Foster JB, Clark B and York R (2010) The Ecological Rift: Capitalism's War on the Earth Monthly ReviewMonthly ReviewMonthly Review is an independent Marxist journal published 11 times per year in New York City.-History:The publication was founded by Harvard University economics instructor Paul Sweezy, who became the first editor...
Press, ISBN 9781583672198. - Richardson K, Steffen W, and Liverman D (2011) Climate Change: Global Risks, Challenges and Decisions Cambridge University PressCambridge University PressCambridge University Press is the publishing business of the University of Cambridge. Granted letters patent by Henry VIII in 1534, it is the world's oldest publishing house, and the second largest university press in the world...
, pp. 485–487. ISBN 9780521198363. - Garver G (2011) "A Framework for Novel and Adaptive Governance Approaches Based on Planetary Boundaries" Colorado State UniversityColorado State UniversityColorado State University is a public research university located in Fort Collins, Colorado. The university is the state's land grant university, and the flagship university of the Colorado State University System.The enrollment is approximately 29,932 students, including resident and...
, Colorado Conference on Earth System Governance, 17–20 May 2011. - Folke C and Gunderson L (2010) "Resilience and Global Sustainability" Ecology and Society, 15(4): 43.
- Geisler C (2010) "Must Biodiversity Hot-Spots Be Social Not-Spots? Win-Win Ecology as Sustainable Social Policy" Consilience: The Journal of Sustainable Development, 4(1): 119–133.
- Jack Horner (2010) "A Dynamical Implementation of the Stockholm Resilience Center Safe Operating Space Model" In Proceedings of the 2010 International Conference on Scientific Computing, CSC 2010, pages 236-242. Eds. HR Arabnia et al. July 12–15, 2010, Nevada, CSREA Press. ISBN 1-60132-137-6.
- Richardson K (2010) Biodiversity, a global threshold orgprints.org.
- J Rockström J (2010) Planetary Boundaries New Perspectives Quarterly, 27(1): 72–74.
- Rockström J and Karlberg L (2010) "The Quadruple Squeeze: Defining the safe operating space for freshwater use to achieve a triply green revolution in the Anthropocene" AMBIO: A Journal of the Human Environment 39(3): 257–265.
- Steffen W, Grinevald J, Crutzen P and McNeill J (2011) "The Anthropocene: conceptual and historical perspective" Philosophical Transactions of the Royal Society A: Physical, Mathematical and Engineering SciencesPhilosophical Transactions of the Royal Society A: Physical, Mathematical and Engineering SciencesPhilosophical Transactions of the Royal Society A: Physical, Mathematical and Engineering Sciences is a peer-reviewed scientific journal published by the Royal Society. It was originally published as Philosophical Transactions of the Royal Society, but was split into two journals in 1887. Phil....
, 369(1938):842–867. - Moldana B, Svatava Janoušková S and Tomáš Háka T (2011) "How to understand and measure environmental sustainability: Indicators and targets" ScienceDirectScienceDirectScienceDirect is one of the largest online collections of published scientific research in the world. It is operated by the publisher Elsevier and contains nearly 10 million articles from over 2,500 journals and over 6,000 e-books, reference works, book series and handbooks issued by Elsevier...
. - Establishing Environmental Sustainability Thresholds and Indicators Ecologic Institute and Sustainable Europe Research Institute (SERI) , Final report to the European CommissionEuropean CommissionThe European Commission is the executive body of the European Union. The body is responsible for proposing legislation, implementing decisions, upholding the Union's treaties and the general day-to-day running of the Union....
’s DG EnvironmentDirectorate-General for the Environment (European Commission)The Directorate-General for the Environment is a Directorate-General of the European Commission, responsible for the European Union policy area of the environment....
, November 2010. - From ocean to ozone: Earth's nine life-support systems New ScientistNew ScientistNew Scientist is a weekly non-peer-reviewed English-language international science magazine, which since 1996 has also run a website, covering recent developments in science and technology for a general audience. Founded in 1956, it is published by Reed Business Information Ltd, a subsidiary of...
, issue 2749, 24 February 2010. - Living in the Anthropocene: Toward a New Global Ethos Paul J. CrutzenPaul J. CrutzenPaul Jozef Crutzen is a Dutch Nobel prize winning atmospheric chemist.Crutzen is best known for his research on ozone depletion. He lists his main research interests as “Stratospheric and tropospheric chemistry, and their role in the biogeochemical cycles and climate”...
and Christian Schwägerl, Yale Environment 360, 22 February 2011. - The Anthropocene Debate: Marking Humanity’s Impact Elizabeth KolbertElizabeth KolbertElizabeth Kolbert is an American journalist and author. She is best known for her 2006 book Field Notes from a Catastrophe, and as an observer and commentator on environmentalism for The New Yorker magazine.-Youth and education:...
, Yale Environment 360, 17 May 2010. - Planetary Boundaries and the New Generation Gap Alex SteffenAlex SteffenAlex Steffen is an American writer, editor, public speaker and futurist most noted for his bright green ideas.Steffen co-founded and ran the online magazine Worldchanging from its start in 2003 until its closure in 2010...
, WorldchangingWorldchangingWorldchanging is an American non-profit online magazine and blog about sustainability and social innovation. At 19/09/2011, it was taken over by Architecture for Humanity....
, 30 June 2009. - Djoghlaf AAhmed DjoghlafAhmed Djoghlaf , is the Executive Secretary of the Convention on Biological Diversity under the United Nations Environment Programme ....
and Dodds FFelix DoddsFelix Dodds is an author, futurist and activist. He has been instrumental in developing new modes of stakeholder engagement with the United Nations, particularly within the field of sustainable development. Mr. Dodds is the Executive Director of Stakeholder Forum for a Sustainable Future...
(Eds.) (2011) Biodiversity and Ecosystem Insecurity: A Planet in Peril Earthscan. ISBN 9781849712200. - Geisler C (2010) "Must Biodiversity Hot-Spots Be Social Not-Spots? Win-Win Ecology as Sustainable Social Policy" Consilience: The Journal of Sustainable Development, 4(1): 119–133.
- Victor P (2010) "Questioning economic growth" Nature, 468: 370–371.
- Sustainable Developments - Transgressing Planetary Boundaries Jeffrey D. Sachs, Scientific American, December 2009, 301(6):36.
- "Boundaries for a Healthy Planet" by Foley J, Daily GC, Howarth R, Vaccari DA, Morris AC, Lambin EF, Doney SC, Peter H. GleickPeter GleickDr. Peter H. Gleick is a scientist working on issues related to the environment, economic development, and international security, with a focus on global freshwater challenges. He works at the Pacific Institute in Oakland, California, which he co-founded in 1987. In 2003 he was awarded a MacArthur...
and Fahey DW. Scientific American, April 2010. Includes opinion essays by invited experts on the planetary boundaries. - Scheffer M, Bascompte J, Brock WA, Brovkin V, Carpenter SRStephen R. CarpenterStephen Russell Carpenter is an American limnologist.-Education and Career:Carpenter received his B.A. from Amherst College , M.S. from the University of Wisconsin—Madison , and Ph.D. from the University of Wisconsin, Madison...
, Dakos V, Held H, van Nes EH, Rietkerk M and Sugihara G (2009) "Early-warning signals for critical transitions" Nature, 461: 53–59. - Lenton TMTim Lenton-References:...
, Held H, Kriegler E, Jim W. Hall JW, Lucht W, Rahmstorf S and Schellnhuber HJ (2008) "Tipping elements in the Earth’s climate system" PNAS,105(6): 1786–1793. (Precursor elements?) - Meadows DH, Randers J and Meadows DL (2005) Limits to growth: the 30-year update Edition 3, revised, Earthscan. ISBN 9781844071449.
- "Prophesy of economic collapse 'coming true'", by Jeff Hecht, NewScientist, 17 November 2008.
- Foster JBJohn Bellamy FosterJohn Bellamy Foster is a professor of sociology at the University of Oregon and also editor of Monthly Review, an independent socialist magazine. His writings have focused on political economy, environmental sociology, and Marxist theory...
, Clark BBrett Clark (sociologist)Brett Clark is an assistant professor of sociology at North Carolina State University. His areas of interest are ecology, political economy and science.-Works and awards:...
and York R (2010) The Ecological Rift: Capitalism's War on the Earth Monthly Review Press. ISBN 9781583672198. Review - Lynas, MMark LynasMark Lynas is a British author, journalist and environmental activist who focuses on climate change. He is a contributor to New Statesman, Ecologist, Granta and Geographical magazines, and The Guardian and The Observer newspapers in the UK; he also worked on the film The Age of Stupid...
(2011) The God Species: How the planet can survive the age of humans HarperCollinsHarperCollinsHarperCollins is a publishing company owned by News Corporation. It is the combination of the publishers William Collins, Sons and Co Ltd, a British company, and Harper & Row, an American company, itself the result of an earlier merger of Harper & Brothers and Row, Peterson & Company. The worldwide...
. ISBN 9780007313426. – a new book based on the concept of planetary boundaries, by the 2008 winner of the Royal Society Prize for Science Books. Review Review2
External links
- Tipping towards the unknown Stockholm Resilience CentreStockholm Resilience CentreThe Stockholm Resilience Centre is an international research centre at Stockholm University that focuses on the resilience of social-ecological systems....
, 23 September 2009. - Planetary Boundaries: Specials NatureNature (journal)Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
, 24 september 2009. - Johan Rockstrom: Let the environment guide our development TEDTED (conference)TED is a global set of conferences owned by the private non-profit Sapling Foundation, formed to disseminate "ideas worth spreading"....
video, July 2010. Transcript html - Vidoes with Will Steffen and Jeffrey D. Sachs
- UN Debates Holistic Approach to Sustainable Development ABCLive.In, 21 April 2011 – the term "planetary boundaries" is starting to shape debates, such as this one.
- A Planet on the edge Global Change, 2009, 74: 10–13. Featured cover story, via ScribdScribdScribd is a Web 2.0 based document-sharing website which allows users to post documents of various formats, and embed them into a web page using its iPaper format. Scribd was founded by Trip Adler, Tikhon Bernstam, and Jared Friedman in 2006...
. - Welcome to the Anthropocene The EconomistThe EconomistThe Economist is an English-language weekly news and international affairs publication owned by The Economist Newspaper Ltd. and edited in offices in the City of Westminster, London, England. Continuous publication began under founder James Wilson in September 1843...
, May 26 May 2011. - The Anthropocene: A man-made world The Economist, May 26 May 2011.
- Has the green movement lost its way? The Guardian, 2 July 2011.
- Critical comment