Introduction

Reunion Island's 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...

 covers a very concentrated part of the western littoral

Littoral

The littoral zone is that part of a sea, lake or river that is close to the shore. In coastal environments the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged. It always includes this intertidal zone and is often used to...

. The close proximity to the continental shelf means that the sea quickly becomes deep not far from the coast. the coral reef is located between St Leu and St Gilles. The full GPS co-ordinates of the coral reef are: 53°32’ East and 21°7’ South. The reef is more than 9 km long, and ranges in width from 50 metres in its northern part at St Gilles to 600 metres in the south. A rich biodiversity

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...

 of fauna and flora inhabits the coral environment, sustained by the proximity of deeper ocean currents.

Environment & Threat

Coral reefs are one of the most populated places of the seas. The Reunion Island coral reef is a habitat for soft and hard corals, fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 and shellfish

Shellfish

Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater...

. The fauna is sustained because there is a lot of food like algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

, and the potential for protection from predators. The coral feed on a diet mostly composed of algae, which are caught by their tentacles. Their reproduction is limited, with only a proportion of male corals leaving some sperm cells in the water. These sperm cells are caught by female coral to reproduce.

In recent times, the coral reef of Reunion Island is threatened because of human activities. Specifically, the 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...

, and the overexploitation of the marine resources.
The visitor pressure is one of the most important reasons for the threat. Because of the pollution, the poorer water quality leads to a loss of fish biodiversity. In effect, human activities contribute to pollute the sea. The qualities of the water also have an influence on the corals. The pollution makes coral development slower and contributes to algae creation. This is harmful for corals, because algae enter in competition with these animals. Poor coral health on the Reunion Island reef is evidenced by a bleaching on colour from the organisms.
Corals are very fragile because a year is required to grow 10 centimetres of coral. Scientists think that corals could disappear because of the increase of global and local sea temperatures. Corals are very sensitive of the temperature variations. The optimum water temperature for Reunion Island coral is between 23°C and 28°C. 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...

 (and indirectly the pollution) can contribute to the extinction of coral species. Due to human activities, which may also cause global warming, the water temperature could exceed the maximum temperature for the corals.

In recent years, all the countries in the region have experienced heavy human growth pressures that are inducing reef deterioration and losses in reef resources. Natural (cyclones) and anthropogenic disturbances also affect the reefs in Reunion Island. The latter are often caused by urban development of catchment areas, which has led to an increase in nutrient levels in coral reef areas via submarine groundwater discharge (Cuet et al. 1988). As a result of the impact from increased nutrient levels, the structure of benthic communities has been modified.

Management of coral reef in Reunion Island

There is a variance of vulnerability

Vulnerability

Vulnerability refer to the susceptibility of a person, group, society, sex or system to physical or emotional injury or attack. The term can also refer to a person who lets their guard down, leaving themselves open to censure or criticism...

 that we can divide in 3 sectors:

-The less vulnerable sectors are situated in St Paul and l’Etang-Salé (North), due to the absence of reef ecosystem and the stability of the shore.

-The Moderately vulnerable sector is situated in Grande Anse and Boucan Canot, due to the pressure of urbanisation, which is feeble/moderate. Overall, it has few severe impacts.

-The Highly vulnerable points are located at la Pointe des Aigrettes, la Pointe au Sel, la Ravine Blanche, St-Pierre and Grand Bois (South)

The main causes for such vulnerability depend on four facts: the first one is the beaches that are affected by erosion, the fact that the recovery rate of coral reef flats in living corals is inferior to 50%. Then there is the question of urbanisation, which puts pressure on the soil and aggravates coastal erosion, degrades the landscape, and generates pollution. Last, the high sensibility of terrestrial and marine environment is due to poor hydrodynamic conditions.
The Dock of Pirogue and St-Pierre Ville are characterised by irreversible deterioration due to to these growing faster.

To slow down this degradation, the researchers recommend coordination of the coral reef management by draining basins in order to limit the entrance of terrestrial pollution from the island. The access, control and use of the reef is also essential, using way markers. Indeed, researchers advise banning access to of certain of the most sensitive areas. They recommend in the same way wildlife refuges, and the surveillance of fishing and leisure activities.
The “Marine Nature Reserve”, created in 2007, plays a fundamental role in the management of the coral reef’s protection. The reserve has already brought benefits by informing the people who use it. It helps to decrease the poaching and gain respect and awareness for the regulations.
The coral reef is an important source of revenue for local communities. It generates local income through fisheries and tourism. To reconcile human activities and conservation of this fragile ecosystem, both are essential to the island’s economic development. They are involved in the management of the littoral by introducing stronger access control and user regulations for the Reunion’s coral reef.

Another way to manage this coast degeneration is to measure the carrying capacity. It is in fact one of the key indicators for the coast management.
By definition, it sets the limit from which risk of irreparable degradation of the environment and the social climate are high.
It is evaluated using 45 criteria, including:
Anarchic development: the fact that construction is not planified, use of land not managed, with no regards for the local architecture which

• leads to a visual degradation of the coast.
• Increase in atmospheric pollution: due to car and boat emission.
• Increased release of waste: (wastewater or solid waste) due to the absence of appropriate infrastructure
  Infrastructure
  Infrastructure is basic physical and organizational structures needed for the operation of a society or enterprise, or the services and facilities necessary for an economy to function...
  
   to treat the addition of waste because of the cost of their installation.
• Saturation of service infrastructures during the high season.
• Habitat loss and biodiversity.
• Overconsumption of natural resources by a growing population with more demands for example water necessary for golf parks.
• Abandonment of traditional activity.
• Modification of socio cultural identities due to the change in life style.

The locals are dependent on the tourist activity. However, the population don’t benefit directly from all the related profits.

Tourism

Many activities are organized around the 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...

, and this generates money and is also an important part of the island's economy

Economy

An economy consists of the economic system of a country or other area; the labor, capital and land resources; and the manufacturing, trade, distribution, and consumption of goods and services of that area...

 after the chikungunya

Chikungunya

Chikungunya virus is an insect-borne virus, of the genus Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. There have been recent breakouts of CHIKV associated with severe illness...

 crisis. Activities include scuba diving, snorkelling, boat trips, fishing, helicopter flights, and even paragliding

Paragliding

Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure...

.
Moreover, many diving schools suggest initiation sessions (first dive), or training sessions, on these sites. In order to be more attractive, some also organize photography contests and small events to touch more categories of people than scuba divers and tourists. These activities are strongly linked to the coral reef's protection. The coral reef is a natural barrier which protects the coast and so the economy (harbors, towns..) from typhoons. Corals protect the island from the ocean's violence,

Thanks to a recent study, specialists have estimated the benefits of leisure activities such as scuba diving to be above 2 076 150 €, water sports above 118 018 €, and diving boats / submarines above 1 851 614 €. Moreover, the fact that you are on the littoral, close to the coral reef, influences the price of local housing. The closer you are from a beach protected by corals, the higher the real estate prices are.

To conclude, the coral barrier is an important resource for the Réunion Island. It also sustains the standards of living of these parts of the island, due to it's influence on prices are fixed and incomes.

Books

Montaggioni, L. , 2007, Coraux et Récifs, archives du climat., société géologique de France VUIBERT, ISBN 978-2-7117-4065-9

Magazines

• Holland, J.S., 2011, ‘Une fragile muraille’, National Geographic France, 27/09/2011, p.2
• Lison, C., 2011, ‘Rencontre sous la mer’, National Geographic France, 27/09/2011, p.24

Conference paper

P. Chabanet, L. Bigot, O. Naim, R. Garnier, E. Tessier and M. Moyne-Picard., Coral reef monitoring at Reunion island (Western Indian Ocean) using the GCRMN method, Oct.2000., Proceedings 9th International Coral Reef Symposium, Bali, Indonesia
Source: http://www.coremap.or.id/downloads/ICRS9th-Chabanl_Copy.pdf
6 pages

Saffache, P., Université des Antilles et de la Guyane, Campus de Schoelcher, Département de Géographie, From Degradation to Environmental Management: Case in Point: The Reunion Island Sea Bed, Martinique

Internet

• http://www.reunion.fr/modules/rechercher/rechercher-dans-les-services-touristiques.html
• http://coraux.univ-reunion.fr/
• http://www.liledelareunion.com/Fr/economie/index.php
• http://www.aquaportail.com/modules/news/index.php?storytopic=12&start=586
• http://coraux.univ-reunion.fr/
• http://coraux.univ-reunion.fr/spip.php?article5
• http://www.coremap.or.id/downloads/ICRS9th-Chabanl_Copy.pdf
• http://www.liledelareunion.com/
• http://www.reunion.fr/modules/rechercher/rechercher-dans-les-services-touristiques.html
• http://en.ird.fr/the-media-library/scientific-news-sheets/354-reunion-island-coral-reefs-in-poor-health
• http://vieoceane.free.fr/paf/ficheb3.html
• http://www.liledelareunion.com/Fr/economie/index.php
• http://fr.wikipedia.org/wiki/La_Réunion
• http://fr.wikipedia.org/wiki/R%C3%A9cif_corallien