An environmental gradient is a gradual change in abiotic factors through space (or time). Environmental gradients can be related to factors such as altitude, temperature, depth, ocean proximity and soil humidity.

Species abundance

Abundance (ecology)

Abundance is an ecological concept referring to the relative representation of a species in a particular ecosystem. It is usually measured as the large number of individuals found per sample...

s usually change along environmental gradients in a more or less predictive way. However, the species abundance along an envronmental gradient is not only determined by the abiotic factor but, also by the change in the biotic interactions along the environmental gradient.

At an ecotone

Ecotone

An ecotone is a transition area between two biomes but different patches of the landscape, such as forest and grassland. It may be narrow or wide, and it may be local or regional...

, species abundance

Abundance (ecology)

Abundance is an ecological concept referring to the relative representation of a species in a particular ecosystem. It is usually measured as the large number of individuals found per sample...

s change relatively quick compared to the environmental gradient.

The species distribution

Species distribution

Species distribution is the manner in which a biological taxon is spatially arranged. Species distribution is not to be confused with dispersal, which is the movement of individuals away from their area of origin or from centers of high population density. A similar concept is the species range. A...

 along environmental gradients has been studied intensively due to large databases of species presence data (e.g. GBIF

Global Biodiversity Information Facility

The Global Biodiversity Information Facility is an international organisation that focuses on making scientific data on biodiversity available via the Internet using web services. The data are provided by many institutions from around the world; GBIF's information architecture makes these data...

)

Environmental Gradients are linked to Connectivity and natural disturbance when considering river systems. A river restoration scheme must consider all of these factors before undertaking a program as these three factors are what leads to a larger biodiversity.

Each species are not found in every type of habitat or in every part of the world. Within the environment there are multiple factors which affects organisms. The organisms in the polar region can not survive the climate at the equator.
See also: Biome

Biome

Biomes are climatically and geographically defined as similar climatic conditions on the Earth, such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems. Some parts of the earth have more or less the same kind of abiotic and biotic factors spread over a...

, cline (biology), thermocline

Thermocline

A thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below...

.