Biodiversity & Ecological Succession

  • Some ecosystems are more sustainable than others. Sustainable ecosystems are able to maintain their balance because they have a great deal of biodiversity.


The biodiversity of an ecosystem is the variation, or differences, among living organisms within that ecosystem. This includes genetic variation within a species as well as the variety of different species within an ecosystem. The biodiversity of an ecosystem increases with the number of different species of organisms that live in that ecosystem.
Biodiversity is not evenly distributed on Earth. Some ecosystems are more diverse than others. Usually, the more diverse that an ecosystem is, the more stable it is. Biodiversity on land is generally highest at the equator and decreases as you move toward the poles.

Rainforests have a high level of biodiversity. A large number of different and unique species live in rainforests.
Disturbances, such as disease and fire, can cause ecosystems to become unstable. When an ecosystem is disturbed, individual organisms, as well as entire species, can die out.
Ecosystems can better handle disturbances whenever there is a high amount of biodiversity within that ecosystem. The more varied the organisms within an ecosystem, the more likely it is that some of them could use their specialized and unique adaptations to survive major changes or disturbances in the ecosystem.

Ecological Succession

Ecological succession is the process by which an ecosystem undergoes a series of changes as communities of organisms change their environment and new communities of organisms move into the ecosystem. It can occur when the conditions of an ecosystem are greatly changed by a disturbance, and the ecosystem does not have enough biodiversity to remain stable. This process is usually gradual because it can take a long time for communities to become established in an ecosystem.
disturbance event
disturbance event

A drastic ecological disturbance, such as a forest fire, could cause ecological succession, as new species move in where old species once were.
In some cases, the species structure of an ecosystem is changed rapidly by a disturbance, such as a forest fire. If the ecosystem becomes unstable, primary or secondary succession can result. If succession begins in a new, unoccupied habitat where there is no soil present, it is called primary succession. Primary succession can occur after severe landslides or volcanic eruptions. If there is a disturbance in an area but soil is still present after the disturbance, this change in species structure is known as secondary succession.
Primary succession, or the development of an ecosystem in an area where life did not exist before, occurs in the following stages:
  • During succession, producers typically enter the developing ecosystem before consumers. Succession begins when the first organisms, usually lichens or mosses, colonize a bare rock. Acids from the lichens and mosses weather the rock. Eroded sediments combine with bacteria and dead lichens and mosses to form a thin layer of soil.
  • As soil forms, more and more plants are able to grow in the area. Grasses usually grow in this thin layer of soil first, followed by shrubs and, eventually, trees. This attracts insects and other animal species. Over time, the soil layer thickens and the biodiversity of the community increases.
  • After many years, a stable ecosystem develops. Often, this is a forest ecosystem. Depending on the ecosystem’s abiotic factors, however, a stable ecosystem may be a mature desert community, a coral reef, or any other kind of ecosystem on Earth. The final stage of ecological succession is called the climax community and the species in this community are in relative equilibrium.