ECOLOGICAL CRISIS

An ecological crisis occurs when the environment of a species or a population changes in a way that destabilizes its continued survival.

There are many possible causes of such crisis:

>  It may be that the environment quality degrades compared to the species' needs, after a change of abiotic ecological factor (for example, an increase of temperature, less significant rainfalls).

>  It may be that the environment becomes unfavourable for the survival of a species (or a population) due to an increased pressure of predation.

>  It may be that the situation becomes unfavourable to the quality of life of the species (or the population) due to raise in the number of individuals (overpopulation). 

Ecological crisis may be more or less brutal (occurring within a few months or taking as long as a few million years). They can also be of natural or anthropic origin. They may relate to one unique species or to many species (see the article on Extintion event).

Lastly, an ecological crisis may be local (as an oil spill) or global (a rise in the sea level due to global warming).

According to its degree of endemism, a local crisis will have more or less significant consequences, from the death of many individuals to the total extinction of a species. Whatever its origin, disappearance of one or several species often will involve a rupture in the food chain, further impacting the survival of other species.