Christine J.

A keystone species is a species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass. Given this definition, as predators and modifiers of the ecosystem, humans can be considered a keystone species. The extinction of the human species would have a significant impact on the environment, although this impact would most likely be more positive than negative over time. Humans have such a destructive impact when compared to our total mass on this earth. If humans ceased to exist, deforestation would decrease, pollution in fresh waterways would begin to clear up and the population size of endangered species may increase. The extinction of us would also most likely result in the extinction of many pathogens that rely on humans as a host, furthering the point that humans are a keystone species.