The Evolution of Ecosystems

Predation

• When predation on a certain type of species within an area changes the population, the ecosystem has to evolve and change in order to thrive. For instance, in early prehistory, man might move into an area and hunt all the carnivores to near extinction. This allows the herbivore population in an area to flourish. In turn, this means more pressure placed on plant food sources. If the plant eaters in an area preferred trees and shrubs, the lack of control on their numbers could mean overeating and eventually the area shifting from a forest to a grassland. This in turn would attract new species of animals, while the old ones move elsewhere.

Introduced Species

• An ecosystem also evolves based on the introduction of a new species. This is something seen frequently in the lakes and rivers of the world, as fish are transported from all around the world every day. When foreign species of aquatic life are introduced into a body of water, sometimes the entire ecosystem has to evolve in order to accommodate the new life-form. This can be extremely disruptive to other species in the ecosystem. For instance, we have yet to see what the results will be of the introduction of the snakehead in various U.S. bodies of water.

Climate Change

• Climate change forces the balances in an ecosystem to evolve and change, as the suitability of an ecosystem for certain species shifts with the weather patterns. For instance, in a region where temperatures rise and water availability decreases, certain plants might no longer grow well. If those plants are a food source for a key species, that species migrates out of the region, leading to further ongoing changes. Climate change also forces physical reshaping of an ecosystem, such as when a drop off of precipitation causes small lakes or rivers to dry up.

Pollution

• Unfortunately, some ecosystems are forced to evolve and change much more quickly than they would due to the natural processes of the Earth, because of the pollutants man pours into the world. Air pollution, acid rain and -- perhaps more than anything else -- the pollution of water supplies create chain reactions in ecosystems that reshape them and cause consequences up to and including species extinctions.