The loss of biodiversity is a significant issue for scientists and policymakers and the topic is finding its way into living rooms and classrooms. Species are becoming extinct at the fastest rate known in geological history and most of these extinctions have been tied to human activity.
Major causes of biodiversity losses
- Habitat loss and destruction / Fragmentation, usually as a direct result of human activity and population growth, is a major force in the loss of species, populations, and ecosystems. For ex. Tropical rain forests which once covered around 14% of land surface now only cover around 6% of land area
- Alterations in ecosystem composition / Co-extinction, such as the loss or decline of a species, can lead to a loss of biodiversity. For example, efforts to eliminate coyotes in the canyons of southern California are linked to decreases in songbird populations in the area. As coyote populations were reduced, the populations of their prey, primarily raccoons, increased. Since raccoons eat bird eggs, fewer coyotes led to more raccoons eating more eggs, resulting in fewer songbirds.
- The introduction of exotic (non-native) species / Alien Species can disrupt entire ecosystems and impact populations of native plants or animals. These invaders can adversely affect native species by eating them, infecting them, competing with them, or mating with them. For ex. The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
- The over-exploitation (over-hunting, over-fishing, or over-collecting) of a species or population can lead to its demise.
- Human-generated pollution and contamination can affect all levels of biodiversity.
- Global climate change can alter environmental conditions. Species and populations may be lost if they are unable to adapt to new conditions or relocate.