Chapter 4 Chapter Summary

  The major threats to biodiversity are habitat destruction, fragmentation, degradation (which includes pollution), climate change, overexploitation, invasive species, and disease. All of these threats result from the use of the world’s natural resources by an increasing human population.

  Habitat destruction particularly threatens rain forests, wetlands, coral reefs, and other species-rich communities.

  Habitat fragmentation is the process whereby a large, continuous area of habitat is both reduced and divided into two or more fragments. Habitat fragmentation can lead to the rapid loss of some of the remaining species because it creates barriers to the normal processes of dispersal, colonization, and foraging. Particular fragments may contain altered environmental conditions that make them less suitable for the original species.

  Environmental pollution eliminates many species from ecosystems even where the structure of the community is not obviously disturbed. Environmental pollution results in pesticide biomagnification; contamination of water with industrial wastes, sewage, and fertilizers; and air pollution resulting in acid rain, excess nitrogen deposition, photochemical smog, and high ozone levels.