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One consequence of the destruction of the environment by humans is the loss of biodiversity. Biodiversity is the variety of organisms in a geographic area. Biodiversity is an essential natural resource, because different organisms provide us with unlimited products including food, fibers for clothing, and medicines.
Biodiversity can also be thought of as the sum of all the genomes of all the organisms on Earth. Losing biodiversity means losing genes that might have been useful for things including nutrition and medicine.
Something we often overlook is that humans are part of the global ecosystem. When we destroy a species, the global ecosystem is affected, and ultimately humans will be affected too.
Human intervention represents three main threats to biodiversity. As we destroy the environment, we are also destroying the habitats of many organisms. These organisms must find a new place to live. Humans are overexploiting many species through excessive hunting and fishing. We are killing many species faster than they can replace themselves. Humans endanger native species by introducing foreign or exotic species that compete with native species.
The introduction of exotic species sometimes occurs by accident. South American fire ants entered the United States at Mobile, Alabama, as stowaways on cargo ships. The ants, which destroy other insects and some small animals, are now a problem in much of the south. Some exotic species, like starlings and bluebirds, are introduced on purpose. The exotic species sometimes out-compete the native species for food, causing the native species to die out. Exotic species may also prey on native species.
It isn't surprising that some ecosystems have more species than others. More than half the Earth's species are found in 17 regions, known to conservation biologists as "hot spots," covering only about 2% of land area. The regions with the greatest concentration of species are generally found in the tropics. Because these limited regions are home to so many species, they are very sensitive to habitat degradation. Destroying a small area can harm dramatic numbers of species all at once.
When studying species in trouble, conservation biologists classify them as threatened or endangered. An endangered species is in danger of extinction throughout most or all of the area it inhabits. A threatened species is likely to become endangered in the near future. In the United States, 735 species of plants and 496 species of animals are listed as threatened or endangered.
While many organizations are working to save threatened and endangered species, it isn't as simple as just increasing the number of organisms in a species. The total population of a species is usually composed of smaller populations. Some smaller populations are source populations, in which reproductive success exceeds mortality. Source populations increase the number of individuals. Other small populations are sink populations, in which mortality exceeds reproductive success. Sink population decrease the number of individuals.
To save a species, it's necessary to identify which populations are source populations, and find ways to help them expand. Conservation biologists are working to save threatened and endangered species around the world. But once a species becomes extinct, those organisms, and all the benefits they might've been able to provide to medicine and agriculture, are lost forever.
Copyright 2006 The Regents of the University of California and Monterey Institute for Technology and Education