Environmental Engineering Reference
In-Depth Information
Indian Tiger
Black Rhino
Range 100 years ago
Range today
(about 2,300 left)
Range in 1700
Range today
(about 2,400 left)
African Elephant
Asian or Indian Elephant
Former range
Probable range 1600
Range today
Range today
(34,000-54,000 left)
Active Figure 9-8 Natural capital degradation: reductions in the ranges of four wildlife species, mostly as
the result of habitat loss and hunting. What will happen to these and millions of other species when the world's
human population doubles and per capita resource consumption rises sharply in the next few decades? See
an animation based on this figure and take a short quiz on the concept. (Data from International Union for the
Conservation of Nature and World Wildlife Fund)
mostly because of habitat loss and fragmentation. A
2002 National Audubon Society study found that one-
fourth of all U.S. bird species are declining in numbers
or are at risk of disappearing. Figure 9-10 (p. 192) shows
the 10 most threatened U.S. songbird species.
Conservation biologists view this decline of bird
species with alarm. Why? Birds are excellent environ-
mental indicators because they live in every climate and
biome, respond quickly to environmental changes in
their habitats, and are easy to track and count.
In addition, birds play important ecological roles.
They help control populations of rodents and insects
(which decimate many tree species), pollinate a vari-
ety of flowering plants, spread plants throughout
their habitats by consuming and excreting plant seeds,
and scavenge dead animals. Conservation biologists
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