Environmental Engineering Reference
In-Depth Information
urge us to listen more carefully to what birds are
telling us about the state of the environment for them
and for us.
Science: Deliberately Introduced Species
Many nonnative species provide us with food,
medicine, and other benefits. A few wipe out some
native species, disrupt ecosystems, and cause large
economic losses.
We depend heavily on nonnative organisms for ecosys-
tem services, food, shelter, medicine, and aesthetic en-
joyment. According to a 2000 study by ecologist David
Pimentel, introduced species such as corn, wheat, rice,
other food crops, cattle, poultry, and other livestock
provide more than 98% of the U.S. food supply. Simi-
larly, nonnative tree species are grown in about 85% of
the world's tree plantations. Some deliberately intro-
duced species have also helped control pests.
The problem is that some introduced species have
no natural predators, competitors, parasites, or patho-
gens to help control their numbers in their new habi-
tats. Such species can reduce or wipe out populations of
many native species and trigger ecological disruptions.
Figure 9-11 shows some of the estimated 50,000 nonna-
tive species that, after being deliberately or accidentally
Figure 9-9
Threatened natural capital on an island:
endangered ring-tailed lemur in Madagascar, a threatened
island jewel of biodiversity in the Indian Ocean off the coast
of Africa. Half of the island's lemur species are endangered.
Madagascar's plant and animal species are among the world's
most endangered, mostly because of loss of habitat from slash-
and-burn agriculture on poor soils, fueled by rapid population
growth.
Cerulean warbler
Sprague's pipit
Bichnell's thrush
Black-capped vireo
Golden-cheeked warbler
Florida scrub jay
California gnatcatcher
Kirtland's warbler
Henslow's sparrow
Bachman's warbler
Figure 9-10
Threatened natural capital:
the 10 most threatened species of U.S. songbirds according to a
2002 study by the National Audubon Society. Most of these species are vulnerable because of habitat loss and
fragmentation from human activities. Almost 1,200 species—12% of the world's 9,800 known bird species—
may face premature extinction from human activities during this century. (Data from National Audubon Society)
