Endangered species
Endangered species
are living things threatened with
extinction
—that is, the dying off of all of their kind. Thousands of species of
animals and plants are endangered, and the number increases each
year. Some examples of endangered species are blue whales, giant
pandas, orangutans, rhinoceroses, sea turtles, snow leopards,
tigers, and whooping cranes. Among endangered plants are
running buffalo clover, Santa Cruz cypress, snakeroot, and many
species of cactuses.
Each species of plant and animal plays a part in the delicate
balance of its
ecosystem,
its relation to other living things and the environment. Thus, the
extinction of large numbers of species threatens the survival of
other living things, including human beings. As more species have
become endangered, ecosystems have become unstable or
collapsed. Fortunately, people have increased their efforts to
protect endangered species. See
Wildlife conservation
(Values of wildlife conservation)
.
Most biologists consider a species endangered if they expect it would die off completely in
less than 20 years if no special efforts were made to protect it, or if the rate of decline far
exceeds the rate of increase. Until the last few centuries, species became rare or died out as
a result of natural causes. These causes included changes in climate, catastrophic
movements in Earth's crust, and volcanic eruptions.
Today, species become endangered primarily because of human activities. Species mainly
become endangered because of (1) loss of habitat, (2) wildlife trade, (3) overhunting, and (4)
competition with domestic and nonnative animals.
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