124 Nature
Endangered Species
All over the world, plant and animal species are now at risk
of. EXTINCTION because of changes humans are causing
to the environment. Experts estimate that up to 30,000 of
these endangered species may now be dying out each year
- including many that have not yet been identified.
FIND OUT MORE. Dinosaurs 78–79 • Evolution 74–75 • Habitats 82–84 • Human Impact 64–65
WHAT IS THE WORST PROBLEM FACING WILDLIFE?
The greatest single threat to the world’s wildlife is
habitat loss – destruction of the wild places where
animals live. In many regions, forests are felled,
marshes drained, and grasslands cleared to build roads,
towns, mines, and dams. Pollution from towns, farms,
and factories also poisons wildlife on land and at sea.WHY ARE ISLAND SPECIES ESPECIALLY AT RISK?
Island species are at greater risk than most because
many are found nowhere else. Their populations are
often very small, so they are more easily affected by
new threats. Many island animals are not used to
predators. When new creatures such as cats or rats are
brought to islands, they can devastate wildlife.WHAT ARE MASS EXTINCTIONS?
Mass extinctions occur when large numbers of
species die out at once due to rapid changes in the
environment. Around 65 million years ago, a mass
extinction wiped out the dinosaurs. Now experts fear
that humans are causing a new wave of extinctions.HOW DO INTRODUCED SPECIES THREATEN WILDLIFE?
When new animals are brought into an area they can
sometimes take over habitats. If they are stronger or
breed faster than local species, they may out-compete
them for food. New predators often multiply rapidly
and start killing local wildlife. Creatures that cannot
escape, such as flightless birds, are
especially at risk.BURNING IVORY 3
These elephant tusks were confiscated from
poachers and are being destroyed so they cannot
be sold. Although elephants are protected by law,
there is a large illegal market for ivory, so
elephants remain in constant danger.EXTINCTION
Extinction occurs when all the members
of a species die out. Extinction is a natural
process that has happened throughout the
3.5 billion years that life has existed on
our planet – but now many creatures aredying out at once because of humans.
1 SPOTTED OWL
Spotted owls are at risk because
the North American forests where
they live are being cut down.
Tropical rainforests hold a huge
variety of plants and animals, but
these are also disappearing fast.4 DEAD AS A DODO
Dodos were large flightless birds that once lived on
islands in the Indian Ocean. They became extinct
by 1800 because sailors hunted them for food.Each tusk is made
of ivory worth
thousands of
dollars on the
black marketendangered
species