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natural habitats. They clear
trees from forests to build
houses, farms, cities, and roads. One of the most
terrible instances of habitat destructions is the cutting
down of the
tropical rainforests. It is estimated that
these rainforests, which cover less than 10
percent of
the Earth, contain almost half of all the world’s plant
and animal species.
Human activity has had a devastating effect on the natural environment.
Each year, an international organization of scientists releases a special “red list”
that updates the
status of more than 44,000 animal and plant species. In 2008,
the organization reported that 25 percent of our planet’s 5,487 mammals are on
the
verge of extinction. It also claimed that almost 40
percent of all species are
“threatened” with extinction, including 33 percent of all
amphibians, a quarter of
the Earth’s
coniferous trees, and about 12 percent of all birds. Of all threatened
species
on the red list, about 3,000 are “critically endangered,” which means
they could disappear soon.
What would happen to people if the “Sixth Extinction” takes place? Scientists
say life on Earth would be grim. There would
not be enough food to eat, and water
would be too polluted to drink. New species of pests and plants would invade the
natural areas that remain. These invaders could carry new kinds of germs,
causing
diseases that human bodies cannot resist. Without plants to help cool the sun, the
ice at the North and South Poles could melt, causing sea levels to rise and wash
away coastal cities.
By wiping out other species, human beings might be paving
the way for the greatest extinction of all: their own.
Reading Time
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547 words
30
tropical --- relating to warm climates
36
status --- state
or condition
38
verge --- brink or threshold
39
amphibian --- an animal with characteristics of fish and reptiles
40
coniferous --- cone-bearing
