|THE EXTINCTION CRISIS
The human species, one of millions of life forms on this planet, is threatening the very existence of many other species. Biological diversity, or biodiversity, is the variety of life forms that interact tosupport and sustain the balance of nature.
As the human population grows, more and more of the Earth's living space, food, and other resources are consumed. Explosive human population growth and consumption are causing loss of biological diversity at an ever-increasing pace, an extinction crisis that threatens to surpass the mass extinctions that have occurred periodically during the Earth's history.
Never before have so many species been threatened with extinction in so short a period of time. In fact, some scientists estimate that species are disappearing at the rate of one every day, hundreds of times faster than the background rate of extinction. (See discussion of extinction rates in "IN THE WILD: Extinct".)
What else is different about this mass extinction, in addition to how fast it is happening? Scientists believe that other extinction events were caused by phenomena such as climate change and collisions of asteroids or meteors with the Earth. After these events, new species evolved that were adapted to the changed conditions.
In contrast, modern extinctions are being caused by human use of the Earth's resources.
If humans continue to destroy, degrade, and fragment the habitat that for millions of years has supported other life forms, it will be difficult for new species to evolve. Only species that are adapted to human-altered landscapes will be able to survive or evolve.
Note: Emphasized words can be found in the glossary.