Maidenhair Trees (Ginkgo biloba) evolved hundreds of millions of years ago. They are the only remaining survivor of their ancient, and once abundant, plant family. They are now thought to be extinct in the wild, and the individuals that remain have all been planted -- they are now popular ornamental trees because of their resistance to pollution, drought, pests, and their ability to grow in a variety of soil conditions. Photo by Maya Walters. |
Biodiversity is
built over millions of years and extremely diverse habitats such as tropical rainforests have taken long stretches of geologic time to
develop. That's why the extinction of species is such an important issue: once they're gone, not only are they gone forever, but it takes
millions of years for new species to evolve in their place.
Some extinctions are natural, but a variety of human activities have vastly increased the numbers of species disappearing every day. Habitat destruction is the main cause, especially since the richest habitats with the most species, such as tropical forests, are being destroyed at the fastest pace. Extinction rates are now hundreds or even thousands of times higher than before humans came to be so numerous. Some scientists have estimated that as many as one fifth of all species alive today could be extinct or nearly extinct by the year 2020. |
loss of biodiversity -- page 1 of 5
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related topics
[biodiversity] [forests through time] [tropical forests] [forest life]
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