第1个回答 2010-12-23
According to scientists, more than one and one-half million species exist on the earth today. However, recent estimates state that at least 20 times that many species inhabit the planet.
In the United States, 735 species of plants and 496 species of animals are listed as threatened or endangered.
266 of these listed species have recovery plans currently under development.
There are more than 1,000 animal species endangered worldwide.
There are more than 3,500 protected areas in existence worldwide. These areas include parks, wildlife refuges and other reserves. They cover a total of nearly 2 million square miles (5 million square km), or 3% of our total land area.
Aquatic species, which are often overlooked, are facing serious trouble. One third of the United States‘s fish species, two-thirds of its crayfish species, and almost three-quarters of its mussel species are in trouble.本回答被提问者采纳