MadagascarThere are at least 8 million unique species of life on the planet, if net far more, and you could be forgiven for believing that all of them can be found in Andasibe. Walking through this rain forest in Madagascar is like stepping into the library of life. Sunlight seeps through the silky fringes of the Ravenea louvelii, an endangered palm (棕榈树) found, like so much else on this African island, nowhere else.
Madagascar which separated from India 80 million to 100 million years ago before eventually settling off the southeastern coast of Africa, is in many ways an Earth apart. All that time in geographic isolation made Madagascar a Darwinian playground, its animals and plants evolving into forms utterly original. Some 90% of the island's plants and about 70% of its animals arc endemic, meaning that they arc found only in Madagascar. But what makes life on the island unique also makes it uniquely vuhnerable, which means if we lose these animals on Madagascar, they're gone forever.
That loss seems likelier than ever because the animals are under threat as never before. Once lushly forested, Madagascar has seen more than 80% of its original vegetation cut down or burned since humans arrived at least 1500 years ago, fragmenting habitats and leaving animals effectively homeless. Unchecked hunting wiped out a number of large species, and today mining, logging and energy exploration threaten those that remain. It has an area the size of New Jersey in Madagascar that is still under forest, and all this incredible diversity is crammed into it.
Madagascar is a conservation hot spot a term for a region that is very biodiverse and particularly threatened--and while that makes the island special, it is hardly alone. Conservationists estimate that extinctions worldwide are occurring at a pace that is up to 1 000 times as great as history's background rate before human beings began scattering. Worse, that die-off could be accelerating.
Price of Extinction
There have been five extinction waves in the planet's history—including the Permian (二叠纪的) extinction 250 million years ago, when an estimated 70% of all terrestrial animals and 96 % of all marine creatures vanished, and, most recently, the Cretaceous (白垩纪的) event 65 million ),ears ago, which ended the reign of the dinosaurs. Though scientists have directly assessed the viability of fewer than 3% of the world's described species, the sample polling of animal populations so far suggests that we may have entered what will be the planet's sixth great extinction wave. And this time the cause isn't an unsteady planet or volcanoes. It's us.
Through our growing numbers, our thirst for natural resources and, most of all, climate change-- which, by one reckoning, could help carry off 20% to 30% of all species before the end of the century-- we're shaping an Earth that will be biologically exhausted. A 2008 assessment by the: International Union for Conservation of Nature found that nearly 1 in 4 mammals worldwide were at risk for extinction, including endangered species. Over fishing and acidification of the oceans are threatening marine species as diverse as the corals.
Scary for conservationists, yes. but the question arises: Why should it matter to the rest of us? After all, nearly all the species that were ever alive in the past are gone today. Evolution demands extinction. When we're using the term extinction to talk about the fate of the US auto industry, does it really matter if we lose species like the Yangtze River dolphin and the golden toad, all of which have effectively disappeared in recent years? What docs the loss of a few species among millions matter?
For one thing, we're animals too, dependent on this planet like every other form. of life. The more species living in an ecosystem, the healthier and more productive it is, which matters for us--a recent study by the World Wildlife Fund (WWF) e
A．At least 8 million unique species of life.
B．More than 8 million unique species of life.
C．A library of life
