野性南美洲(一)

Bbc系列之《野性南美洲》文本

野性南美洲（一）

South America is a continent of extremes . It has the world's longest mountain range... the Andes. In Amazonia, it has the mightiest riverand the greatest expanse of rainforest on the planet. And the driest desert on earth the Atacama, lies beside one of the world's richest seas. South America also contains incredible variety. Almost no other continent can boast such a wealth of wildlife living in such a range of different landscapes. Almost everywhere you go there's an extraordinary diversity of life. But how did all these unique worlds come about? To understand the natural history of South America we must go back in time back to the age of the dinosaurs. South America was then part of Gondwana a massive continent that also included what are now Africa Australia, India and Antarctica. This was a world dominated by reptiles. Descendants of those ancient creatures still live in South America today. And the forests of southern Chile still have plants that the dinosaurs would have recognized tree ferns and the bizarre monkey puzzle tree. Then, a new group of animals appeared animals like this. The early mammals were small and many were marsupials like this shrew opossum. It lives in the cold damp forests of southern Chile where it hunts for insects and earthworms. The shrew opossum shares these ancient forests with this other small marsupial. Local people call it the 'monito del monte' or 'monkey of the mountains'. It's so tiny you could hold it in the palm of your hand. It too eats insects but also has a taste for fruit. When we think of mammals with a pouch it's perhaps Australia with its kangaroos that comes to mind. But South America also has over eighty species of marsupial a legacy of the time when the two continents were joined together. Around a hundred million years ago the giant continent of Gondwana slowly

split apart. South America became an enormous island cut off from the rest of the world..The next chapter in South America's history was violent and prolonged. It changed the face of the continent for ever. Starting some eighty million years ago the island was convulsed by a series of massive volcanic eruptions that continue today. Forced up by movements

deep in the earth's crust a huge chain of mountains arose spanning the length of the continent The Andes. Running over five thousand miles this is the longest mountain chain on earth. At its northern end tropical cloudforest covers the slopes yet its peaks are so high that even on the equator they carry permanent snow and ice. In the central Andes there's a high dry desert the altiplano. As you travel further south the mountains are lower but they're that much closer to the Antarctic. In the far south the Patagonian ice sheets are the largest expanse of ice outside the polar regions. They cover more than seven thousand square miles and their glaciers flow all the way to the sea. But even here in the shadow of the ice animals survive. In the shadow of the Patagonian icecap animals must survive ferocious winds and winters of heavy snow. Only the hardiest animals can live here like guanacos South American relatives of the camel and foxes. Even for them surviving the winter is a challenge Patagonia may be severe but it's not the most extreme part

of the Andes. That's back in the heart of the range an oxygen-starved plateau more than four thousand metres high. Here, in the Altiplano meltwater from the surrounding peaks evaporates in huge salt lakes. Frozen by night and baked by day these caustic saltflats must be one of the most inhospitable places on earth. This is Salar Uyuni in the Bolivian Andes. Covering four and a half thousand square miles it's the largest expanse of salt on the planet. Incredibly, islands in this sea of

salt actually support life. Viscachas. These rabbit-sized rodents have to contend with thin air, bitter cold, and an almost total lack of water. They get just enough moisture to