Port Lympne Reserve, which runs a breeding(繁育) programme, has welcomed the arrival of a rare black rhino calf (犀牛幼崽）. When the tiny creature arrived on January 31. she became the 40th black rhino to be born at the reserve. And officials at Port Lympne were delighted with the new arrival, especially as black rhinos are known for being difficult to breed in captivity(圈养).
Paul Beer, head of rhino section at Port Lympne, said:" Obviously we're all absolutely delighted to welcome another calf to our black rhino family. She's healthy, strong and already eager to play and explore. Her mother, Solio, is a first-time mum and she is doing a fantastic job. It's still a little too cold for them to go out into the open, but as soon as the weather warms up, I have no doubt that the little one will be out and about exploring and playing every day. "
The adorable female calf is the second black rhino born this year at the reserve, but it is too early to tell if the calves will make good candidates to be returned to protected areas of the wild. The first rhino to be born at Port Lympne arrived on January 5 to first-time mother Kisima and weighed about 32kg. His mother, grandmother and great grandmother were all born at the reserve and still live there.
According to the World Wildlife Fund, the global black rhino population has dropped as low as 5500, giving the rhinos a "critically endangered" status.
When you were trying to figure out what to buy for the environmentalist on your holiday list, fur probably didn't cross your mind. But some ecologists and fashion(时装)enthusiasts are trying to bring back the market for fur made from nutria(海狸鼠).
Unusual fashion shows in New Orleans and Brooklyn have showcased nutria fur made into clothes in different styles. "It sounds crazy to talk about guilt-free fur—unless you understand that the nutria are destroying vast wetlands every year," says Cree McCree, project director of Righteous Fur.
Scientists in Louisiana were so concerned that they decided to pay hunters $5 a tail. Some of the fur ends up in the fashion shows like the one in Brooklyn last month.
Nutria were brought there from Argentina by fur farmers and let go into the wild. "The ecosystem down there can't handle this non-native species(物种). It's destroying the environment. It's them or us," says Michael Massimi, an expert in this field.
The fur trade kept nutria in check for decades, but when the market for nutria collapsed in the late 1980s, the cat-sized animals multiplied like crazy.
Biologist Edmond Mouton runs the nutria control program for Louisiana. He says it's not easy to convince people that nutria fur is green, but he has no doubt about it. Hunters bring in more than 300,000 nutria tails a year, so part of Mouton's job these days is trying to promote fur.
Then there's Righteous Fur and its unusual fashions. Model Paige Morgan says, "To give people a guilt-free option that they can wear without someone throwing paint on them—I think that's going to be a massive thing, at least here in New York. "Designer Jennifer Anderson admits it took her a while to come around to the opinion that using nutria fur for her creations is morally acceptable. She's trying to come up with a label to attach to nutria fashions to show it is eco-friendly.
How does an ecosystem(生态系统) work? What makes the populations of different species the way they are? Why are there so many flies and so few wolves? To find an answer, scientists have built mathematical models of food webs, noting who eats whom and how much each one eats.
With such models, scientists have found out some key principles operating in food webs. Most food webs, for instance, consist of many weak links rather than a few strong ones. When a predator(掠食动物) always eats huge numbers of a single prey(猎物), the two species are strongly linked; when a predator lives on various species, they are weakly linked. Food webs may be dominated by many weak links because that arrangement is more stable over the long term. If a predator can eat several species, it can survive the extinction(灭绝)of one of them. And if a predator can move on to another species that is easier to find when a prey species becomes rare, the switch allows the original prey to recover. The weak links may thus keep species from driving one another to extinction.
Mathematical models have also revealed that food webs may be unstable, where small changes of top predators can lead to big effects throughout entire ecosystems. In the 1960s, scientists proposed that predators at the top of a food web had a surprising amount of control over the size of populations of other species—including species they did not directly attack.
And unplanned human activities have proved the idea of top-down control by top predators to be true. In the ocean, we fished for top predators such as cod on an industrial scale, while on land, we killed off large predators such as wolves. These actions have greatly affected the ecological balance.
Scientists have built an early-warning system based on mathematical models. Ideally, the system would tell us when to adapt human activities that are pushing an ecosystem toward a breakdown or would even allow us to pull an ecosystem back from the borderline. Prevention is key, scientists say, because once ecosystems pass their tipping point(临界点), it is remarkably difficult for them to return.
