单选题 Everybody knows that global fish stocks are heading for collapse. That is why governments try to limit the amount of fish taken out of the sea. But recent research suggests that the world is going about regulating fishing the wrong way—that fish stocks would fare better if efforts were made to protect entire ecosystems rather than individual species.
There are plenty of data to prove the importance of diversity on dry land. Until recently, however, there was little evidence that the same was the case in the oceans, which make up 90% of the biosphere, and on which a billion people rely for their livelihoods. In order to establish whether diversity matters in the sea as well as on land, 11 marine biologists, along with three economists, have spent the past three years crunching all the numbers they could lay their hands on. These ranged from the current United Nations Food and Agriculture Organisation"s database to information hundreds of years old, collected from kitchen records and archaeology. The results of their comprehensive analysis have been published in Science.
Marine biodiversity, they report, matters because it is variety per se that delivers services—such as maintaining water quality and processing nutrients—to humans as well as the goods people reap from the sea. It also ensures these goods and services recover relatively rapidly after an accident or natural disturbance. The new work is silent on exactly how biodiversity protects these things—merely showing that it does. Earlier work though has shown some possible mechanisms. One example from a study in Jamaica showed that continuously removing algae grazers from a reef allowed the algae to overwhelm the coral.
The latest study, led by Boris Worm of Dalhousie University, in Halifax, Canada, gathered the available material into four separate groups. The researchers found the same result from different pools of data, in different types of marine ecosystems and at different scales. The findings suggest that governments should rethink the way they try to manage fisheries. Marine reserves are common in the tropics, but policymakers in temperate countries tend to focus on one species at a time to control numbers of that species caught. They might do better to spend more time thinking about ecosystems and less bargaining over quotas.
Some governments claim to have already come around to the idea. In America, Britain and Canada officials are considering how to redraft fisheries policy. Scientists hope that the move will push the inevitably unhappy compromise between their recommendations and fishermen"s aspirations closer to their way.
Dr. Worm reckons that, the way things are going, commercial fish stocks will collapse completely by 2048. The date may be spuriously precise, but the danger is there. And so, if Dr. Worm is right, is a better way of making sure that it doesn"t happen.

单选题 The current efforts at protecting fish stocks are directed towards ______

单选题 On which of the following issues have scientists reached consensus?

单选题 The research done by the 11 marine biologists and three economists does not ______

单选题 Dr. Worm would advocate ______

单选题 The author"s attitude towards the prospect of protecting fish stocks is ______