The prefix = st1 /USgovernment has announced plans to list polar bears as a threatened species because of concerns that the ice where they live is melting. But as the BBC's Owen Clegg reports, theUSplans are also important for other reasons. It's estimated that there are no more than twenty-five thousand polar bears living in the wild, and this number could go down by a large amount as the floating ice upon which the bears survive melt away. Now, without admitting the cause of this melt, the US Fish and Wildlife Services are reviewing the bear's living conditions.    That action is being taken at all, and marks an important change for the Bush administration; for the first time, it may be forced to acknowledge a link between global warming and its effect on a species. Such a conclusion by an unwilling Bush administration could force far wider changes inWashington's policy towards the environment.    This review only came about after a union of environmental groups brought a legal case against the government to take action. Environmentalists, like David Doniger, believe that by calling on the protections of the Endangered Species Act, theUSgovernment may finally be forced to cut back on its sending out greenhouse gases:    "It is a very important thing today to have the Bush administration notice that global warming is threatening the existence of the polar bear. Now, it's up to the administration to do something to stop the global warming that's threatening the polar bear." ( David Doniger)    The United States is the world's largest emitter of greenhouse gases which are blamed for trapping heat from the sun and changing the earth's climate. Since taking office in 2001, President Bush has refused to make the link with global warming, but the bad, serious situation of the polar bear may force that position to change. Which country has been sending out the largest number of greenhouse gases according to the passage?
China. Britain. TheUnited States. Not mentioned.