单项选择题

Unchecked climate change could force up to 72 percent of bird species in some areas into extinction, but the world still has a chance to limit the losses, conservation group World Wildlife Fund (WWF) said in a report on Tuesday.
From migratory insect-eaters to tropical honeycreepers (蜜旋木雀) and cold water penguins, birds are highly sensitive to changing weather conditions and many are already being affected badly by global warming, the new study said.
"Birds now indicate that globa1 warming has set in motion a powerful chain of effects in ecosystems worldwide," WWF said. "Robust evidence demonstrates that climate change is affecting birds’ behavior--with some migratory birds even failing to migrate at all."
In the future, it said, unchecked warming could put large numbers of species at risk, with estimates of extinction rates as high as 72 percent, "depending on the region, climate scenario and potential for birds to shift to new habitats".
It said the "more extreme scenarios" of extincitons could be prevented if tough climate protection targets were enforced and greenhouse gas emissions cut to keep global warming increases to less than 2 degrees Celsius above pre-industrial levels.
Already in decline in Europe and the United States, many migratory birds were now missing out on vital food stocks that are appearing earlier and earlier due to global warming, widely blamed by scientists on emissions from burning fossil fuels.
In Canada’s northern Hudson Bay, the report said, mosquitoes were hatching and reaching peak numbers earlier in the spring, but seabirds breeding there had not adjusted their behavior. In the Netherlands, it added, a similar mismatch had led to the decline of up to 90 percent in some populations of pied flycatchers over the last two decades.
Predicted rising temperatures could see Europe’s Mediterranean coastal wetlands--critical habitats for migratory birds--completely destroyed by the 2080s, it said. Rising temperatures were also seen having disastrous impacts on non-migratory species, as their habitat ranges shifted.
"Many centers of species richness for birds are currently located in protected areas, from which birds may be forced by climatic changes into unprotected zones," the report said.
In the U.S., unabated wanning was seen cutting bird species by nearly a third in the eastern Midwest and Great Lakes, while almost three-quarters of rainforest birds in Australia’s northeastern Wet Tropics were at risk of being wiped out. In Europe, the endangered Spanish imperial eagle, currently found mainly in natural reserves and parks, is expected to lose its entire current range. Also at high risk were eight species of brightly colored Hawaiian honeycreeper, Galapagos Islands penguins and the Scottish capercaillie--the world’s biggest grouse--which WWF said could lose 99 percent of its habitat due to warming.
One example of bird extinctions caused by global warming is that ______.