氣候變遷擾亂了五大湖區國家公園

Five Great Lakes national parks and lakeshores are feeling the impacts of climate change, finds a new report by the Rocky Mountain Climate Organization and Natural Resources Defense Council. Lake Michigan may have some winters with no ice cover within 10 years, and Lake Superior may be ice-free in about three decades, the report warns.

The five largest parks on the Great Lakes are experiencing rising temperatures, decreased winter ice, eroding shorelines, spreading disease, and a crowding out of key wildlife and plant life.

"Human disruption of the climate is the greatest threat ever to America's national parks. This report details the particular threats that a changed climate poses to our Great Lakes national parks," said Stephen Saunders, president, Rocky Mountain Climate Organization and former deputy assistant secretary of the U.S. Department of the Interior overseeing the National Park Service.

The five parks are: Indiana Dunes National Lakeshore in Indiana near Chicago; Sleeping Bear Dunes National Lakeshore, Pictured Rocks National Lakeshore; Isle Royale National Park in Michigan, just offshore from Minnesota; and Apostle Islands National Lakeshore in Wisconsin.

The report documents that the amount of rain falling in heavy storms in the Midwest increased by 31 percent over the past century, a level well above the national average of 22 percent.

Winds over the Great Lakes are stronger than they used to be. Lake Superior wind speeds have increased by 12 percent since 1985.

The temperatures of Great Lakes waters are hotter, increasing more in recent decades than air temperatures have. Lake Superior's summer water temperatures rose about 4.5 degrees from 1979 to 2006, roughly double the rate at which summer air temperatures have gone up over the surrounding land.

In 2010, a tick of the type that carries Lyme disease was confirmed at Isle Royale for the first time - a fact stated publicly for the first time in this report. Cold temperatures previously prevented these ticks from reaching so far north, but their spread into the region had been projected as the climate gets hotter. The Lyme disease ticks also have spread to nearby Grand Portage National Monument for the first time.

The threats of climate disruption to the national parks in the Great Lakes are also threats to the Great Lakes regional economy, the report points out.

Mayor Larry J. MacDonald of Bayfield, Wisconsin said, "The City of Bayfield, as the gateway community to the Apostle Islands National Lakeshore, faces the financial reality that climate change will bring tremendous economic challenges to our National Lakeshore-based local tourism economy. We need to continue to respect and protect Lake Superior. When the Lake is healthy, our community and the Apostle Islands will continue to prosper."

The five parks featured in this report together drew more than four million visitors in 2010, according to the report. Visitor spending in 2009 totaled more than $200 million and supported nearly 3,000 jobs.

Said Thom Cmar, staff attorney in the Chicago office of the Natural Resources Defense Council, "We need to head off climate change quickly to protect our Great Lakes parks, the iconic landscapes and wildlife that live in them, and our own communities. Climate action is economic action in the Great Lakes."

"To protect the jobs and massive revenue that come out of these parks, Congress needs to either act on climate or get out of the way and let the EPA do its job to limit carbon pollution," Cmar said.

The report, "Great Lakes National Parks in Peril: The Threats of Climate Disruption," finds higher temperatures, less winter ice, shoreline erosion, and loss of wildlife.

In Isle Royale, the moose population has declined, as have the numbers of the wolves that depend on them as prey. The moose population is down to about 515, half the park's long-term average.

Temperatures higher than moose can tolerate could be responsible, as in nearby northwest Minnesota, where the moose population has crashed in the past two decades from 4,000 to fewer than 100 animals, coinciding with higher temperatures.

Also, warmer winters in Isle Royale enable enough ticks to overwinter and cause such a large loss of blood among the moose that they are more vulnerable to the park's wolves, the report explains.

Isle Royale's wolf population has fallen, too. The park's moose make up 90 percent of the wolves's prey, and declines in the moose population threaten the wolves. The park now has only 16 wolves in two packs, compared to 24 wolves in four packs a few years ago.

Lynx and martens in Isle Royale also at risk as the climate changes.

Birds at risk of being eliminated from the parks include common loons and ruffed grouse, iconic birds of the Great Lakes and the North Woods.

Other birds are also at risk. Botulism outbreaks linked to high water temperatures and low lake levels now kill hundreds to thousands of birds a year in Sleeping Bear Dunes National Lakeshore. So many dead birds drop onto the park's beaches that the National Park Service patrols from June through November to clean up the bird carcasses.

"Change in nature is natural. But the changes we face with the accelerated rate of global climate change that our human activities have caused don't allow millennia or even centuries for adaption; the changes now will take place in only decades without time for nature to adapt," warned Dale Engquist, former superintendent, Indiana Dunes National Lakeshore, and president, Chicago Wilderness Trust.