VOA常速英语:Report: Ecosystems More Stressed Than Ever

Natural ecosystems in the United States are under greater stress from climate change than at any previous time in human history, according to a new report.

Experts from government agencies, academia and environmental organizations say these stressed ecosystems are also stressing wild plant and animal species, threatening the nation’s biodiversity.

When Super Storm Sandy ravaged the U.S. East Coast and inundated New York City in late October, many wondered if such extreme weather events might be linked to climate change, the gradual warming of the planet caused, in part, by decades of industrial emissions.

For New York governor Andrew Cuomo, there was no doubt.

“Climate change is a reality,” he said after Sandy struck.

Wreaking havoc

The same global reality that swamped New York City is also wreaking havoc on the nation’s wild places, according to a warning contained in the new report, "Impacts of Climate Change on Biodiversity, Ecosystems and Ecosystem Services."

Bruce Stein, a scientist with the National Wildlife Federation and a co-author of the report, says one of its key findings is that climate change is causing many plant and animal species to shift their geographic range and distribution faster than anticipated.

“What that means is that, as these species shift out of their historic ranges, we’re starting to see biological events happening earlier," Stein says. "We’re starting to see mismatches between things like flowers and their pollinators, and species that actually depend on one another.”

The impact of a warmer world isn’t just felt in more intense heat waves, droughts and storms every summer, but also in winters that are less cold.

“And those cold temperatures are a critical regulator of species outbreaks and also of species distributions," says ecologist Peter Groffman with the Cary Institute of Ecosystem Studies and also a co-author of the report. "And so what we’ve seen is that these pest outbreaks are much worse than they would be because we’ve lost these very cold temperatures.”

Assault on trees

Bug infestations are killing millions of trees in U.S. forests. If that assault continues, the report warns, tree mortality rates in western U.S. forests could double every 17 to 29 years. The loss of trees would lead to earlier melting of mountain snowpack and reduce the amount of water available for spring planting season.

“These changes in the winter affect ecosystems, biodiversity, during the summer period," Groffman says. "There are big changes in the timing of spring and fall, which affects the success for a variety of plant and animal species, and it affects the ability of ecosystems to hold on to improved water quality and air quality.”

That also means less water for people and communities to drink, says another report co-author, Mary Ruckelshaus, managing director of the Natural Capital Project.

“By most projections, climate change is going to triple the fraction of countries that are at high, or at very high, risk of running out of water," Ruckelshaus says. "People’s source of water is going to be increasingly imperiled due to climate change.”

High stakes

The report’s authors call for improved monitoring and better coordination among federal and state agencies to adapt to the impacts of climate change.  
    
Bruce Stein, with the National Wildlife Federation, says the need is urgent and the stakes are high.

“I think the bottom line is that these impacts are not just going to happen in 50 or 100 years, many of them already are here and are only projected to get worse over time," Stein says. "The good news though, is that climate adaptation finally is being taken seriously, and many state and federal land management agencies, as well as cities and towns, are beginning to put that in practice.”        

For example, according to Stein, efforts are being made to prevent a recurrence of what happened during Super storm Sandy: salty ocean water driven by the storm surge breached the freshwater marsh systems on the Atlantic coast, contaminating critical shore bird habitats.  

“Because just this type of breach was anticipated given rising sea levels, National Wildlife Federation and the State of Delaware are already working to create comparable marsh further inland and up slope that is better protected from heightened sea levels and storm surges," he says.   
 
The report released this week is one of several major technical studies being done as part of the U.S. National Climate Assessment, due out in 2013.