BOULDER, Colo., May 17 (UPI) -- One of the advantages of being the world's only superpower is it seems to bestow a relative immunity to the prospective ravages of global warming.
Or does it?
The Pew Center of Global Climate Change's report, "A Synthesis of Potential Climate Impacts on the United States," finds the country as whole has a high capacity to adapt to anticipated climate change, although the effects to natural systems, different economic sectors and different regions will vary.
This could be viewed as another case of the rich getting richer, because the study also says the impacts of climate change on poorer developing countries "are likely to be negative, even at lower levels of warming."
These conclusions should come as no surprise to anyone who has followed the climate change debate. Take, for example, the U.N. Intergovernmental Panel on Climate Change's "Summary for Policymakers."
"Overall, climate change is projected to increase threats to human health, particularly in lower income populations, predominantly within tropical/subtropical countries," the document said.
The projected effects of climate change on the U.S. economy vary, depending upon the source of the estimate. The Pew study predicts low-to-moderate warming will cost about 1 percent of the gross domestic product.
Margo Thorning, managing director for the International Council for Capital Formation, said trying to reduce U.S. greenhouse gas emissions to levels set by the Kyoto protocol would cost between 1 percent and 4.2 percent of GDP.
Because the cost of moderate warming is only 1 percent, this would appear to be a strong argument for doing little to stem greenhouse gases.
Most of the anthropogenic greenhouse gases -- those generated by human activity -- result from the burning of fossil fuels.
"The only way to achieve a big absolute reduction in emissions is through a substantial reduction in economic activity," William O'Keefe, president of the George C. Marshall Institute in Washington, D.C., said in a speech in June 2003.
"That simply is not politically realistic nor desirable for growing populations seeking to increase their standards of living," he added. "It is not possible to achieve desired levels of economic growth and simultaneously use less energy."
Perhaps, but as the world's largest producer of greenhouse gases, the response of the world's only superpower to this issue is going to say a lot to the world about how we put that power to use.
Like most assessments of the costs of environmental controls, none of these analyses of the costs of carbon restrictions takes a concomitant look at what benefits might be derived. A study by Princeton University's Woodrow Wilson School of Public and International Affairs looked at most of the projections of the costs of environmental regulation since the 1970s. Researchers found all of the estimates included only the costs of regulation -- not the benefits.
One of the benefits of slowing global climate change that is difficult to quantify is the impact on the natural world and the biodiversity in it. A lot of these components -- free-ranging wildlife, water to irrigate the golf course, coral reefs to explore while snorkeling -- might indeed be things we could get along without, but they also represent things that make life varied and interesting. Placing a price on them has always presented a challenge to economists.
"Natural ecosystems appear to be quite vulnerable to climate change," the Pew report said. "Climate change threatens to result in the loss of many coral reefs, coastal wetlands, endangered species (particularly those with limited range and mobility), cool- and cold-water fish, and boreal and alpine forest species."
Between 15 percent and 37 percent of species sampled in six critical world ecological regions could become extinct by the year 2050 because of their inability to adapt to the changing climate, according to a study sponsored by IUCN -- The World Conservation Union.
"Climate change could rival habitat loss and other major threats to land animals and plants," the study found.
The condition of U.S. plants, animals and fish already is perilous, before climate change is taken into account. The H. John Heinz III Center for Science, Economics and the Environment surveyed the "State of the Nation's Ecosystems" at the end of 2003. Researchers found 19 percent of native animal species and 15 percent of native plant species are "imperiled" or "critically imperiled." Another 4 percent of animals and 1 percent of plants are extinct.
If you include other species that are listed as "vulnerable," fully one-third of all U.S. plant and animal species are at risk of population losses or extinction.
So, although the U.S. economy may hold up nicely under warming scenarios, how do these non-economic units respond?
A few researchers say fears of ecosystem failures from climate change are exaggerated. Sherwood Idso and other authors, also writing for the Marshall Institute, argue essentially that increases in CO2 will enhance plant growth, leaving many species better off than before.
This view is a minority one among biologists, however. Even enhanced plant productivity, which is likely to be a result of greenhouse warming, is not an undiluted benefit. Ecosystems that plants support are not simply about carbon intake and size. Not only do plants need other nutrients, so do the animals that feed on plants.
As anthropogenic CO2 in the atmosphere increases, it gives plants more carbon fertilizer, but the relative amount of nitrogen -- an equally or more essential nutrient for plant herbivores -- in the plant goes down.
According to Mark Hunter, director of the Center for Biodiversity at the University of Georgia, "All this new growth on the plants sucks, as far as the herbivores are concerned."
The signals are unambiguous that the biosphere already is responding to climate change. Plant ecologist Nina Leopold Bradley maintains a record that goes back nearly 70 years of the seasonal behavior of 300 species in Wisconsin. About half of the species Bradley tracks are exhibiting earlier springtime behavior -- plants blossoming earlier, birds migrating sooner, and so on -- as a result of warmer temperatures.
Camille Parmesan, a biology professor at the University of Texas in Austin, has looked at the impact of this early spring arrival on butterflies. In California, she tracked checkerspot butterflies and found populations of the insects became extinct in areas where they previously had thrived and healthy populations were found considerably north of earlier ones.
Parmesan also studied populations of about 35 different species of butterflies in Europe. She and her co-authors reported in the British journal Nature that of the 35 non-migratory species of European butterflies, 63 percent shifted their ranges north by between 20 and 140 miles. Only 3 percent shifted southward.
There are many other examples of animals, plants, insects and corals responding to climate change. Some of the changes have resulted in healthier populations, but most appear to be threatened with declining populations, habitat availability, food sources or some combination of threats.
The Pew report echoes the scientific majority, at least, when it concludes, "Biodiversity in the United States is likely to be reduced by climate change."
Dan Whipple covers the environment for UPI Science News. E-mail firstname.lastname@example.org
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