Global Warming Could Threaten Human, Ecosystem Health

By Cat Lazaroff

WASHINGTON, DC, December 13, 2000 (ENS) - The climate changes associated with global warming are likely to be hardest on the elderly, the infirm and the poor, particularly in developing countries, shows a new report by the Pew Center on Global Climate Change. The study finds that the United States may have sufficient resources to prevent the worst possibilities - but warns that poorer countries may not fare as well.

A second study, also released by the Pew Center, finds that global climate change will cause major changes in natural ecosystems - and the plants and animal communities that make up these ecosystems - across the United States. The Pew Center is a nonprofit group created in 1998 by the Pew Charitable Trusts, one of the United States' largest philanthropies.


Climate change - largely caused by greenhouse gas emissions from human sources - raises the possibility that elevated temperatures, air contaminants and changes in precipitation patterns could pose increased health risks.


Diseases that are carried by mosquitoes, like malaria and West Nile Virus, are likely to spread into new territory as the climate warms (Photo courtesy Centers for Disease Control and Prevention)
Public health experts Dr. John Balbus of The George Washington University and Dr. Mark Wilson of The University of Michigan sifted through the evidence of climate related health risks.

The researchers found that if climate change results in more heat waves and air pollution episodes, certain populations are likely to suffer more than others, particularly the elderly, the infirm, and the poor.

While there are indications that a global warming trend may increase the risks of certain water borne and animal carried diseases, sanitation and public health systems in the U.S. are generally sufficient to prevent these diseases from dramatically increasing in incidence or distribution, the study found. However, many developing countries lack the resources and public health systems needed to prevent such outbreaks.

The report says government officials around the world need to maintain and strengthen public health systems. The researchers recommend that health officials increase their surveillance for potential disease outbreaks, and improve hygiene, water quality and control of animal disease carriers like mosquitoes and rats.

The links between climate and human health are complex and not fully understood. But the researchers warn that uncertainty about adverse health effects should not be interpreted as certainty of no adverse health effects.


Warmer weather could bring back the days of dangerously polluted air, like this pall of smog hanging over Los Angeles, California in 1972 (Photo by Gene Daniels, courtesy EPA)
The potential for unexpected events - such as sudden changes in climate or the emergence of new diseases - cannot be ruled out, the report says.

"There have been a lot of claims and counter claims about the potential human health impacts of global climate change," said Pew Center president Eileen Claussen. "An honest assessment must acknowledge that the United States can probably avoid the worst scenarios of disease outbreaks from climate related causes."

"At the same time, we should pay more attention to the climate related health risks faced by people in less developed countries, and by the most vulnerable people in our own country," Claussen said. "And we need to beef up health surveillance systems to guard against the possible emergence of unexpected health threats."


The Pew Center commissioned two ecologists, Dr. Jay Malcolm of the University of Toronto and Dr. Louis Pitelka of the University of Maryland Center for Environmental Science, to review evidence of potential ecosystem effects of global warming.


As the climate warms, eastern woodlands like these that produce spectacular fall foliage may become a thing of the past (Photo courtesy
Their report describes the "very real possibility" that global warming will disrupt the integrity of many of the land based ecosystems on which humans depend. Ecosystems provide humans such valuable goods and services as foods, raw materials, recreational opportunities, clean air and water, and erosion control.

The importance of ecosystems extends beyond economics and tangible benefits, with many people placing a high value on the spiritual and aesthetic role nature plays in their lives, the report notes. Despite the crucial roles of terrestrial ecosystems, they are increasingly threatened by the impacts of a growing human population, through habitat destruction and air and water pollution, and now as a result of global climate change.

"This report describes how climate change is likely to profoundly alter the natural environment," said Pew Center president Claussen. "It underscores the point that domestic and international action to deal with climate change is needed sooner rather than later."

As the earth warms, the distribution of land based ecosystems will change as plants and animals follow the shifting climate, the researchers found. For example, the eastern United States will likely lose many of its oak and maple forests as climate zones shift northward.

Sugar maples, so much a part of northeastern states such as Vermont, are likely to be replaced by oaks, the study notes. Some habitats - such as those found in the high elevations in mountainous regions of the West - are likely to shrink in a warming world.

native plants

Warmer temperatures could let prairie plants expand into areas now dominated by forests (Photo courtesy University of Minnesota)
Both the amount and rate of anticipated warming pose threats to the nation's biological diversity, the report found. The rate of anticipated climate change is estimated to be ten times that seen in the last Ice Age. As a result, certain species may face dwindling numbers and even extinction if they are unable to migrate fast enough to keep up with the changing climate.

Climate change is likely to alter the quantity and quality of the various goods and services that ecosystems provide. For example, climate change is likely to affect the ability of ecosystems to filter air and water pollutants and to control soil erosion, the report indicates.

Modeling studies estimate that the productivity of plants could change little or could increase substantially. However, these productivity changes will not be uniform and some regions could see declines.

While plant productivity may rise, so could decomposition and, with it, the release of carbon to the atmosphere.

The effects of climate change on ecosystems must be considered in the context of a range of human caused impacts on ecosystems, the researchers recommend. Climate change is likely to be particularly damaging for ecological communities and species that have suffered the greatest disruption from human development, the researchers said.


Invasive species like the melaleuca tree could expand their foothold in the U.S. as ecosystems are weakened by climate change (Photo courtesy National Park Service)
Natural ecosystems already under stress because of air and water pollution will have diminished capacity to adapt to climate change. Likewise, habitat destruction and fragmentation will lessen the chances that species will be able to migrate to more suitable climates and habitats.

Because ecosystems are inherently complex, it is hard to predict exactly how ecosystems will respond to climate change, the researchers warn. By protecting natural systems and biodiversity in general, government and community leaders can support the natural ability of ecosystems to adapt to a changing world.

Complete copies of both reports are available at: