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Earth's Endless Summer Causing More Disease

Report says illness affecting all living organisms

THURSDAY, June 20, 2002 (HealthDayNews) -- Perpetual summer is coming to Earth, and it's not going to be an endless procession of beach parties and sea breezes. As the world gets warmer, it's also likely to get sicker -- literally.

A two-year study out of the National Center for Ecological Analysis and Synthesis (NCEAS) finds climate changes will likely mean an increase in infectious diseases affecting both plant and animal systems, possibly threatening the survival of entire species. The research appears in tomorrow's issue of Science.

"This is a very important paper that brings together the issues of diseases in plants and wildlife and humans. By looking at the cross-section, one gets an even stronger picture of the impact of warming on disease," says Dr. Paul Epstein, associate director of the Center for Health and the Global Environment at Harvard Medical School. "One gets a very strong signal that warming is certainly increasing and contributing to the emergence and resurgence and redistribution of infectious diseases."

This study is the first to investigate disease epidemics across entire plant and animal systems.

"We're looking for general patterns across as many diseases of as many organisms as possible, including oysters, coral, plants and songbirds, and we're seeing striking similarities in the patterns of disease spread," says Richard Ostfeld, co-author of the study and an animal ecologist at the Institute of Ecosystem Studies in Millbrook, N.Y. "The similarities are striking enough across the board that we think this has to be taken seriously now."

The study authors began their research with two known developments: the warming of the earth's climate and the fact that certain diseases, such as malaria and Dengue fever, are spreading northward from the tropics and up into mountains.

The question then became: How are these two linked? And the answer: Possibly in several different ways.

Pathogens, microorganisms and vectors such as mosquitoes tend to flourish in higher temperatures. In the Hawaiian Islands, for example, mosquitoes used to stay below 2,500 feet, where it was warmer. Now, thanks to global warming, they've moved up in to the mountains where they are threatening the last populations of honeycreepers (songbirds unique to Hawaii) with avian malaria.

Reproduction and biting also both tend to increase in hotter areas. Winter acts as a curb on population growth.

Warmer weather may also make hosts more susceptible to infection.

The spread of disease may not come from the warming per se, but from changes in rainfall patterns and humidity caused by the higher temperatures. For example, Rift Valley fever, a virus spread by mosquitoes, is strongly linked to heavy rains. "One disturbance sets you up for further disturbances," Epstein says. "Once the system is disrupted, it's more vulnerable."

Biodiversity is also suffering, as pathogens contribute to declining numbers of lions, cranes and vultures, to name a few.

"We've underestimated the rate at which climate would change, the rate at which biological systems would respond to that change, the cost to our society and to our agriculture, to our forest, to our health from all of this," Epstein says.

Believe it or not, the news could have a silver lining.

"The good news is that this may serve as a wake-up call," he continues. "This can lead us to address how we're developing, and how we power that development. I don't want to say it's too late. I like to think that systems can be restabilized."

Earlier this month, the Bush administration reversed course and acknowledged in a report to the United Nations that human activity is largely responsible for global warming. However, the administration still opposes a treaty aimed at cutting greenhouse gases, and doesn't plan to follow the report's recommendations aimed at halting the problem.

What To Do

For more information on global warming, check out Global Warming: Early Warning Signs or the Environmental Protection Agency.

SOURCES: Richard Osfteld, Ph.D., animal ecologist, Institute of Ecosystem Studies, Millbrook, N.Y.; Paul Epstein, M.D., associate director, Center for Health and the Global Environment, Harvard Medical School, Boston; June 21, 2002, Science; photo by Craig Packer, courtesy of Science
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