Study Suggests Global Warming Won't Spread Malaria
Copyright © 2000 Reuters Limited
September 7, 2000
By Mark Wilkinson
WASHINGTON (Reuters) - Fears that global warming could spread malaria to regions otherwise free of the disease are unjustified, scientists said on Thursday.
Computer models show that global warming will mean drier conditions in northern latitudes, not the steamy, humid conditions needed for malaria-spreading mosquitoes to thrive, the researchers reported in the journal Science.
``We disagree with these silly wild predictions that malaria could spread dramatically because those studies rely on a rather suspect model,'' David Rogers of Oxford University in Britain said in a telephone interview.
Malaria, which kills a million people a year, is spread by mosquitoes. Found mostly in tropical areas, fears are that global warming could create new havens for both mosquitoes and the malaria parasites they carry.
Rogers' main criticism is that many studies seem to have overlooked the essential conditions that keep the parasites that cause malaria alive and instead focused solely on global warming. His study, he said, is more accurate because it combines these key factors and long-term weather forecasts.
``It's not staggeringly brilliant but it's better than what others have done,'' Rogers said.
The study used weather prediction models provided by the Intergovernmental Panel on Climate Change (IPCC), the United Nations agency responsible for forecasting the impact of global warming.
Rogers said this information clearly predicts an increase in global temperature in the future but that this alone would not be enough to make malaria spread to northern latitudes.
``We don't know enough about the spread of malaria in the field, so we use statistical instead of biological information and variables such as humidity, rainfall and temperature,'' Rogers said.
The IPCC computer models predict that the weather in non-malarial regions of the world will grow warmer and drier, Rogers said. ``Many species (of mosquitoes) are constrained by dryness,'' he said.
Rogers' study contradicts other published reports.
Dr. Paul Epstein of Harvard Medical School in Boston believes global warming has already contributed to local outbreaks of malaria in the northern United States and Canada since 1990.
``This study must be flawed in some way because the data is not consistent with what is happening,'' Epstein said in a telephone interview.
Recent heat waves and record temperatures, he argued, have provided a suitable habitat for malaria parasites and the mosquitoes that carry them.
In a recent article published in Scientific American, Epstein wrote that mosquitoes carried on from other parts of the world probably caused these outbreaks, but said the parasites that cause malaria found ``enough warmth and humidity, and plenty of mosquitoes able to transport them.''
Epstein added that studies that conclude malaria will not spread due to global warming ``vastly underestimate the range of mosquito-borne disease.: global warming will create conditions conducive to malaria.''
In parts of Europe, the northern United States and Canada warming is growing at three times the global rate, according to Epstein.
A non-deadly form of malaria, called ``The Ague'' by William Shakespeare, has long been found in Europe and North America. The U.S. Centers for Disease Control and Prevention (CDC) said more than 600,000 people were infected in the United States in1914 alone, before swamps were drained and insecticides introduced to control mosquitoes.
Malaria is found in more than 90 countries and is a threat to more than 40 percent of the world population. An estimated 300 to 500 million cases occur every year, according to the World Health Organization.
WHO says one child dies of malaria every thirty seconds.