WASHINGTON, D.C. -- Coroners won't write "death by global warming," but that could be an ultimate cause as millions succumb to disease in an increasingly unhealthy environment, a Cornell University ecologist warns.
Speaking today (Feb.18) at the annual meeting of the American Association for the Advancement of Science (AAAS), in a session on "Human Health and Climate Change," David Pimentel said global warming will create a favorable climate for disease-causing organisms and food-plant pests -- but a much more challenging planet for humans struggling to survive.
"Right now the evidence of significant global climate change is minimal, but there are already noticeable increases in human diseases worldwide," said Pimentel, a professor of ecology and of entomology in Cornell's College of Agriculture and Life Sciences. "Most of the increase in disease is due to numerous environmental factors -- including infectious microbes, pollution by chemicals and biological wastes, and shortages of food and nutrients -- and global warming will only make matters worse."
Pimentel was the co-organizer, with Laura Westra of Sarah Lawrence College, of the human health session. Also speaking were Rita R. Colwell, director of the National Science Foundation; Jonathan Patz, Johns Hopkins School of Public Health; and Paul R. Epstein, Harvard Medical School. The Cornell ecologist pointed to seven ominous trends:
-- Today, infectious disease causes approximately 37 percent of all deaths worldwide, but the estimated number of deaths due to a variety of environmental factors is higher and still growing. "Environmental diseases," he said, are attributed especially to organic and chemical pollutants, including smoke from various sources such as tobacco and wood fuels.
-- More than 3 billion people currently are malnourished -- the largest number and proportion of humans in desperate need of food and nutrients in human history -- and that number increases every year. Malnutrition increases susceptibility to infectious and environmental diseases, such as diarrhea and pollution-related illnesses, Pimentel observed.
-- A population increase to 12 billion in the next 50 years (based on current growth rates) will exacerbate the spread of disease globally, the Cornell ecologist said. Densely crowded urban environments, especially those without adequate sanitation and nutrition, should be of great public-health concern because they are sources of disease epidemics. Dengue fever, spread by the Aedes aegypti mosquito breeding in old tires and other water-holding containers, is expanding rapidly in crowded tropical cities. With global warming, this mosquito and others will spread north, transporting dengue and other diseases from the tropics.
-- Waterborne diseases -- already accounting for nine out of 10 deaths from infectious disease in developing countries -- will become more prevalent in a warmer, more polluted and crowded planet. For example, only eight of India's 3,120 towns and cities have full wastewater treatment facilities. Hundreds of millions of people in India and other developing countries are forced to use untreated water for drinking, bathing and cooking.
-- Today, air pollutants adversely affect the health of more than 4 billion people worldwide, and air quality in many places is getting worse. The number of automobiles worldwide is growing approximately three times faster than the world population. Meanwhile, an expanding world population is burning more fossil fuels for domestic and industrial purposes. The grim history of lung cancer -- a three-fold increase from 1950 to 1986 -- could be repeated, Pimentel predicted, in developing countries. About 4 billion people in developing countries who cook with wood and coal over open fires suffer continuous exposure to smoke. Wood smoke is estimated to cause the death of 4 million children each year.
-- The more than 3 billion of the world's people who are malnourished increasingly are susceptible to infectious and environmental diseases, the Cornell ecologist said, noting that cropland has been diminished by 20 percent in the last decade, per capita fertilizer production has fallen by 23 percent and per capita irrigation water supplies have dropped by 12 percent.
-- And increasing global climate change will result in a net loss of available food, the ecologist said. "Although there may be some benefits in crop production from warmer climates, these beneficial effects will be more than offset by the projected decline in rainfall in critical crop-growing regions like the U.S. Corn Belt," he said. Crop losses from pest insects, plant diseases and weeds will increase in a warmer climate, Pimentel suggested. As it is, insect pests, plant pathogens and weeds cause the loss of more than 40 percent of the world's food -- despite the application of 5 billion pounds of pesticides each year.
"We're seeing the first signs that global climate change can influence the incidences of human disease," Pimentel said. "This change, combined with population growth and environmental degradation, will probably intensify world malnutrition and increases in other diseases as well."