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 oroners 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
on 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 des aegyptiosquito 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 threefold 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
US 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." 
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