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In a climate-warmed world, the mosquito that spreads malaria could expand into temperate areas.
Photographed in Ariquemes, Brazil, where most of the town’s inhabitants suffer from malaria.

Currently, most evidence linking climate warming
to disease outbreaks is circumstantial. Nonetheless, data
linking climate warming and human health problems are
accumulating. More frequent and more severe heat waves
during summer have increased the number of heat-related
illnesses and deaths. Mosquitoes and other disease carriers
are expected to expand their range into the newly warm
areas and spread dengue fever, schistosomiasis, yellow fe-
ver, and malaria (ˆ}ÕÀiʙ°£Ó). According to the World
Health Organization, during 1998, the fourth warmest
year on record, the incidence of malaria, Rift Valley fever,
and cholera surged in developing countries.
An increasing number of studies report measurable
changes in the biology of plant and animal species as a
result of climate warming. Climate change also affects
populations, communities, and ecosystems. In Environ-
mental InSight: The Effects of Global Climate Change, we re-
port on the results of several of the hundreds of studies
conducted thus far.
Rising temperatures in the waters around Antarctica
have led to a decline in the populations of shrimp-
like krill and Antarctic silverfish, major food sources
for Adélie penguins, reducing Adélie penguin popula-
tions (ˆ}ÕÀiʙ°£Î>). Warmer temperatures also cause
higher rates of reproductive failure in these penguins by

producing puddles of melted snow that kill developing

chick embryos at egg-laying sites.

Worldwide, many frog populations have plummeted;

these include Puerto Rico’s national symbol, the tiny tree

frog known as coqui (ˆ}ÕÀiʙ°£ÎL). Warmer tempera-

tures and more frequent dry periods have stressed the

coqui, making them more vulnerable to infection by a

lethal fungus.

Ecosystems considered at greatest risk of climate-

change loss are polar seas, coral reefs, mountain ecosys-

tems, coastal wetlands, and tundra. Water temperature

increases of 1° to 2°C (1.8° to 3.6°F) cause coral bleach-

ing, which contributes to the destruction of coral reefs

(ˆ}ÕÀiʙ°£ÎV). In 1998, when tropical waters were some

of the warmest ever recorded, about 10 percent of the

world’s corals died.

As atmospheric CO 2 increases, some of it dissolves in

the ocean, producing carbonic acid (ˆ}ÕÀiʙ°£Î`). The

consequent acidification could be disastrous for shelled

sea animals, particularly zooplankton at the base of the

marine food web; the acid would attack and dissolve

away their shells. Increased acidity also exacerbates coral

bleaching. It could take centuries for the atmosphere–

ocean CO 2 balance to stabilize, so even if emissions cease,

the ocean will continue to acidify.

Global Climate Change 227