Disease and Climate Change
Teasing out the links between disease and climate change presents a scientific challenge. Some of the complications: When a disease pops up in a new place, is it because a susceptible population has moved in? Because an over-used drug is no longer effective? Or because the disease carrier has expanded its range? Still, most experts agree: climate change is likely to increase the spread of some diseases.
Lodgepole pines (Pinus contorta) have been a feature of Canada's northern temperate forests for 9,000 years. But today, enormous stands are dead or dying. Why? A fungal disease has invaded the region. Though global climate change is a likely culprit, hotter weather hasn't caused the problem directly. The fungus, Dothistroma sp., needs warm rain to spread; it is "splash dispersed" by spring rain from dead needles on the forest floor. A warming atmosphere means changes in rainfall patterns, and these northern forests are now wetter in spring and summer. This means the fungus can extend its range.
People get malaria when a female Anopheles mosquito injects a parasite, Plasmodium sp., into the bloodstream. There, it multiplies in red blood cells (model). The disease claims nearly a million lives a year in Africa alone, but until now, people living in cool climates—for instance, at high elevations—have generally been safe. Why? Because the parasite inside the mosquito can't reproduce in cool weather. But recent malaria outbreaks in the East African highlands have raised concern about the potential role of climate change. There is now clear evidence that temperatures at higher elevations there have risen since 1950.