Recent research has predicted that climate change may expand the scope of human infectious diseases. A new review, however, argues that climate change may have a negligible effect on pathogens or even reduce their ranges. The paper has sparked debate in the ecological community.
In a forum in the April issue of Ecology, Kevin Lafferty of the U.S. Geological Survey's Western Ecological Research Center suggests that instead of a net expansion in the global range of diseases, climate change may cause poleward range shifts in the areas suitable for diseases as higher latitudes become warmer and regions near the equator become too hot.
The newly suitable areas for diseases will tend to be in more affluent regions where medicines are in widespread use and can more readily combat the diseases, Lafferty says. He cites model estimations that the most dangerous kind of malaria will gain 23 million human hosts outside of its current range by the year 2050, but will lose 25 million in its current range.
"The dramatic contraction of malaria during a century of warming suggests that economic forces might be just as important as climate in determining pathogen ranges," Lafferty says.
Mercedes Pascual of the University of Michigan sees the situation very differently. Pascual is the lead author of one of five Forum papers published in response to Lafferty. Although she agrees that disease expansion in some areas could be accompanied by retraction in others, she emphasizes that disease range does not always correlate with the number of humans infected. In regions of Africa and South America, for example, humans have historically settled in high latitudes and altitudes. If climate change makes these areas more fit for mosquito breeding and for pathogen development, she writes, then a number of infections could expand. She notes that scientists are already seeing evidence of this pattern.
"It would be very unfortunate if the
|Contact: Christine Buckley|
Ecological Society of America