The new Wisconsin study focused on 54 Brazilian health districts in a corner of the Brazilian Amazon near Peru and where detailed health and population data were collected in 2006 by Brazilian researchers. Combined with high-resolution satellite data of changes in land cover, the health data reveals the large human-health impact of relatively small changes to the forest landscape.
"A 4 percent change in forest cover was associated with a 48 percent increase in malaria incidence in these 54 health districts," notes Olson. "The health data used in the study is of the highest quality and spatial resolution. Unlike previous studies, our data allowed us to zoom in on areas where people are being exposed to malaria and to exclude areas where they are not being exposed."
The health districts reflected in the Wisconsin study are typical of many of the thousands of such districts spread across Brazil and its Amazon region. Since 2001, the Brazilian Ministry of Health has similarly monitored and treated malaria in more than 7,000 districts. Deforestation in the districts, says Olson, is occurring as it typically does in Amazonia, and occurs mostly near rivers, the backbone of the region's transportation system, and spreads outward.
The new work, argues Patz, an authority on environmental change and human health, shows how deforestation and land clearing contribute to malaria's dynamic at the frontier of settlement. "In 2006, the county that encompasses these health districts was in the top five of all Brazilian counties with malaria," Patz says. "Even after we adjusted for human populations, access to healthcare and other factors, malaria hotspots paralleled locations with the most destruction of rainforests."
The message from the study, say Olson and Patz, is that tropical forest conservation may benefit human health more than we realized.
"Land-management practices show promise as useful interventions to reduce malaria
|Contact: Jonathan Patz|
University of Wisconsin-Madison