Deforestation May Make Humans More Vulnerable To Infection

[Judi Lynn]

Deforestation May Make Humans More Vulnerable To Infection

ScienceDaily (Feb. 11, 2008) — A new study suggests that socioeconomic factors best explain patterns of the infectious disease American Cutaneous Leishmaniasis (ACL) in Costa Rica. Contrary to the established belief that deforestation reduces the risk of infection, the research shows that deforestation may actually make socially marginalized human populations more vulnerable to infection.

"The classical idea has been that people working or living close to the forest were at risk for the disease, but that view failed to consider such factors as quality of life and general level of health," said co-author Luis Fernando Chaves of the University of Michigan. "Contrary to what was previously believed, the more forest you have, even in a marginal population, the more protected you are against the disease."

The researchers examined county-level ACL case data from 1996 through 2000 for Costa Rica, a country in which approximately 20,000 acres of land are deforested annually to make way for cattle ranching and banana, mango and citrus fruit plantations. In addition to examining such factors as forest cover, rainfall, elevation, and percent of the population living less than five kilometers from the forest edge, the researchers also incorporated an index of social marginalization into their analysis.
(snip)

Putting everything together, the researchers discovered that in fact there is a relationship between ACL and deforestation, but it's not the simple, "less forest, less disease" relationship that previously was believed to exist. Instead, there's a complex connection with El Niño Southern Oscillation (ENSO), a periodic ocean-atmosphere fluctuation in the Pacific Ocean that is an important cause of inter-annual climate variability around the world and also influences disease cycles. In highly deforested counties, socially marginalized human populations are more vulnerable to ENSO's effects, and disease incidence actually is higher, the analysis suggests.

More:
http://www.sciencedaily.com/releases/2008/02/080206090510.htm