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Biodiversity and Human Health: Exploring the Connections

EPA scientists and partners examine the links between biodiversity and human disease

A researcher examining a bird

Gerry Gray was a competitive swimmer in college, has completed triathlons, and regularly trains for long-distance cycling events. But while the occasional 100-mile bike ride won’t slow him down, a weekend camping trip in the woods left him exhausted on and off for years. Gray, a Ph.D. statistician with the Food and Drug Administration, is one of a growing number of people diagnosed every year with Lyme disease.

Gray is not alone. Lyme disease is now the most frequently reported vector-borne disease in the United States. The illness is one of several emerging infectious diseases—along with West Nile encephalitis, malaria, hantavirus pulmonary syndrome, and schistosomiasis—that have been on the rise over the past several decades. 

Over the same time period that public health officials have been tracking the emergence and re-emergence of a number of infectious diseases, ecologists and other scientists have been documenting a steady decline in biological diversity, the number of species and other measures of the variety of life on earth. Are the two related? EPA scientists are working to find out.

“The connections between biodiversity and human health—particularly emerging and reemerging diseases—have not been well studied,” explains EPA environmental and public health scientist Montira Pongsiri, Ph.D, MPH. “EPA established the Biodiversity and Human Health research initiative to develop and sponsor both pilot and long-term, transdisciplinary research projects to better understand how human-caused stressors that lead to biodiversity loss—deforestation, habitat fragmentation, and climate change—are related to the transmission of diseases to humans. We can apply this knowledge to develop environmentally-based (non-chemical) tools, such as ecological indicators of disease risk and quantitative and spatially-explicit models of disease risk, that decision-makers can use to reduce and perhaps prevent disease.”

Pongsiri and research partners present their review of several case studies that examine the links between biodiversity and human health, along with a typology of proposed mechanisms, in a paper in the December 2009 science journal Bioscience.

One EPA-supported project, entitled “Mechanisms Linking Host Biodiversity to Lyme Disease Risk: an Experimental Approach” is being conducted by ecologist Richard Ostfeld, Ph.D. of the Cary Institute of Ecosystem Studies. Ostfeld is a pioneer in exploring how declining species diversity in eastern U.S. forest ecosystems relates to the transmission of the bacterium that causes Lyme disease from animal host to tick, and from tick to human.

Ostfeld is investigating how differences in animal community composition in forest plots relate to the density of black-legged tick vectors and the infection rate among those ticks, and hence risk of Lyme disease transmission. He’s conducting his research in Duchess County, N.Y. a hotspot of Lyme disease.  What he expects to result from these studies is a quantitative model of human disease risk based on ecological data, which can be used by local and state health departments and land use planners.

Other EPA-funded studies include:

  • A Rutgers University-led investigation of the relationships between diversity in plant, bird, and mosquito populations and West Nile virus prevalence in urban wetland communities in northern NJ. Study results can inform new “biocontrol” methods for mosquito control, as well as yield new insights on wetlands preservation that is beneficial to public health.
  • A research team from the University of California at Los Angeles is studying the role that migratory birds play in West Nile Virus transmission. Researchers are using earth observations to better understand how climate and human-caused changes to the environment might predict risk.
  • The studies are fostering partnerships among ecologists, epidemiologists, land use planners, and local and state governments to share scientific advances and new risk prevention strategies that can be applied from individual homes to entire landscapes. The interdisciplinary partners in each study are working together with EPA and Regions to plan the implementation of the research tools and products.

“When we better understand the mechanisms linking biodiversity and human disease through our research, we will be better equipped to develop environmentally-based and behavioral approaches that can simultaneously promote conservation and reduce the risk of human disease—which would be a win-win for the environment and for public health,” says Pongsiri.

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