Populations of large wildlife are declining around the world, while zoonotic diseases (those transmitted from animals to humans) are on the rise. A team of Smithsonian scientists and colleagues have discovered a possible link between the two. They found that in East Africa, the loss of large wildlife directly correlated with a significant increase in rodents, which often carry disease-causing bacteria dangerous to humans. The team's research is published in the Proceedings of the National Academy of Sciences, April 28.
"Our study shows us that ecosystem health, wildlife health and human health are all related," said Kristofer Helgen, curator of mammals at the Smithsonian's National Museum of Natural History and co-author of the research.
Large animals, such as elephants, giraffes, antelope and zebras, have a profound influence on their ecosystems by feeding on vast amounts of vegetation and compacting and disturbing soil. As populations of these large species decline, the ecosystems they once dominated change in many ways. The team's main question was whether the loss of large wildlife influences the risk of people contracting diseases spread by rodentsa pressing question, as more than 60 percent of infectious human diseases are zoonotic.
"Understanding the linkages between biodiversity loss and zoonotic disease is important for both public health and nature conservation programs," said Hillary Young, former Smithsonian post-doctoral fellow and current assistant professor at the University of California, Santa Barbara. "While this correlation has been the topic of much scientific debate, ours is one of the only studies to offer clear experimental evidence." Young is the lead author of the research paper.
Using 24 acres of savanna that had been fenced off for 15 years to keep large animals out in central Kenya, the scientists examined rodent populations inside and outside the area for three years. They also tracked the
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