Species down disease up
The extinction of plant and animal species can be likened to emptying a museum of its collection, or dumping a cabinet full of potential medicines into the trash, or replacing every local cuisine with McDonald's burgers.
But the decline of species and their habitats may not just make the world boring. New research now suggests it may also put you at greater risk for catching some nasty disease.
"Habitat destruction and biodiversity loss,"—driven by the replacement of local species by exotic ones, deforestation, global transportation, encroaching cities, and other environmental changes—"can increase the incidence and distribution of infectious diseases in humans," write University of Vermont biologist Joe Roman, EPA scientist Montira Pongsiri, and seven co-authors in BioScience. Their study, "Biodiversity Loss Affects Global Disease Ecology," will appear in the December issue of the journal, available on-line from December 7, 2009.
Diseases Go Global
"Lots of new diseases are emerging, and diseases that were once local are now global," says Roman, a wildlife expert and fellow at UVM's Gund Institute for Ecological Economics. "Diseases like West Nile Virus have spread around the world very quickly."
This is not the first time humans have faced a raft of new diseases. About 10,000 years ago, humans invented farming. This move from hunting to agriculture brought permanent settlements, domestication of animals, and changes in diet. It also brought new infectious diseases, in what scientists call an "epidemiologic transition."
Another of these transitions came with the Industrial Revolution. Infectious diseases decreased in many places while cancer, allergies and birth defects shot up. Now, it seems, another epidemiologic transition is upon us. A host of new infectious diseases, like West Nile Virus, have appeared. And infectious diseases thought to be in decline, like malaria, have reasserted themselves and spread.
"Ours is the first article to link the current epidemiological transition," says Pongsiri, an environmental health expert in EPA's Office of the Science Advisor, "with biodiversity change, decline and extinction." "People have been working on this in individual diseases but no one has put all the studies together to compare them," says Roman.
In 2006, he and Pongsiri gathered a group of scientists and policy analysts with expertise in a range of the new diseases being observed- including West Nile virus as well as malaria, the African parasitic disease schistosomiasis, hantavirus pulmonary syndrome, and several others. From that meeting, the forthcoming BioScience study developed.
"We've reviewed all those studies and show that emergence or reemergence of many diseases is related to loss of biodiversity," says Pongsiri. "We've taken a broad look at this problem to say that it's not just case-study specific," she says. "Something is happening at a global scale."
It is new to think about biodiversity - and therefore, species and land conservation - as integral to public health. Until recently, almost no epidemiologists, nor medical schools, were framing questions of human infectious disease prevention in terms of, say, habitat structure, promoting genetic diversity in non-human species, or protecting animal predators as ecosystem regulators. Human diseases, goes the conventional thinking, are best understood and treated by looking at humans.
"Now there is the beginning of a movement to bring epidemiology and ecology together," says Pongsiri. "From 2008, we also added the sub-title African Protected Area Conservation and Science, to capture the new aims and aspirations for the journal."