One-third of the world’s species are now threatened with extinction. It is a massive loss of biodiversity that has serious implications for our health and for the earth’s health: A just-published study in the online journal PLOS Biology says that shrinking biodiversity could mean a rise in tropical diseases including malaria and dengue fever. The study makes a case for why, in fighting human disease, ecological preservation is just as important as medicine and vaccines.
As more and more species of animals and plants face extinction, humans are at greater risk of being affected by parasitic and vector-borne diseases. The latter term refers to bacterial and viral diseases transmitted by mosquitos, ticks and fleas. The reason for the rising risk is that, with a decreasing variety of animal carriers for a disease, an illness’ “life cycle” is less likely to be disrupted, as Matthew Bonds, a researcher at Harvard Medical School and the study‘s lead author, explains to NPR.
Biodiversity Loss Linked to Lyme Disease and West Nile Encelphalitis
The explosion in cases of Lyme disease can be connected to a significant decline in the population of tick hosts (squirrels, mice, opossums and other small mammals) due to habitat degradation in the forest of the Northeast, according to a 2002 study in the Proceedings of the National Academy of Sciences. Opossums can pick off the deer ticks that spread Lyme disease with their claws but as economic development has led to the loss of their homes, Lyme disease has spread to the white-footed mouse, which is simply less able to kill to ticks. As a result, Lyme disease has spread in alarming numbers to humans, with just under 25,000 confirmed cases in 2011 in the U.S.
Another vector-borne disease, West Nile encephalitis, has also risen in the U.S. due to diminishing biodiversity. A 2010 paper in Nature found that crows, who are more likely to remain in urban and suburban environments, are excellent carriers for this disease and much more than other species of birds who have abandoned areas where humans have moved in.
Ecology is a Public Health Issue, Especially in Developing Nations
The new study by Bonds and other researchers offers even more evidence as to why we need to protect endangered species around the world. Socioeconomic factors alone do not account for the spread of infectious and other diseases. Changes in wildlife populations are also factors. As Bonds and his colleagues writes, ”Well-functioning, diverse, ecosystems can serve public health interests.”
Even more, protecting and preserving wildlife has a huge impact on both the health and economies of developing nations around the world. A number of countries with a high level biodiversity such as Laos are among the poorest in the world and at a huge risk of sacrificing priceless wildlife resources (including monkeys and tigers whose numbers are already small) for the sake of economic development to supposedly improve their citizens’ lives.
The medicines that humans create are not enough to stave off disease. We also have to think about where a diseases originates and, just as much, the role that humans clearing forests and building highways and roads can play in causing infectious diseases to sicken more people, in places where they are so poorly equipped to fight them.
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