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Humans are more at risk from diseases as biodiversity disappears


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People often ask me, "Why should I care if a species goes extinct? It’s not essential to my daily life, is it?"

Well, according to new research published December 2 in Nature, the answer is yes—healthy biodiversity is essential to human health. As species disappear, infectious diseases rise in humans and throughout the animal kingdom, so extinctions directly affect our health and chances for survival as a species. (Scientific American is part of Nature Publishing Group.)

"Biodiversity loss tends to increase pathogen transmission across a wide range of infectious disease systems," the study’s first author, Bard College ecologist Felicia Keesing, said in a prepared statement.

These pathogens can include viruses, bacteria and fungi. And humans are not the only ones at risk: all manner of other animal and plant species could be affected.

The rise in diseases and other pathogens seems to occur when so-called "buffer" species disappear. Co-author Richard Ostfeld of the Cary Institute of Ecosystem Studies points to the growing number of cases of Lyme disease in humans as an example of how this happens. Opossum populations in the U.S. are down due to the fragmentation of their forest habitats. The marsupials make poor hosts for the pathogen that causes Lyme disease; they can also better defend themselves from the black-legged ticks that carry the affliction to humans than can white-footed mice, which, on the other hand, are thriving in the altered habitat—and along with them disease-carrying ticks. "The mice increase numbers of both the black-legged tick vector and the pathogen that causes Lyme disease," Ostfeld said.

The authors focused on diseases—including Lyme, West Nile virus, hantavirus and nine others—around the world. In each case they found that the maladies have become more prevalent during the time in which local biodiversity shrank.

Three of the cases they studied  found that the rise of West Nile virus in the U.S. corresponded to decreases in bird population density.

The researchers also conclude that humans and wildlife really shouldn’t interact. Direct contact with wildlife—say, in the form of the often illegal bushmeat trade—could in turn cause more diseases to jump from animals to humans.

The best solution to both situations: "Preserving large intact areas and minimizing contact with wildlife would go a big step of the way to reducing disease," Keesing said in Nature.

So should you care? Yes you should, if you value your health. A healthy planet equals healthy humans, a lesson it’s really time we learned.

Photo: West Nile virus, via Wikipedia





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  1. 1. gesimsek 1:35 pm 12/7/2010

    In rural areas of Turkey number of certain species of birds like pheasants were decimated because of hunting and three years ago thousands of free range chickens were killed in order to stop the spreading of bird flu. Then, two years ago an infectious disease called Crimean-Congo fever began to kill villagers. It turned out that certain kind of ticks were carrying that disease and infecting humans. Until recently pheasants and chickens were eating a big amount of ticks’ population and thus controlling the spread of the virus. No birds no cure!

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  2. 2. drafter 2:27 pm 12/7/2010

    How ironic a another article in Sciam a poster mentions how there seams to be a goal of scientist to keep humans under control and here this article proves it by the authors suggestion of maintaining places where humans can not go.
    A little note it matters not if your beliefs are religious based or Darwinist mankind came from nature and therefore can interact and live with and in nature.

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  3. 3. Ungolythe 3:32 pm 12/7/2010

    Nowhere in the article did the author’s suggest that there be places where humans can not go. They do, however, suggest "Preserving large intact areas and minimizing contact with wildlife would go a big step of the way to reducing disease," The Earth has limited resources to support humans. To suggest that it may be better for us if we don’t cover the earth entirely in subdivisions and shopping malls is hardly proof of some evil plot by scientists to control humans.

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  4. 4. Trent1492 4:09 pm 12/7/2010

    @Drafter,

    "How ironic a another article in Sciam a poster mentions how there seams to be a goal of scientist to keep humans under control and here this article proves it by the authors suggestion of maintaining places where humans can not go."

    As has already been pointed out: It says no such thing.
    The article is short and easy to understand why did you think you could get away with this dishonesty?

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  5. 5. SirFrancisBacon 1:26 pm 12/11/2010

    There is a book about this topic that I’ve been meaning to read. It’s called Sustaining Life: How Human Health Depends on Biodiversity.

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  6. 6. shrmnnkfr 10:02 am 12/12/2010

    life is a cycle..if one disappears from the process then it will be different, the cycle or process will be carried on by the other specie and what if that specie cannot do what the other extinct specie did? it will be disastrous..if, one by one will get extinct..what will happen… just let ur imaginations run wild

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