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Deforestation: it makes you sick, doesn’t it?

MaleriaMap.jpgPosted on behalf of Emma Marris.

If you were consoled by the news last year that the tropical rainforests are growing back, and that these new forests are “almost as biodiverse as untouched forest”, prepare to be unconsoled.

Even as those secondary forests are growing back, forests both old and new continue to be cut down. And this deforestation is not only driving species extinct and emitting lots of climate-changing carbon dioxide, it is also increasing malaria rates in deforested areas.

Researchers looked at satellite imagery of forest cover in Acre, Brazil, along with reports from health workers there. They conclude in the US Centers for Disease Control and Prevention journal Emerging Infectious Diseases that deforestation bumps up malaria rates in the area by almost 50%.

The Anopheles mosquitoes that carry malaria, in this case A. darlingi, just love the sunlit pools and puddles left in the wake of a good clear cut. Their non-malaria-transmitting brethren prefer the undisturbed forest pools in the shade.

The University of Wisconsin press release quotes co-author Sara Olson as saying “It appears that deforestation is one of the initial ecological factors that can trigger a malaria epidemic.”

This isn’t an entirely new idea. Back in 2008, similar results were found in Kenya, even though the malarial mosquito there is a different species.

The tree-planting nonprofit, Trees for the Future has been using the idea that forests combat malaria to encourage donations. They claim that trees suck up standing water in which mosquitoes breed, provide habitat for the birds and spiders that eat mosquitoes and can even drive them away all by themselves, as in the case of the Indian neem tree (Azadirachta indica), which has seeds that kill mosquito larvae.

So preserving rainforest could prevent malaria, as well as “slow forest loss, conserve biodiversity and preserve local cultures,” turning a win-win-win into a win-win-win-win. And planting trees, especially neem trees, could beat back malaria in places where it is rampant.

Except of course it is never quite that simple. According to the authors of a 2008 review of studies on the topic in Africa, “The relationship between malaria transmission, forest cover and deforestation is complex.” They report on a “generally accepted (though largely qualitative) opinion that deforestation increases the risk of malaria transmission in Africa and tropical America but decreases it in Asia.” Different malaria-carrying mosquitoes are adapted to different microhabitats; deforestation is often followed by agriculture, which, depending on the crop, can be good or bad for these species (rice paddies are some larvae’s dream home, for example).

If ecology and epidemiology were simple, we wouldn’t need ecologists and epidemiologists to unravel such tangles. But for the people in the studied districts in Brazil, deforestation was sickening.

Image: Barry Carlsen, University of Wisconsin, Madison


  1. Report this comment

    amylynn said:

    For those interested in learning more about everyday indigenous life in the Peruvian Amazon, please visit You will see amazing photos, all of them taken by the children who live there. It is a unique, intimate perspective and a true document of their realities.

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    michelle said:

    As a Biology and Earth Science high school teacher (in the midwest), I have always been sickened/sadened by the tragedies afflicted by humans on ecosystems…particularly OUR rainforests. I stress the word “OUR” because my students seem to be so empathetic to world issues…untill you can relate it or connect it to their lives. This is a battle that I struggle with daily! We learn about malaria (and other pathogenic diseases), sickle cell anemia (in genetics and how it ties in with malaria), and ecology (which encompasses biomes, resources, biodiversity, interactions between/among organisms, climate change, human impacts on ecosystems, etc.). Thank you for sharing this information, it is something that I had never really thought about before but the correlation totally makes sense!

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    lanyards said:

    Consequently, many animals and plants that live in the rainforests face the specter of extinction. The extinction of the plants and animals leads to diminished gene pool. The lack of biodiversity and a reduced planetary gene pool could have many unforeseen ramifications, some of which could be fatal to the future of humanity. In addition of course is the SICKNESS ..

    Very good post. thank you for sharing.

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    Samantha said:

    Your post gives me sense. Anyway Deforestation really makes us sick. It’s a human fault. It gives us harmful life. Your post is very interesting to be discuss. I’m going to tell my friends about this topic.

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    bpo projects said:

    Deforestation is so socking for a nature and whole Earth decay as well.If the person are not aware about deforestation it means the nature in danger.

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    Fern Hotels said:

    Its one of the worst things that could have happened to the planet. With no trees, we are sure to face issues soon! Mankind needs to rethink and reorder their priorities before we do such damage as cannot be repaired! Do have a look at our blog where we discuss many issues related to problems faced by the planet and the solutions or work arounds for the same!

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    Jorge Gerônimo Hipólito said:

    The United States could make a proposal to Brazil. For example,

    reforest one million hectares of forests (native) per year, ie one million

    on American soil and one million in Brazil. Thus, we would be tied

    the policy of revitalizing forests. Imagine, after 10 years would be ten

    million hectares, ie, here and there. What do you think of my suggestion?

  8. Report this comment

    Scott Spinella said:

    Great post.Thanks for sharing your post with us.I felt really good after reading it.Thanks again !!!

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