Malaria Increases with Deforestation in Brazil

A 4 percent decrease in forest was associated with a nearly 50 percent rise in malaria cases in western Brazil. Christopher Intagliata reports

Illustration of a Bohr atom model spinning around the words Science Quickly with various science and medicine related icons around the text

Join Our Community of Science Lovers!


On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.


You know saving the rainforest is good for biodiversity. But it may also be a boon to human health. That's because less clear-cutting may mean less malaria, according to a paper out this week in the journal Emerging Infectious Diseases. [Sarah Olson et al., http://bit.ly/b6iFgT]

Researchers looked at stats for 2006 from 54 health districts in western Brazil. The sites had more than 15,000 cases of malaria. The investigators compared those cases to deforestation in the same health districts over the previous 10 years. They found that a loss of just four percent of forest cover was associated with nearly 50 percent more malaria cases. And malaria risk was highest five to 10 years after the jungle was cleared.

Not all mosquitoes carry malaria. But the human-loving species Anopheles darlingi does, and previous studies have shown that it thrives in disturbed areas. In fact, you're over 200 times more likely to find one of them biting you in a clearing than you are deep in the jungle, where other more benign species compete with them for blood.

So how much clear-cutting is too much? We don't know yet—but an intact swath of rainforest appears to provide free public health services.

—Christopher Intagliata

[The above text is an exact transcript of this podcast.]

It’s Time to Stand Up for Science

If you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.

I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.

If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.

In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.

There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.

Thank you,

David M. Ewalt, Editor in Chief, Scientific American

Subscribe