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How deforestation is helping to spread Ebola

One of the big questions surrounding the current deadly Ebola outbreak in Guinea, Liberia, and Sierra Leone is how the disease spread to humans in the first place.


This map is up to date as of June 20, 2014. CDC/VSPB

In all likelihood, the virus was originally circulating among bats or possibly gorillas in the forests of western Africa. Some experts believe that the disease may have spread to humans via "bushmeat" — someone butchering an infected bat for food, say, and coming in contact with its blood.

The disease then traveled from humans to humans. One possible conduit is through certain funeral rites in which dead bodies are washed by hand, notes John Snow, an epidemiologist at Columbia University. (The first recorded case in the current outbreak was a doctor in the rural town of Gueckedou in Guinea — the virus then spread to those at his funeral.)

That's one plausible scenario, at least. But it's worth noting that there are all sorts of other complex factors at play here that make these scenarios even more likely to occur in the first place. In western Africa, for instance, deforestation is putting humans in closer contact with bats, who may be carrying the disease. So has conflict in Sierra Leone.

Over at Mother Jones, James West and Tim McDonnell have an excellent story on all the human activities that are making Ebola outbreaks more likely. Here's the section on deforestation:

Melissa Leach, the director of the University of Sussex's Institute of Development Studies, lived for several years in the border forests of Guinea where this latest outbreak first began. She says the forest landscape there is complex and ever-changing — a "mosaic." Villages here are surrounded by forest and agriculture, and that means bats — thought to carry Ebola — are everywhere. "I lived in a house in a village in Kissidougou district for two years which was full of bats in its roof," she says.

Human activity is driving bats to find new habitats amongst human populations. More than half of Liberia's forests — home to 40 endangered species, including the western chimpanzee — have been sold off to industrial loggers during President Ellen Johnson Sirleaf's post-war government, according to figures released by Global Witness.

Logging, slash-and-burn agriculture, and chopping down trees for an increased demand for fire wood are all driving deforestation in Sierra Leone, where total forest cover has now dropped to just 4 percent, according to the United Nations Environment Programme (UNEP) which says if deforestation continues at current levels, Sierra Leone's forests could disappear altogether by 2018.

"We see deforestation or incursion into forests, whether it's through hunting or just alteration of landscape, causing people and wildlife to have more contact," says Epstein.

There seems to be a broader pattern here. Other researchers have argued that the overall increase in Ebola outbreaks in Africa since 1994 is at least partly a consequence of deforestation throughout the tropics.

"Extensive deforestation and human activities in the depth of the forests may have promoted direct or indirect contact between humans and a natural reservoir of the virus," wrote researchers in one 2012 study.

If there really is a link, that's bad news. The tropical forest region of western Africa now has one of the highest rates of deforestation in the world. Guinea, Liberia, and Sierra Leone are all watching their rain forests get chopped down at a furious pace. And that raises the possibility that the current Ebola outbreak, which has now claimed more than 500 lives, won't be the last.