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Editor's note: Peter Kareiva was a member of the working group that produced the new report by the President's Council of Science Advisors on environmental capital. The views he expresses below are his and not necessarily the position of The Nature Conservancy.

Conservationists have made the orangutan a symbol of what will be lost if we do not halt tropical deforestation. But data tell a more nuanced story. In Kalimantan on the island of Borneo, humans murder so many orangutans each year (on average, between 1,970 and 3,100 annually) that this rate of killing is enough to tip the species towards inexorable extinction. These numbers are part of a new study just published in the journal PLoS One and co-authored by a group of Nature Conservancy scientists, who interviewed almost 7,000 people from 687 villages in Kalimantan.

There is little hope of saving a species like the orangutan unless we know why it is in peril. Unfortunately, conservation often latches onto ideas without much evidence. For example, it used to be thought that orangutans needed pristine old growth forest to thrive. Recently, however, large populations of orangutans have been documented in highly degraded forests. The argument about "save the rain forest to save the orangutan" suddenly got a little weaker.

Of course, massive deforestation is responsible for severe declines in orangutan populations. And the encroachment of villages into forests has put orangutans in more frequent contact with humans, and hence more susceptible to being killed by humans. This orangutan story is not so unique, as increased human-wildlife contact is being seen on every continent in the world: grizzly bears and wolves in the United States, pumas in South America, elephants and tigers in India and orangutans in Indonesia. Friends of mine with direct personal experience wonder how many endangered stellar sea lions in Alaska are shot by people — and I personally have seen fisherman shoot at marine mammals (illegally). Humans have been hunting and killing wild animals for tens of thousands of generations, and we should not be surprised by this type of behavior.

Certainly, when there is human-wildlife conflict, strict laws do not appear to be the answer. It is pretty hard to prove guilt and then prosecute a human for killing a protected species. Indonesia's national law outlawing any killing of orangutans obviously has not been much of a deterrent. The scientists leading the study of orangutan killing suggest that the only effective solution is likely to be cultural and social persuasion. Optimistically, they do not think it will take much to get people to change their behavior in this particular case.

Finally, this story of killing as a major source of orangutan risk should give all conservationists pause. Go to the websites of the premier orangutan conservation NGOs and see if there is any mention of killing on the scale discovered in this recent study. Even within the Conservancy, where we have been working in Indonesia for over a decade, one has to wonder why did it take us so long to uncover this threat to the orangutan?

The answer is perhaps not so bad — it is because we, like all conservationists, are action-oriented and eager to implement strategies based on conventional scientific wisdom. But the startling discovery of a murderous killing rate of orangutans should remind us to never accept conventional wisdom as fact, and to always be collecting fresh data and conducting new studies.

Text by Peter Kareiva for The Nature Conservancy's Cool Green Science Blog.