A $7 million, comprehensive census of African elephants has found that the population decreased by nearly a third between 2007 and 2014.

The Great Elephant Census was conducted over three years, and set out to effectively count every savanna elephant in 18 countries in Africa, accounting for 93 percent of the savanna elephants in those countries. The conclusion — that the population declined by 144,000 animals in just seven years — is sobering.

The results were published in the journal PeerJ.

"If we can't protect the world's largest land mammal, the prognosis for wildlife conservation is bleak," says Mike Chase, the lead scientist on the project and the founder of an elephant conservation group based in Botswana called Elephants Without Borders.

The survey took enormous resources to pull off. It was funded in part by an American philanthropist, Paul Allen, and was a collaboration between Elephants Without Borders and government and non-government groups in the 18 countries surveyed.

Because individual countries have been responsible for counting their own elephant populations until now, the data from past years was not standardized. Different governments counted animals at different frequencies, using different methods. The Great Elephant Census changed that, providing a standardized baseline of the savanna population across the 18 nations.

The team used small aircraft to fly over enormous swaths of land, recording themselves counting and photographing the elephants they saw. Technical advisers meticulously combed through the data to make sure they weren't counting elephants twice — a concern because the animals move.

Past estimates of the elephant population in Africa ranged from around 400,000 to over 630,000, and there was a lot of disagreement about the numbers. The Great Elephant Census estimate, based on the most rigorous survey so far, finds there are just 352,271 elephants in 93 percent of the animals' range.

Much of the decline in the elephant population is due to illegal poaching by people who sell elephant tusks on the Chinese market, as NPR has reported. Past estimates of how many elephants are illegally killed were based on models and incomplete carcass counts, as opposed to comparing population numbers. The new survey finds tens of thousands of elephants are being killed each year.

"A key component of this is not only counting live elephants but looking to really develop a master plan for elephant protection across Africa," says team member Andrew Parker of African Parks, a cross-border park management agency, in a video about the elephant census.

Many governments have tried to prevent illegal elephant hunting by establishing parks and disrupting the market for ivory, which drives poachers to go after the animals. Kenya has held public ivory-burning events for years — at the most recent one, in April, the government burned the tusks of nearly 7,000 elephants.

In a statement after the results were published, the deputy head of the U.N. Environment branch, Ibrahim Thiaw, released a statement saying elephant poaching "makes no sense on any level — moral, economic or political."

Thiaw continues:

"Elephants are already locally extinct in my own country, Mauritania, and I do not want to see this happen anywhere else –-an imminent possibility in Cameroon and Mali, and further down the line in other countries, unless we accelerate action...."As depressing as these numbers are, I hope they act as a further spark for action and change. We know how to solve the crisis. The Great Elephant Census tells us we must act, and now."

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