Ivory-seeking poachers have killed 100,000 African elephants in just three years, according to a new study that provides the first reliable continent-wide estimates of illegal kills. During 2011 alone, roughly one of every twelve African elephants was killed by a poacher.

In central Africa, the hardest-hit part of the continent, the regional elephant population has declined by 64 percent in a decade, a finding of the new study that supports another recent estimate developed from field surveys.

The demand for ivory, most notably in China and elsewhere in Asia, and the confusion caused by a one-time sale of confiscated ivory have helped keep black market prices high in Africa.

The new study, published in the August 19 issue of Proceedings of the National Academy of Sciences, led by George Wittemyer of Colorado State University, included local and regional population estimates and concluded that three-quarters of local elephant populations are declining.

The study authors conducted the first large-scale analysis of poaching losses using data on illegally killed elephants maintained by CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora).

Wittemyer and his team hope the new information will move the discussion beyond anecdotes and wild guesses. "I think it's the only quantitatively based estimate out there," he said.

Researchers and conservationists hope the analysis will prompt policy makers to take further action to stem the years-long onslaught of poaching, which now threatens the survival of elephants in Africa.

Previous estimates of population declines produced by study co-authors Julian Blanc and Kenneth Burnham, both of CITES, used similar data to examine poaching trends, but those estimates limited the analysis to just 66 sites that were being monitored.

"Nobody's put out any scientifically-based numbers for the continent," Wittemyer said. "People have said numbers, but they're based off guesses. This is the first hard estimate we have at that level."

View Images Confiscated elephant tusks and boxes of figurines carved from ivory sit in the main hall of the National Wildlife Property Repository, in Colorado. Photograph by Kate Brooks, Redux

Targeting the Policymakers

Although conservationists have agreed for years that there's an ongoing poaching crisis with huge implications for the future of African elephants, the authors point out that it's been "notoriously difficult to quantify" the raw number of animals killed by poachers.

In recent years poachers have perpetrated mass killings, such as the 2012 slaughter of hundreds of elephants with automatic weapons in Bouba Ndjidah National Park in Cameroon.

Poachers have also used poisoned arrows to kill iconic individual elephants. In February, a poison-tipped arrow killed Torn Ear, a well-known Kenyan elephant. (See "Mourning the Loss of a Great Elephant: Torn Ear.") Three months later, Satao, another of Kenya's most beloved elephants, was also killed by a poisoned arrow by poachers, who cut off his face to remove his massive tusks. (See "Beloved African Elephant Killed for Ivory—'Monumental' Loss.")

These criminal acts have prompted some official actions, including a U.S. ban on the commercial trade in ivory, but the killings continue at an unsustainable level, with new births unable to keep pace with the killings.

"At the higher policy levels there have been a lot of questions and debate about what the numbers actually are, what they indicate, and how we should be interpreting them," Wittemyer noted.

"There hasn't been a robust scientific piece to rely on definitively as the source. In my mind what we've locked down here and provided the community—and in my mind we're really targeting the policymakers—are definitive numbers on which they can act and on which they can discuss and debate approaches they can take."

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Hard-Won Numbers

In 2002 CITES created a program called MIKE (Monitoring the Illegal Killing of Elephants) to attempt to quantify the number of elephants killed by poachers. Rangers at MIKE sites note all dead elephants they find and determine what proportion of the dead animals was illegally killed.

But the growing number of locations where monitoring is done—the program now monitors between 30 and 40 percent of the population—is still only a portion of the range of the species, and there are big differences in how closely these sites are monitored.

Another problem is that no one knows how many African elephants there are. Elephants are present over many thousands of square miles, which makes it expensive and time-consuming to estimate their overall numbers.

View Images VIRGINIA W. MASON AND BRAD SCRIBER, NGM STAFF SOURCES: COLORADO STATE UNIVERSITY; SAVE THE ELEPHANTS; MONITORING THE ILLEGAL KILLING OF ELEPHANTS (MIKE); DEPARTMENT OF ZOOLOGY, UNIVERSITY OF OXFORD; KENYA WILDLIFE SERVICE; DIANE SKINNER, AFRICAN ELEPHANT SPECIALIST GROUP, IUCN.

The most recent comprehensive population estimate for the continent—a range of between 472,000 and 690,000 elephants—was published in 2007 by the IUCN's African Elephant Specialist Group. That figure was based on the best available data at the time, which for some locations were already nearly a decade old.

The African Elephant Specialist Group continually collects updated population survey data for portions of the continent and shares them with researchers via its public database. But it has yet to produce a new comprehensive population estimate for the continent. Meanwhile, a continent-wide aerial survey, the Great Elephant Census, is under way, with results expected in mid-2015.

Modeling the Numbers

For their study, Wittemyer and his co-authors used the most recent population numbers available from the African Elephant Specialist Group database for well-monitored locations. The researchers calculated that in the absence of poaching, about 3 percent of an elephant population would be expected to die each year.

Applying the percentage of deaths from poaching in 2010 through 2012, derived from MIKE data at the most closely monitored sites, they were able to calculate the percentage, and the numbers, of elephants poached regionally and continent-wide.

Kenneth Burnham, the statistician with the MIKE program who devised this method, used a similar approach to project the number National Geographic magazine used in its October 2012 cover story, "Ivory Worship." The magazine reported that "it is 'highly likely' that poachers killed at least 25,000 African elephants in 2011. The true figure may even be double that."

The new study puts the 2011 number at 40,000 elephants slaughtered at the hands of poachers.

Trevor Jones, of the Southern Tanzania Elephant Project, who didn't participate in the study, said, "I think this paper represents an honest attempt to interpret the MIKE data, and no doubt its results and conclusions are broadly correct in describing an overall trend of large declines in elephant populations across Africa."

He points to continued misgivings about the MIKE numbers because they are based on a smaller number of carcasses than aerial surveys. "Aerial censuses of the Selous Game Reserve," Jones said, "estimate a decline from 2009 to 2013 of 39,000 to 13,000—yet the MIKE data estimate 4,931 elephants poached from 2010 to 2012."

Jones, like many others, is eager for the results of the forthcoming Great Elephant Census. "The best way to update data on population sizes in most areas is by aerial sampling, and I strongly suspect that the census is going to confirm the unprecedented scale of the current crisis for elephants across the continent. Those results cannot come a day too soon."

But aerial surveying has drawbacks too. Forest elephants can't be seen from the air, and assessing their numbers takes labor-intensive foot surveys of dung piles. A recent forest elephant survey took "80 foot-surveys; covering 13,000 km; 91,600 person-days of fieldwork," according to the study abstract.

What We Lose When We Lose Elephants

The huge scale of the losses of African elephants could reduce genetic diversity to the point where healthy and robust populations become dangerously weakened.

But, as Wittemyer said, the problem is greater than genetic diversity. "You're talking about the distribution of species and its ecological role."

Elephants are vital to the web of life in Africa. As a keystone species, they help balance all the other species in their ecosystem, opening up forest land to create firebreaks and grasslands, digging to create water access for other animals, and leaving nutrients in their wake. Sometimes called the "megagardeners of the forest," elephants are essential to the dispersal of seeds that maintain tree diversity.

Since three out of four local populations are declining, those losses have serious ecological implications. "That's a problem we probably didn't speak to strongly enough in this paper," Wittemyer said.

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