A study reported in the journal Current Biology on April 1 has both good news and bad news for the future of African elephants. While about 18 million square kilometers of Africa -- an area bigger than the whole of Russia -- still has suitable habitat for elephants, the actual range of African elephants has shrunk to just 17%of what it could be due to human pressure and the killing of elephants for ivory.
"We looked at every square kilometer of the continent," says lead author Jake Wall of the Mara Elephant Project in Kenya. "We found that 62% of those 29.2 million square kilometers is suitable habitat."
The findings suggest that, if released from human pressures, including the threat of being killed for their ivory, elephants still have great potential for recovery into areas where the human footprint is light. They note that those 18 million square kilometers include many areas where there is still room for peaceful coexistence between humans and elephants as well as others where that prospect is clearly not realistic.
Like many wildlife species, it's long been clear that African elephant populations and their geographic range were shrinking due to killing for ivory, habitat loss, and the growth of human populations. But African savannah and forest elephants can live in many environments, from semi-deserts to tropical swamp forests. Wall's team wanted to better understand how elephants are using the space that's available to them and what's driving their ranging patterns.
To analyze the suitability of habitats over the entire continent at a kilometer-level scale, Wall and his colleagues drew on data from GPS-tracking collars fitted to 229 elephants across Africa by Save the Elephants and its partners over a 15-year period. Using Google Earth Engine, a satellite imagery computing platform, they looked at the vegetation, tree cover, surface temperature, rainfall, water, slope, aggregate human influence, and protected areas in the areas the elephants traversed. This allowed them to determine which habitats can support elephants and the extremes of conditions that they currently can tolerate.
"Combining three powerful tools -- GPS telemetry, continent-wide remote sensing at a fine resolution, and a suite of analytical techniques -- has allowed us to see what factors now control the movements and lives of these two hugely ecologically important species -- and where, if circumstances change, they could range more widely across their historical African home," said Samantha Strindberg of the Wildlife Conservation Society.
The researchers uncovered vast areas of potentially suitable habitat for elephants in the Central African Republic and the Democratic Republic of Congo. The researchers note that forests in those areas recently held hundreds of thousands of elephants but today hold only about 5,000 to 10,000. The study also highlighted the extreme habitats that African elephants do not visit.
"The major no-go areas include the Sahara, Danakil, and Kalahari deserts, as well as urban centers and high mountaintops," said Iain Douglas-Hamilton, the founder of Save the Elephants. "That gives us an idea of what the former range of elephants might have been. However, there's a dearth of information about the status of African elephants between the end of Roman times and the arrival of the first European colonizers."
The tracking data also show that elephants living in protected areas tend to have smaller home ranges. The researchers suggest that's probably because they feel unsafe ranging into unprotected lands. The study notes that approximately 57% of the current elephant range is outside of protected areas, highlighting the limited space presently reserved for their safety. To secure long-term survival of elephants, the researchers say that habitat protection, protection of elephants themselves from illegal killing, and an ethic of human-elephant coexistence will be essential.
"Elephants are generalist mega-herbivores that can occupy fringe habitats," Wall says. "Their range may have shrunk, but if we gave them the chance, they could spread back to former parts of it."
Unfortunately, trends are headed in the wrong direction. "The human footprint is increasing at an accelerated rate and expected to double by 2050, with between 50% and 70% of the planet already experiencing anthropogenic disturbance," the researchers write. "Fragmentation of wildlife habitats by humans has resulted in only 7% of wildlife habitat patches being larger than 100 km2. Development scenarios that accommodate the spatial needs of wildlife leaving large, low-human impact areas of intact habitat, and especially formally protected areas, are urgently required. In the face of increasing human pressures, proactive landscape planning at the local, national, and continental scales are critical, as well as fostering an ethic of human elephant coexistence, if the future of elephants is to be secured."
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