In 2009, a large, lone elephant called Alexander died beside a road in South Africa’s Kruger National Park. Over the next few months, researcher Dave Thompson watched what happened to the carcass and wondered how it was affecting the savannah.
Now, research inspired by that thought has found that elephant carcasses can continue to shape ecosystems for years.
Thompson passed Alexander’s body regularly, en route to a different project. “Watching the decomposition of that carcass got me curious,” says Thompson, from the South African Environmental Observation Network. So, a project was born.
In life, elephants are ecosystem engineers. When they munch plants, fell trees, disperse seeds, fertilise the soil and trample the ground, they create opportunities for other species to thrive. But what happens to that influence when an elephant dies?
When a whale dies and sinks to the bottom of the ocean, its carcass can become a rich source of nutrients, sustaining life for decades. Thompson wondered if something similar was happening on land.
To find out, researchers studied elephant carcasses of different ages, measuring changes in the soil, microbes, plants and grazing animals around them. The results are published in the Proceedings of the National Academy of Sciences.
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What happens after an elephant dies?
Initially, plant life was snuffed out. Nutrients from the body leached into the ground, affecting the soil chemistry. Around fresh carcasses, nitrogen concentrations were up to 3,000 times higher than normal. “That amount of ammonium was not on my bingo card,” says Tercia Midzi, who works at Kruger National Park. Levels were so high that plants struggled to grow.
Soil-dwelling bacteria were affected too. Although their diversity went down, the activity of those that survived rocketed, as a few fast-growing species became dominant.
Plants showed a similar pattern. Once the soil chemistry mellowed, plant diversity remained low, with a handful of nutritious, fast-growing species taking over. The carcass “turns these grasses from watery iceberg lettuce into a juicy romaine,” says Deron Burkepile from UC Santa Barbara.
This did not go unnoticed. Herbivores repeatedly returned to feed on the nutritious grasses, while their manure added yet more nutrients to the soil.
The effects persisted for at least eight years, revealing a previously overlooked way that elephants shape ecosystems.
“It was such a powerful reminder that what we see in nature is often shaped by legacies from the past,” says Izak Smit from South African National Parks, “even when the causes of those legacies have long since disappeared from view.”
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