In 2009, a large, lone elephant named Alexander died along 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 savanna. Now, research inspired by that thinking has found that elephant carcasses can continue to shape ecosystems for years. Thompson regularly walked past Alexander’s body, on his way to a different project. “Seeing the decomposition of that corpse made me curious,” says Thompson, of the South African Environmental Observation Network. Thus a project was born. In life, elephants are ecosystem engineers. When they chew on plants, cut down trees, disperse seeds, fertilize the soil and trample it, 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 ocean floor, 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, the researchers studied elephant carcasses of different ages, measuring changes in the soil, microbes, plants and animals that grazed around them. The results are published in the Proceedings of the National Academy of Sciences. A herd of elephants roams the Kruger National Park in South Africa. Credit: Freemanfootage/Getty Images What happens after an elephant dies? Initially, plant life was extinct. Nutrients from the body leached into the soil, affecting soil chemistry. Around fresh corpses, nitrogen concentrations were up to 3,000 times higher than normal. “That amount of ammonia wasn’t on my bingo card,” says Tercia Midzi, who works in the Kruger National Park. The levels were so high that plants had difficulty growing. Soil-dwelling bacteria were also affected. Although their diversity declined, the activity of those that survived skyrocketed, as a few fast-growing species became dominant. “At really fresh carcass sites, soil nitrogen concentrations can be up to 3,000 times higher,” says the study’s lead author, Courtney Reed. “That’s just crazy.” Credit: Simon Skafar/Getty Images The plants showed a similar pattern. Once soil chemistry softened, plant diversity remained low, and a handful of fast-growing, nutritious species took over. Casing “turns these watery iceberg lettuce grasses into juicy romaine lettuce,” says Deron Burkepile of UC Santa Barbara. This did not go unnoticed. Herbivores returned repeatedly to feed on the nutritious grasses, while their manure added even more nutrients to the soil. The effects persisted for at least eight years, revealing a previously overlooked way elephants shape ecosystems. “It was a powerful reminder that what we see in nature is often shaped by legacies from the past,” says Izak Smit of National Parks South Africa, “even when the causes of those legacies have long since disappeared from view.” More wildlife stories from around the world.
