Elephants are ecosystem engineers. They trample trees, loosen soil with their tusks, and can even create trails and watering holes. According to a new study published in the Proceedings of the National Academy of Sciences, these massive beasts continue to sculpt the savannas long after their deaths.
To investigate the impact of elephant carcasses on the ecosystems, biologists from the University of California, Santa Barbara spent nearly eight years sampling the soil and plant life from 40 different carcass sites scattered throughout South Africa’s Kruger National Park.
Read more: “Is Poaching Causing Elephants to Evolve Without Tusks?”
“My intuition was that, since the carcass was only physically present for a relatively short period, its effect would also be rather muted and transient,” study co-author Izak Smit of the South African National Parks said in a statement. “However, a very different picture emerged when the lab results came back.”
The team discovered a cascade of environmental changes that started unfolding soon after death. First, nutrients from the elephant corpses leached into the ground, altering soil chemistry with nitrogen levels spiking dramatically. “At really fresh carcass sites, soil nitrogen concentrations can be up to 3,000 times higher,” study co-author Courtney Reed of UC Santa Barbara explained. “That’s just insane.”
Rather than stimulating growth, these sky-high nitrogen levels made the soil toxic to plants, but not to the microbes living in the dirt. With a colossal influx of nutrients, bacteria rapidly proliferated—but only a few species. According to the team, a handful of fast-growing bacteria likely out-competed the rest, resulting in a dearth of microbial diversity.
After soil nitrogen levels settled down a bit, plants started to grow, but the researchers found they followed the same pattern as the microbes, with just a few species dominating the carcass site (mostly grasses). According to the team, the nutrient hot spot resulted in a biodiversity cold spot, a dynamic that was present throughout the nearly eight-year study period.
Analysis of the plant leaves also revealed they contained more nutrients. “It turns these grasses from watery iceberg lettuce into a juicy romaine,” senior author Deron Burkepile of UC Santa Barbara said. These lush grasses provided food for grazing herbivores for years, and their droppings kept the sites fertilized.
It’s a lot of ecological activity from just 40 elephant carcasses, and per the team, around 600 elephants die in the preserve each year. Of course, tens of thousands of years ago when megafauna were plentiful, this particular ecological cycle would have been more common. Now elephants are among just a few species of massive animals left, and they’re also endangered.
“Given the magnitude, duration, and ecosystem-spanning integration of these impacts, the loss of megacarcasses could represent a fundamental shift in the structure and function of ecosystems across the globe,” the researchers concluded. 
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Lead Image: Courtney Reed
