Elephant carcasses enrich savannah soil for years after death, study finds

Elephant carcasses release nutrients that enrich the soil and attract grazing animals for more than seven years after death, according to a new study in South Africa's Kruger National Park.

"What we didn’t know was whether those impacts that are so significant when they’re alive could actually continue after they die," Courtney Reed, lead author of the paper published in Proceedings of the National Academy of Sciences on Monday, told As It Happens.

"Their bodies contain so many nutrients, tons of carbon and nitrogen and phosphorus, we wanted to understand if the nutrients from those carcasses could actually continue to play a role in the ecosystem."

READ MORE: Seven molecules in human milk linked to infant growth and maternal nutrition

READ MORE: Water reacts with plastic to create harmful particles, new study finds

Researchers examined soil chemistry, biodiversity and animal grazing around the massive carcasses.

They found decomposition released "enormous pools of nutrients" into the earth, stimulating soil microbial activity and helping nutrient-rich plants grow.

This attracted herbivores to the site long after any remaining signs of the elephant carcass were gone.

"Then you have herbivores like zebra and buffalo and rhinos who are all coming in and they’re selectively chewing on these nitrogen rich grasses," Reed said.

"So you actually get this burst of herbivore activity that continues for years after the elephants died."

Grazing animals and scavengers continue to visit these burial sites years later, further enriching the soil through their waste.

For Reed, that cycle of renewal is one of the study’s key takeaways: the potential for positive feedback loops to keep influencing the surroundings long after the elephant’s death.

However, the high concentration of nutrients initially kills off vegetation on the site, leaving large bare patches or "cold spots" in biodiversity.

"Too much of a good thing isn’t always a good thing," Reed said.

"You have this huge pulse of nitrogen, often in the form of ammonium, which at really high concentrations can actually be really toxic to plants."

Over time, the ecosystem begins to recover as the excess ammonium dissipates and bacteria convert some of it into nitrate, a form of nitrogen that plants can more readily absorb.

The vegetation that returns is particularly rich in nitrogen, an important source of protein for herbivores.

Chase LaDue, an elephant ecologist and curator of research at the Oklahoma City Zoo not involved in the study, said the paper's findings highlight how delicately balanced an ecosystem must be.

In the African savannah, where biodiversity is shaped in part by natural disturbances, an elephant carcass can help sustain the ecosystem, he said.

But if the habitat has shrunk due to humans encroaching on it, those carcasses can instead disrupt the balance.

"If enough elephants die in a very concentrated space, that has an impact on the biodiversity that sort of can’t be spread out as it would in a more undisturbed larger landscape," LaDue said.

"This area of southern Africa has a lot more elephants than the landscape can support and so this just may be another reason even after the elephants have passed, that the landscape is negatively impacted by being so restricted by human activity."

With files from CBC News