Elephants Keep Reshaping The Land Long After They’re Gone

One Elephant Carcass Can Change the Ground for Seven Years or More

A fallen elephant leaves a lot more behind than bones. Its body can flood the soil beneath it with ammonium, a nitrogen compound released as flesh breaks down, at levels averaging 31 times higher than normal. The surge comes with a sharp drop in the variety of plants and microbes living there. Even so, hungry impala and buffalo keep showing up, foraging at roughly triple the usual rate.

Researchers in South Africa’s Kruger National Park found these effects lasted at least seven years, and probably longer, since many of the oldest sites showed no sign of fading.

A drop in variety is the opposite of what happens at sea, where a whale carcass sinking to the ocean floor feeds a thriving community for decades. On land, according to the study in PNAS (Proceedings of the National Academy of Sciences), elephant carcasses thin out the species around them while still speeding up the chemistry and animal traffic.

Forty Elephant Carcasses Show Soil Nutrients Stay High for Seven Years

Reaching that conclusion meant sampling 40 elephant carcass sites across two soil types, one sandy and one rich in clay. Every elephant was an adult, and each had died anywhere from 8 days to nearly 8 years earlier, from causes including old age, illness, injury, and fights. Park staff located the carcasses through ground patrols, aerial surveys, and gatherings of scavengers such as vultures and hyenas. Researchers mostly compared sites of different ages, a bit like flipping through a time-lapse, setting soil and grass collected within a few feet of the bones against baseline samples from about 50 feet away. Lab tests counted the kinds of bacteria and fungi in the soil and measured how busy those microbes were. Plant surveys, grass-chewing scores, and camera traps at eight carcass sites filled out the picture.

Alongside the ammonium surge, nitrate (another nitrogen compound) ran about 7 times higher and phosphorus, a nutrient plants need to grow, about 3 times higher. Phosphorus barely dropped over the 7.7 years, and ammonium and nitrate stayed above normal at the oldest sites. A chemical fingerprint in the nitrogen pointed to an animal source.

Elephant Carcasses Cut Microbe and Plant Variety While Boosting Soil Activity

Carcass sites were typically marked by bare soil and a field of bones. Bacteria became less varied near the carcasses and never rebounded during the study. Fungi dropped too but recovered over time. Plant variety also stayed low through the whole study, while the amount of grass growing slowly recovered but stayed below normal for most of that stretch.

Soil with more ammonium held fewer kinds of bacteria and plants. Gardeners know what too much fertilizer does to a lawn, and the authors consider ammonium’s toxicity to plants a likely reason fresh carcass sites struggled. Microbial activity, meanwhile, ran higher for one to two years before settling back to normal.

Impala and Buffalo Keep Returning to Elephant Remains as Grazing Climbs With Age

Grass at carcass sites held about 1.5 times more nitrogen than grass elsewhere, and animals seemed to notice. Richer grass is better food, which is likely the draw. Cameras recorded more than 24,000 impala and buffalo, the two most common plant-eaters, and both species foraged at carcass sites far more often than at comparison spots nearby. Grazing scores told a similar story, with the gap between carcass sites and surrounding ground widening as carcasses aged. The researchers suspect a feedback loop, in which visiting herds leave dung and urine that keep the soil rich and draw more herds. They flagged that idea as untested.

Smaller animals leave much briefer marks. The highest nitrogen readings at elephant sites ran roughly 14 times those reported near moose carcasses and 20 times those near kangaroo carcasses in earlier studies. Sheer size likely explains the gap, since elephants weigh up to 13,000 pounds and release hundreds of pounds of nutrients into one patch of ground. That patch reaches roughly 16 feet out from the bones, about the footprint of a small apartment. Soil type mattered too, with effects starting stronger in the sandy soil but likely lasting longer in the clay-rich soil, which holds nutrients better.

Hundreds of Elephant Deaths a Year Could Leave Thousands of Altered Patches

Kruger holds about 30,000 elephants, and roughly 600 die there each year. From those figures, the authors estimate around 4,000 carcasses at any given moment could be shaping the park’s ecology, though that number is a calculation rather than a count. Elephants, rhinos, and their relatives were once found worldwide, from the tropics to the poles, so carcasses like these probably played the same role in many ecosystems that no longer have them.

Elephants are declining from human exploitation and habitat loss, and shrinking herds mean fewer of these long-lasting patches. Conservation plans that count only living elephants miss part of what these animals do for the land.

---