Loss of Large Animals Could Lower Soil Fertility

Researchers from the University of Oxford have warned that the disappearance of large animals like elephants could lead to loss of essential nutrients from the soil.

Their study on soil nutrients has shown that large-scale extinction of "mega fauna" about 12,000 years ago led to the dearth of soil nutrients. The disappearance of large animals today could lead to the same kind of loss. Large animals have essential soil-nutrients trapped in their dung and bodies. As they move from one place to another, they carry these nutrients with them and deposit it in nutrient-deprived regions.

Researchers used mathematical models to analyze the effect of mass extinction of big animals around 12,000 years ago. They focused on animals in the Amazon forest. The study showed that loss of large animals reduced phosphorous dispersal in the area by as much as 98 percent.

The study found that the vanishing of mega fauna led to nutrients like phosphorous concentrating along the river basin. Even after several thousand years, many parts of the forest lacks the essential nutrient.

During Pleistocene epoch- 2.6 million to 11,700 years ago, much of the world looked like the African Savannah. The Amazon forest was teeming with large animals that spread nutrients around the region, AFP reported.

The mathematical model developed by the researchers was similar to the one used by physicists to calculate the extent of heat dispersal. The model accounted for an animal's size, it's diet and the amount of nutrients it carried and dispersed.

The model only requires the average size of an animal along with data about its distribution to calculate how much its disappearance will affect soil quality in the region. The model can help researchers calculate the effect of elephants going extinct in Africa, according to a news release.

"Put simply, the bigger the animal, the bigger its role in distributing nutrients that enrich the environment. Most of the planet's large animals have already gone extinct, thereby severing the arteries that carried nutrients far beyond the rivers into infertile areas. We can also predict the effects of further extinctions - a fate fast approaching many of the large animals that remain - and examine the likely impact thousands of years into the future," Dr Christopher Doughty from the Environmental Change Institute at the School of Geography and the Environment, University of Oxford and lead author of the study.

The study is published in the journal Nature Geoscience.