Farmed soils are thinning across the globe, study finds

Sept. 15 (UPI) -- More than 90 percent of traditionally farmed soils are thinning, according to a new global survey of soil erosion rates.

To estimate the longevity of soils across the globe, researchers in Britain, Belgium and China compiled soil erosion data from 255 locations in 38 countries on six continents. Researchers calculated how long it would take for the top foot of soil -- the topsoil humans rely on to grow food -- to be completely eroded, the so-called soil lifespan.

The data -- published Tuesday in the journal Environmental Research Letters -- showed roughly 16 percent of the conventionally farmed soils, including soils in Australia, China, Britain and the United States, have lifespans of less than a century.

"Our soils are critically important and we rely on them in many ways, not least to grow our food," lead study author Dan Evans said in a news release.

"There have been many headlines in recent years suggesting that the world's topsoil could be gone in 60 years, but these claims have not been supported with evidence," said Evans, a researchers at Lancaster University in Britain. "This study provides the first evidence-backed, globally relevant estimates of soil lifespans."

The nutrients and organic matter found in topsoils are vital to not only farming, but a variety of ecosystems services. More must be done, authors of the latest research argue, to slow soil erosion rates and preserve soil health.

While the latest soil survey findings paint a gloomy picture for traditionally farmed soil, the outlook is rosier for soils managed with conservation strategies, which suggests a turnaround for degraded soil is possible.

"What our study also shows is that we have the tools and practices to make a difference -- employing the appropriate conservation methods in the right place can really help protect and enhance our soil resource and the future of food and farming," said Jess Davies, study co-author and Lancaster professor.

Just 7 percent of soil under conservation management had lifespans of less than 100 years, and almost half had lifespans of more than 5,000 years.

The best strategy for curbing erosion and replenishing soils is to reforest arable land, though researchers say other strategies that allow farming to continue can also boost soil health and longevity, including the use of cover crops.

Farmers can also help slow erosion rates by avoiding ploughing land down slope and employing hillside terracing when necessary, they said.

"It is clear that we have a conservation toolbox that can slow erosion and even grow soil," said John Quinton, study co-author and Lancaster professor. "Action is needed to promote the adoption of these measures so that we can protect and enhance our soil resource for future generations."