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Global soil erosion has reached levels that will endanger humanity’s ability to feed itself if nothing is done to lower it, a study warns.

“I don’t think we worry enough about conserving soil resources for the long term.”

Tim Benton, University of Leeds

The review, published in Science last week (7 May), says soils are being lost faster than they are being naturally produced in many parts of the world. In addition, there is increased pressure on farmland from non-food uses, such as crops being grown for biofuels, and there may be future shortages of rock phosphate, which is used to make fertiliser, it says.
“The increases in food production in the developed regions of the world are plateauing,” says Ronald Amundson, a soil scientist at the University of California, Berkeley, in the United States, and one author of the study. “There are opportunities to increase food production in underdeveloped nations, but this will require expenditures for fertilisers to bring their yields up to what the regions can potentially produce.”
The phosphorus needed to create fertiliser is mined. This raw material has risen in price recently, according to the paper, prompting worries about the availability of inorganic fertilisers for farmers in developing countries.
The paper’s authors say that, instead of relying solely on fertiliser to increase yields from conventional farming, more efficient food distribution and nutrient recycling are needed to end hunger — one of the UN’s proposed Sustainable Development Goals (SDGs).

Science soil degradation map.JPG
The degradation and loss of soil around the world
Soil erosion is caused by the overuse of land, deforestation, desertification and water runoff — all of which are, to some extent, caused by farming. The Science paper comes as many scientists worry that soil protection targets in the draft SDGs may be removed from the final list of goals.
Since January, which marked the start of the International Year of Soils, scientists have been calling for greater political focus on soil management.
Tim Benton, a population ecologist at the University of Leeds in the United Kingdom, says better soil management could go a long way towards producing enough food in the future.
“I don’t think we worry enough about conserving soil resources for the long term,” he says.
In traditional farming systems, food production can be increased by using various techniques to reduce soil erosion, says Rattan Lal, a soil scientist at The Ohio State University in the United States. For example, he says farmers can preserve their soils using agroforestry and by covering it with crop residues.
But it is a major decision to switch to such methods, he says, as these are more labour intensive and can be less economically efficient, considering many farmers use agriculture to meet household needs for feed, fodder and building materials.
According to Lal, around 500 million farmers worldwide depend on farms of less than two hectares. If soil management were included in the global agenda to address climate change and food shortages, much could be done to help the two billion ‘hidden hungry’, who are not eating enough nutrients in their food, he says.


Ronald Amundson and others Soil and human security in the 21st century (Science, 8 May 2015)