Human security at risk as depletion of soil accelerates

Sarah Yang at the UC Berkeley News Center: Steadily and alarmingly, humans have been depleting Earth’s soil resources faster than the nutrients can be replenished. If this trajectory does not change, soil erosion, combined with the effects of climate change, will present a huge risk to global food security over the next century, warns a review paper authored by some of the top soil scientists in the country.

The paper singles out farming, which accelerates erosion and nutrient removal, as the primary game changer in soil health. “Ever since humans developed agriculture, we’ve been transforming the planet and throwing the soil’s nutrient cycle out of balance,” said the paper’s lead author, Ronald Amundson, a UC Berkeley professor of environmental science, policy and management. “Because the changes happen slowly, often taking two to three generations to be noticed, people are not cognizant of the geological transformation taking place.”

In the paper, published [May 7] in the journal Science, the authors say that soil erosion has accelerated since the industrial revolution, and we’re now entering a period when the ability of soil, “the living epidermis of the planet,” to support the growth of our food supply is plateauing. The publication comes nearly two weeks ahead of the Global Soil Security Symposium at Texas A&M University, a meeting held as part of the declaration of 2015 as the International Year of Soils by the United Nations.

The authors identify the supply of fertilizer as one of the key threats to future soil security. Farmers use three essential nutrients to fertilize their crops: nitrogen, potassium and phosphorous. The paper credits the discovery of synthetic nitrogen production in the early 1900s for significantly increasing crop yields, which in turn supported dramatic growths in global population. Because the process of synthesizing nitrogen is energy-intensive, its supply is dependent on fossil fuels.

...Another threat to soil security relates to its role as a mass reservoir for carbon. Left unperturbed, soil can hold onto its stores of carbon for hundreds to thousands of years. The most recent estimates suggest that up to 2,300 gigatons of carbon are stored in the top three meters of the Earth’s soil – more carbon than in all the world’s plants and atmosphere combined. One gigaton is equal to a billion tons.

...One proposal is to stop discarding nutrients captured in waste treatment facilities. Currently, phosphorous and potassium are concentrated into solid waste rather than cycled back into the soil. Additionally, more efficient management is needed to curtail losses from soil. Excess nitrogen, for example, is considered a pollutant, with the runoff sapping oxygen from the nation’s waterways, suffocating aquatic life and creating dead zones in coastal margins...

A South Korean combine in 1976