Depletion of soil accelerates, putting human security at risk: Scientists
“This could create political challenges and uncertainties,” said Amundson. “Morocco will soon be the largest source of phosphorous in the world, followed by China. These two countries will have a great deal of say in the distribution of those resources. Some people suggest we will see the emergence of a phosphorous cartel.”
Contributing to climate change
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.
But agriculture’s physical disruption of soil releases stored carbon into the atmosphere. Based on the area of land used for farming worldwide, 50 to 70 gigatons of carbon has been released into the atmosphere throughout human history, according to the paper. Proponents of sequestration, the long-term storage of carbon in soil, have argued that regaining this carbon will be a means to mitigate continuing fossil fuel emissions of the greenhouse gas.
“Carbon sequestration plans won’t make a dent in the amount of soil released by climate change,” countered Amundson. “The amount of carbon stored through sequestration would be tiny compared to the potential amount lost through global warming.”
Of particular concern are the large carbon stores in the soils in the planet’s polar regions. Researchers have found that temperatures are increasing at greater rates in the northern latitudes.
“Warming those areas is like filling your freezer with food, then pulling the plug and going on vacation,” said Amundson. “There will be a massive feast of bacteria feeding on the food as the plug gets pulled on the stored carbon in the frozen soil. Microbes are already starting the process of converting the carbon to CO2 and methane.”
Recycling soil nutrients
The release notes that the authors recognize the human reliance on farming and note that most of the Earth’s most productive soils are already in agricultural production. However, they argue for better management of the soils we rely upon.
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.
Amundson noted that it did not take too long to get people to start separating paper, glass and aluminum cans from their trash for recycling.
“We should be able to do this with soil,” said Amundson. “The nutrients lost can be captured, recycled and put back into the ground. We have the skillset to recycle a lot of nutrients, but the ultimate deciders are the people who create policy. It’s not a scientific problem. It’s a societal problem.”
— Read more in Ronald Amundson et al., “Soil and human security in the 21st century,” Science 348, no. 6235 (8 May 2015): 1261071 (DOI:10.1126/science.1261071)
