Could the world’s supply of fertile soil really run out? That’s the question posed by TIME Magazine in a recent Q & A with University of Sydney professor John Crawford, and as far-fetched as the premise may sound, it turns out that soil erosion and degradation is a very serious issue. According to Crawford, we have just about 60 years of good soil left at current erosion rates due to farming methods that strip the soil of nutrients, which could lead to a serious food crisis in the mid-21st century as the world population continues to grow.

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Unsustainable farming methods are currently stripping the topsoil of nutrients at 10 to 40 times the rate that it can be naturally replenished, Crawford told TIME, which could create real problems for the world’s farmers and food supplies. “Simply put, we take too much from the soil and don’t put enough back,” Crawford explained. “Whereas the classic approach would have been to leave stubble in the field after harvest, this is now often being burnt off, which can make it easier to grow the next crop, or it’s being removed and used for animal feed.”

Soil fertility isn’t the only problem, though. Soil stores carbon, and recent studies have shown that over-plowing can cause the release of greenhouse gasses. Carbon content is part of what gives soil its fertility; resting soil and growing cover crops can help to replace carbon in soil, but it can take decades to build up the carbon content of soil.

Water scarcity is another problem that farmers will face in coming decades. Depleted topsoil doesn’t hold water as well as fertile soil, and as a result, water just runs through it, requiring more irrigation to keep plants properly watered. As the world’s fresh water supplies are stretched, this will be another major challenge for farmers to face.

To reverse these trends, Crawford recommends putting a stop to farming practices like tillage and over-grazing, and adding things like human waste to the soil as fertilizer. “We need to recognise that this is a global problem that would benefit from a global approach,” Crawford says. “We don’t need to reinvent the wheel in each country, and we don’t have time to do so. It takes decades to regenerate soil.”

via TIME