The world grows 95% of its food in the uppermost layer of soil, making topsoil one of the most important components of our food system. But thanks to conventional farming practices, nearly half of the most productive soil has disappeared in the world in the last 150 years, threatening crop yields and contributing to nutrient pollution, dead zones and erosion. In the US alone, soil on cropland is eroding 10 times faster than it can be replenished.