[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]
We may be running out of dirt. The intensive farming of recorded history, accelerated by the last several decades of industrial agriculture, now strips the soil of some 20 tons of dark, rich organic matter per hectare per year.
That's not just a problem for farmers, much of that carbon ends up in the atmosphere, contributing to climate change, which then goes on to exacerbate other food-growing issues such as drought or floods and extreme temperatures. Plus, degraded soils spur farmers to clear yet more land, contributing to the rapid destruction of the world's forests, further exacerbating climate change.
So the future of farming is, in large part, a future of fighting climate change—and battling to preserve soils.
Fortunately, there are several promising methods. No-till farming, in which soil is left undisturbed by plows, can help restore some 600 to 900 megatonnes of carbon to the earth over several decades.
And organic matter can be put back into the soil more directly, via a method known as biochar. Basically, waste plant matter is burned into charcoal and then added to the soil. In addition to keeping carbon out of the atmosphere, such biochar may also improve fertility, though it probably can't be practiced on a global scale.
Ultimately, the future of farming will also be decided by the future of eating: the amount of land needed for farming in the first place could be radically reduced if people stopped eating as much meat.