Post Carbon Fellow Bill Ryerson was quoted in this article on threats to agriculture.

From the article:

William Ryerson, founder and president of the Population Media Center and Chair and CEO of the Population Institute, is also very concerned about fertilizers’ impact on soil. He has questioned how, in the long run, this will impact agriculture.

“The world’s agricultural systems rely substantially on increasing use of fertilizers,” Ryerson told Truthout. “But now, the world’s farmers are witnessing signs of a declining response curve, where the use of additional fertilizer yields little additional food product.”

According to Ryerson and many farmers Truthout has spoken with, fertilizers and intensive crop planting lower the quality of soil. These factors will increasingly limit the possibilities of raising food production substantially and will, at a minimum, boost relative food prices and cause hunger for increasing numbers of people around the world.