The new century has begun with some of the lowest grain prices in recent memory. From an economist’s vantage point, this is a sure sign of excess production capacity. However, there may be more here than meets the economist’s eye. Natural scientists, many of whom have contributed to this volume, see something very different. They see reason to be concerned about such issues as the overplowing of land and the overpumping of aquifers. They look at sustainable production and see a worrisome fraction of world food output being produced with the unsustainable use of land and water