We continue our limited series, “A World Without”, with a discussion on the scarcity of healthy topsoil, vital to our global food supply. We’ll revisit a conversation we had with David Montgomery, a University of Washington professor, ecologist and geomorphologist. He says we must take drastic measures to preserve the world’s topsoil, necessary for a sustainable food supply. Montgomery was a MacArthur “Genius” fellow for “making fundamental contributions to our understanding of the geophysical forces that determine landscape evolution and of how our use of soils and rivers has shaped civilizations past and present.” He authored the books “Dirt: The Erosion of Civilizations”, which became a documentary, and “The Hidden Half of Nature: The Microbial Roots of Life and Health”. Montgomery’s latest book is “Growing a Revolution: Bringing Our Soil Back to Life”. He’ll also tell us why he believes we must “rethink the Green Revolution,”  to not only “feed the world,” but also to “nourish the world.”