In celebration of World Population Day July 11th, we look at the world’s human population through the lens of conservation and physical ecology. Tom Butler has produced a visually powerful book in collaboration with The Population Institute to make his point. He is Editorial Projects Director of the Foundation for Deep Ecology and the president of the Northeast Wilderness Trust. A conservationist and writer, his books include Wildlands Philanthropy, Plundering Appalachia, Keeping the Wild, Energy: Over-Development and the Delusion of Endless Growth and now Overdevelopment, Overpopulation, Overshoot. Host Elena Klaver spoke with him by phone.