“Think Like a Mountain” is part of a series published by Penguin named “Green ideas”, 20 classics of the environmental movement. This text is extracted from “A Sand County Almanach” published in 1949 by Aldo Leopold, an ecologist, forester, and nature writer. He talks about America's wildlands, mainly souvenirs of his childhood and early adulthood. He is also the first to have described the idea of trophic cascades, indirect interactions that can destabilise whole ecosystems, like taking away a predator. Leopold observed that after taking away wolves from Yellowstone National Park, deer proliferated and ate woody species to the point where there were no more… which subsequently reduced the deer population because there was nothing left to eat. What is amazing about this text is that it is so up-to-date on what is happening now but was written 70 years ago. When are we going to understand ?