Kahn has done extensive cross-cultural studies of children’s values and attitudes about open space and animal life and forests and plants and water—and the degradation and disappearance of all these things. He believes that, with every generation, kids are lowering their knowledge and expectations for what is a normal interaction with nature—creating a kind of generational amnesia about the natural world. If nature is indeed a source of mental and emotional replenishment, this could emerge as one of the most compelling psychological issues of the not-so-faraway future.