Brown tree snakes in Guam, water hyacinth in African rivers, rabbits in Australia, Burmese pythons in Florida—all these successful species have overrun their environments, heedlessly wiping out other creatures. Not one has voluntarily turned back. When the zebra mussels in the Hudson River began to run out of food, they did not stop reproducing. When fire ants relentlessly expand their range, no inner voices warn them to consider the future. Why should we expect Homo sapiens to fence itself in?
