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Creating Resilience: Trophic Cascades and Climate Change

Ecologist Robert Paine summed up the effects of keystone predator removal by saying, “You can change the nature of the world pretty simply. All you need to do is remove one species.” In The Wolf’s Tooth, I compare ecosystems from which carnivores have been removed to a game of Jenga. This game involves removing wooden blocks one at a time from a tower without causing it to collapse. As you remove them, the tower starts to teeter, loosening some of the blocks, making them easier to remove. Eventually the whole system collapses. In an ecological game of Jenga in an aspen forest, you might begin by removing species that may seem redundant. If you remove the black-capped chickadees first, not much happens, the system continues functioning more or less as usual. The number of chestnut-backed chickadees increases to fill the gap left by the black-caps. If you remove short-tailed weasels next, the mouse population initially increases, but then the coyotes start eating the surplus mice, as do the northern harriers, and mouse numbers go back down to the level they were at before you removed the weasels. A casual observer might not notice much missing. If you continue by removing white-tailed deer, the other ungulate species carry on, filling in the gap by producing more elk and moose. . . .Read more »