Abstract: Climate change is already having adverse effects on animal life, and those effects are likely to prove devastating in the future. Nonetheless, the relevant harms to animals have yet to become a serious part of the analysis of climate change policy. Even if animals and species are valued solely by reference to human preferences, inclusion of their welfare dramatically increases the argument for aggressive responses to climate change. We estimate that, even under conservative assumptions about valuation, losses to nonhuman life might run into the hundreds of billions of dollars annually. Whatever the precise figure, the general conclusion is clear: An appreciation of the likely loss of animal life leads to a massive increase in the assessment of the overall damage and cost of climate change.