HIGHLY SENSITIVE MAMMALS, PANDAS START TO OVERHEAT AT TEMPERATURES of just 77 degrees. As climate change drives the mercury higher, they run out of cool mountainside refuges to chill in. Forced to climb ever higher for relief, Central China’s roughly 1,800 wild pandas might eventually have to move beyond their only source of food. Pandas evolved to rely on nutrition-poor bamboo, and can only digest a tiny portion of the quantity that they eat. So to survive, they chow down on around 30 pounds of the plant each day. But bamboo forests are slow-growing and not likely to migrate with the pandas—dooming them to a hot or hungry future.