Climate change is the greatest threat to humanity and our planet as we know it. Turtles and tortoises are a perfect bellwether for the crisis as many aspects of their biology are directly influenced by their environment. Already, their populations are being affected, because their sex is determined by temperatures during egg incubation. If all hatchlings develop into females, reproduction will eventually cease to occur. Changing weather patterns are also accelerating loss of suitable habitat for many species to survive. The combined pressure of these changes to the environment could be catastrophic for turtles and tortoise species, of which more than half are threatened with extinction.