Warmer climate squeezes aquatic predators out of their preferred habitat.

Ecosystems are mosaics of different habitats, each of which provides its own opportunities and risks to the organisms that inhabit it. The profitability of any habitat depends on a variety of biotic and abiotic variables including the abundance of prey, vulnerability to predators, and physical features such as temperature that modify physiology and behavior. Because biological and physical conditions are continuously varying, and it is rare that any single habitat satisfies all requirements for successfully completing life cycles, organisms must navigate across habitat landscapes to fulfill their resource needs. Human modifications to habitats are presenting new challenges to many organisms. One underappreciated effect humans are having on the profitability of landscapes is via climate warming, where we are changing the rules of the game controlling how consumers can move among habitats. In PNAS, Guzzo et al. (1) show that warmer water temperatures in lakes restrict the daily movements of a top predator between habitats that are profitable for feeding and those that provide cold water for maintaining physiological functions. Intensified thermal barriers to movement under warmer climate conditions reduce feeding rates in productive habitats, thereby slowing growth of the predator. Surprising stories such as this continue to emerge from field ecology and serve as a sharp reminder that human perturbations to the Earth’s climate system have many untold consequences for the biosphere.