As the world warms, many species of plant and animal will have to find new—often cooler—places to live. But things are trickier for sedentary marine creatures like snails, worms, and clams, according to a new study. It finds that in the Northwest Atlantic Ocean, many species are spawning earlier in the year, when currents take their larvae southward and into warmer waters—the wrong direction. For some of them, including the sand dollars beloved by beachcombers, this means their range is shrinking.