TEMPE, Ariz. — Even the microbes, it seems, may be on the move.

As the planet warms, scientists say, the range of many plants and animals will change, shifting to cooler climes closer to the poles or at higher elevations. Such changes have already been documented for hundreds of species, including American goldfinches, brown argus butterflies and red oaks.

But Ferran Garcia-Pichel, a microbiologist at Arizona State University, has found evidence that this type of climate change impact may occur even among the smallest organisms. Photosynthesizing microbes that colonize arid soils will shift across the Southwest, with more heat-tolerant species moving northward and upward as temperatures increase.

No one is certain what the effects will be, because little is known about the more heat-tolerant species. But the impact could be profound, given that the microbes, called cyanobacteria, play a critical role in desert and scrub environments.