Habitat conservation can help buy time for heat-sensitive species in the face of climate change – but it might also leave them in a trap by preventing them from adapting in time, according to a study from the UC Davis Bodega Marine Laboratory published late last year in the journal Ecology.

Plants and animals form habitats that alter the climate within them. Just as a forest can feel cool on a hot day, a bed of mussels creates a microclimate with lower temperatures and higher humidity than exposed rock. That can be especially important on the seashore, where plants and animals have to survive rapidly changing conditions as tides rise and fall.

Laura Jurgens, a graduate student at the Bodega lab at the time of the study, Professor Brian Gaylord of the UC Davis Department of Evolution and Ecology and Lauren Ashlock, University of Vermont, investigated how this “ecological air conditioning” affects the survival of shoreline species.

Intact mussel beds are highly effective in buffering against outside conditions, they found. Conditions remained stable throughout the day with lower temperatures and higher humidity than outside the bed.

Importance of protecting mussel beds

They then studied two common animals, porcelain crabs (Petrolisthes cinctipes) and the isopod Cirolana harfordi (a marine version of a pill bug) and their survival in intact mussel beds and in patches of rock cleared of mussels.

“Without the protection of mussel beds, we found that they cannot survive even present-day conditions,” Jurgens said. But they can tolerate a worse-case climate scenario for the end of this century, as long as the mussel bed remained intact, she said.

“This research shows that it's more important than ever to protect vulnerable habitats like mussel beds, which are threatened by trampling and mussel harvest in many coastal areas of the U.S.” Jurgens said.

The study does also raise the question of whether a climate refuge could become an evolutionary trap. When a refuge finally does collapse, the species within might not be able to adapt to changed conditions outside.

Jurgens is now an assistant professor at Texas A&M University, Galveston. The work was supported by a grant from the National Science Foundation.