By Dr Regan Early, senior lecturer and leader of the FABio research group at the University of Exeter, and MbyRes student Christophe Patterson.
The English Channel prevents many rockpool species "making the jump" from Europe to the UK, according to new research from ConScience members.
Photo © Christophe Patterson
As beach temperatures soar, we might imagine animals that live in European rock pools dreaming longingly of the cooler shores of Cornwall as a new home that will help them survive climate change. But will these critters be able to reach our shores? This is a question asked by @Christophe_Patt and @ReganEarly of the FABiogeography research group within ConScience
We studied the St Piran's hermit crab, which was named by viewers of BBC Springwatch. We realised that the hermit crab had managed to make the journey from its home on the continent across the English Channel. The crab had briefly made the UK home back in the 1960s but disappeared after the Torrey Canyon oil spill and old age reduced its population down to zero. However, the crab proved itself to be the comeback kid of the rock pool world and turned up again in 2016.
Photo © Christophe Patterson
We modeled the effects of ocean currents on the crab larval stage and found that the crab larvae almost certainly came from Brittany in northern France, carried to Cornwall by ocean currents. However, we found very few opportunities for this to happen. Only once in ten years were the currents suitable for the tiny St Piran's crab larvae to cross the Channel. Even on these currents, it takes a long time for larvae to be carried to the UK: much longer than most other species' larvae can survive. So, even with rare ocean currents capable of carrying larvae to the UK, many species will never make that journey. Crabs and other crustaceans have the best chance, as many have larvae that could survive the crossing, but other groups like sea snails, sponges and seaweed just don't live for long enough in open water to get here.
With sea temperatures expected to rise due to climate change, many rockpool species in south-west England may become threatened. Creatures from warmer waters to the south might be able to replace them, but our study suggests Channel currents mean many animals and plants cannot survive the crossing. So the richness of intertidal wildlife in the UK could decrease.
Photo © Christophe Patterson
Rockpool animals are not alone in this quest to find new habitat. As the world warms, many species will find themselves living in environments that are too hot for them to survive. To avoid extinction, species must move to new areas, keeping them within their preferred climate. However, physical barriers like the English Channel may prevent species from doing this. We’re continuing to study how wildlife is shifting around the world, and come up with conservation solutions that can help species threatened by climate change.
The paper, published in the journal Marine Biology, is entitled: "The range expansion of Clibanarius erythropus to the UK suggests that other range-shifting intertidal species may not follow."
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