Predict how marine animals will respond to climate change


Sea urchins, like this one, have moved to Tasmania in response to climate change. (Photo: Rick Stuart-Smith)

As the world has warmed in recent decades, scientists have recorded species of fish, butterflies and bumblebees moving to new home ranges, apparently in search of cooler temperatures. Yet it is still difficult for scientists to predict exactly which species will move in response to global warming, and how far they will go. After all, it’s not like an entire ecosystem is moving north or south at once; some members leave and others stay, creating a new dynamic between the migrants and the animals they encounter upon arrival at their new destination. Now, however, a new study offers a step towards such a prediction, at least for marine animals.

In a study published this week in the journal Ecology letters, a team of scientists from Canada, Australia and the United Kingdom have identified traits common to certain species of marine animals that have extended their range further to the poles in colder waters. It’s a step towards predicting which other animals will move in response to climate change. If such predictions improve in the future, governments and other groups could better prepare for a myriad of changes, including a sudden emergence of commercially fishable fish in a country’s waters. Such changes can plunge industries into “chaos,” says Jennifer Sunday, lead author of the study and zoological researcher at the University of British Columbia. “Instead of having a Wild West, why don’t we watch this change and think about how to help fishermen move from one resource to another?

Species that originally lived in a large north-south expanse along the shore were more likely to push the envelope of their place of residence even further.

Sunday and his colleagues analyzed home range data for 104 species of fish and invertebrates living off the coast of southeastern Australia. Using data from multiple points in time, they were able to see which home ranges changed and by how much. From this data, scientists gleaned which traits are common to marine animals that extend their range the most.

Species that originally lived in a large north-south expanse along the shore were more likely to push the envelope of their place of residence even further, the authors found. Researchers believe this is because species with large ranges are likely generalists who are better equipped to deal with new habitats. Being able to swim – not just crawl, or worse, not move at all – helps. The same goes for being omnivorous, as opposed to being carnivorous or herbivorous.

These traits are just a starting point. Scientists have yet to answer big questions before they can predict exactly which animals are coming and going in a region when it warms up. They will need to check whether the characteristics that make marine animals mobile in Southeast Australia also apply elsewhere in the world. Plus, the debate continues over which traits really matter – a previous study found that characteristics like, say, what fish ate didn’t explain their movement as much as simple water temperature.

Meanwhile, in Southeast Australia, climate change is already affecting lobster fishermen. Warming waters have drawn sea urchins to the ocean floor around Tasmania, where they have eaten so much kelp that there is not enough left to support the region’s large lobster population. Due to the unique dynamics of the water currents there, the sea in Southeast Australia has actually warmed three to four times faster than average. “Because it’s happening so much faster here, it’s a window into what could be happening everywhere, a little bit more down the line,” Sunday said.

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