Article: Pinsky, M. L., Worm, B., Fogarty, M. J., Sarmiento, J. L., & Levin, S. A. (2013). Marine Taxa Track Local Climate Velocities. Science. DOI:10.1126/science.1239352
We expect marine species to respond to climate change by either adapting or changing geographical ranges. But observed shifts in marine species distributions are often difficult to decipher, spanning a wide array of directions and rates. Most hypotheses focus on biological differences amongst species to explain changing distributions. The authors of this paper explored climate velocities – or, isotherms moving through space and time – as an explanation for changing species distributions.
What is a climate velocity?
Good question. Imagine a time when you were in the ocean and felt a “warm spot.” As the minutes pass, this warm spot moves a little closer to shore, maybe even a little shallower in the water. That moving warm spot is similar to a climate velocity. It makes sense that marine species would follow climate velocities; this study was the first attempt to make a direct connection.
Survey data from nine regions along the continental shelves of North America covering four decades were compiled to assess 360 fish and invertebrate species groups. Climate velocities specific to each taxon were developed to account for irregular species distributions. Climate and taxa velocities were compared over latitude and depth.
Marine species followed climate velocities! 74% shifted latitude and 70% shifted depth in the same direction as climate velocity. And there was little to no lag between the shifting climate and species distributions. Species followed climate velocities almost in sync.
There was little evidence to indicate other factors influenced taxa velocities. However, species-specific characteristics might explain some of the speed of change, excluding direction. This study did not incorporate many of the faster moving species because they moved out of survey areas entirely. Even so, species characteristics explained just 1.3% of variation in speed whereas climate velocities explained 18%.
Other factors that might explain species distributions include biological characteristics such as life history and prey distribution. However, basic physiological limits to temperature would ultimately control shifting distributions.
Why should we care about the connections between climate changes and fish populations? The recently released International Panel of Climate Change report presented strong arguments for significant global climate changes within the next century. The report underlines a need to identify how global food supplies, including fisheries, will be affected by climate change. Marine species are different from terrestrial species in that there are fewer barriers to geographic distribution. Fish populations can rapidly respond to climate velocity whereas studies of terrestrial organisms indicate a lag between climate and species shifts. Rapid redistributions will present challenges for fisheries management to keep pace with commercial fish populations. Climate velocity forecasts may be a useful tool for future management approaches.