As the ocean warms, marine species relocate toward the poles
Since pre-industrial times, the world's oceans have warmed by an average of one degree Celsius (1°C). Now researchers report that those rising temperatures have led to widespread changes in the population sizes of marine species. The researchers found a general pattern of species having increasing numbers on their poleward sides and losses toward the equator.
"The main surprise is how pervasive the effects were," says senior author Martin Genner, an evolutionary ecologist at the University of Bristol. "We found the same trend across all groups of marine life we looked at, from plankton to marine invertebrates, and from fish to seabirds."
The new study builds on earlier evidence for a prevailing effect of climate change on the distributions, abundance, and seasonality of marine species. Based on those findings, Genner's team reasoned that marine species should be doing well at the leading (poleward) edge of their ranges but poorly at their trailing (equatorward) side. They also realized that existing databases of global species distributions could be used to test this hypothesis.
Based on a thorough search of available data in the literature, the researchers now report on a global analysis of abundance trends for 304 widely distributed marine species over the last century. The results show that -- just as predicted -- abundance increases have been most prominent where sampling has taken place at the poleward side of species ranges, while abundance declines have been most prominent where sampling has taken place at the equatorward side of species ranges.