Background
The authors report that "although most studies of climate change effects on corals have focused on temperature-induced coral bleaching in tropical areas, poleward range shifts and/or expansions may also occur in temperate areas, as suggested by geological records and present-day eyewitnesses in several localities," citing the work of Greenstein and Pandolfi (2008) and Precht and Aronson (2004).

What was done
To further explore this subject, Yamano et al. collected records of coral species occurrence from eight temperate regions of Japan along a latitudinal gradient," where they obtained what they describe as "the first large-scale evidence of the poleward range expansion of modern corals, based on 80 years of national records ... where century-long measurements of in situ sea-surface temperatures have shown statistically significant rises."

What was learned
The three researchers determined that "four major coral species categories, including two key species for reef formation in tropical areas, showed poleward range expansions since the 1930s, whereas no species demonstrated southward range shrinkage or local extinction," adding that "the speed of these expansions reached up to 14 km per year," which they say "is far greater than that for other species." And they further note that "in regions with poleward current flows (east coast of the United States [Precht and Aronson, 2004], east coast of South America, east coast of Africa and east coast of Australia [Figueira and Booth, 2010]) the speed would be much greater."

What it means
The Japanese scientists conclude that their results, "in combination with recent findings suggesting range expansions of tropical coral-reef associated organisms, strongly suggest that rapid, fundamental modifications of temperate coastal ecosystems could be in progress." And in light of these facts they opine that "temperate areas may serve as refugia for tropical corals in an era of global warming."

References
Figueira, W.F. and Booth, D.J. 2010. Increasing ocean temperatures allow tropical fishes to survive overwinter in temperate waters. Global Change Biology 16: 506-516.

Greenstein, B.J. and Pandolfi, J.M. 2008. Escaping the heat: Range shifts of reef coral taxa in coastal Western Australia. Global Change Biology 14: 10.1111/j.1365-2486.2007.01506.x.

Precht, W.F. and Aronson, R.B. 2004. Climate flickers and range shifts of reef corals. Frontiers in Ecology and the Environment 2: 307-314.