Impacts of climate change on intertidal habitats, relevant to the coastal and marine environment around the UK

The lack of dramatic observed responses of intertidal species from 2002 to 2018 is consistent with the lack of increase in sea temperatures since 2000. Despite the continued global upward trend in temperature, UK regional sea temperatures have remained stable or declined over the same period, with only those in western Scotland increasing. This hiatus followed a period of rapid warming from 1980 to 2000 when many range shifts occurred. • Short-term fluctuations in abundance of climate-sensitive species have continued through the mid-2010s, and most of these changes in abundance are consistent with changes in temperature at timescales of less than a decade, offering further evidence for the continued sensitivity of intertidal species to climate. • Leading range edges of Lusitanian topshells are continuing to move northwards in North Wales and south-east England. The Community Temperature Index (CTI) shows considerable promise for use as a measure of the combined response of multiple species to climate change. Preliminary analysis of spatial patterns in UK rocky shore communities shows that the CTI follows temperature closely, and that changes in sea-surface temperature over time are matched by changes in CTI. • The lack of an upward trend in UK sea temperatures is unlikely to continue, since longer-term trends appear to be less regionalised than short-term ones, and further changes are likely to be more dramatic in the next decade as local temperatures catch up with global trends. • A heatwave event in summer 2018 caused heat damage to the high and midshore fucoids in UK regional seas