IMPACTS OF CLIMATE CHANGE ON INTERTIDAL SPECIES

Steve Hawkins
Marine Biological Association, Plymouth

Executive Summary

There is strong evidence that recent rapid climate change has resulted in changes in the abundance and distribution of southern, warm-water species that reach their northerly limit on rocky shores in the UK. Significant extensions in range have occurred since the mid 1980s with further species range extensions observed over the shorter time period of the MarClim project (2001-2005). Between 2002 and 2004 a number of these species increased their range around N. Scotland (moving clockwise around the coast and into the colder North Sea) and also eastwards along the English Channel. These range extensions were not trimmed back by the recent cold winter of 2005/06 (the coldest since 1995/96 for England and Wales, and since 2000/01 for Scotland and Northern Ireland). Decreases in the abundance of northern, cold-water species that reach their southern limit in northern Europe have been observed; however, there is less evidence on rocky shores of northern cold-water species retreating northwards.

These observed shifts in distribution match those predicted by climate change models based on increases in Sea Surface Temperature (SST). However, there are also other climate-related factors which may be important such as new habitat being made available for rocky shore species along the south coast of the UK as a result of the proliferation of sea defences in response to rising sea levels and stormier seas. This facilitates the spread of species eastwards along the coast in response to warmer temperatures by the breakwaters acting as ‘stepping stones’ to reach rocky shores further east. More research is needed into this combination of factors and on the precise way species are affected by temperature (e.g. are adults or juveniles more sensitive? Is air temperature as important as SST?) 

Level of Confidence

MEDIUM

Overall, we have a medium level of confidence that climate is affecting the distribution of species

This is based on the fact that there is a large amount of good quality data from time series from a wide spatial extent and covering long time periods (see supporting evidence). Also, the modelling so far undertaken has accurately represented past and present observed distributions using changes in climate variables. However, we can only increase our confidence if future monitoring is carried out to validate model forecasts and if surveys are undertaken to increase the amount of baseline data for areas such as the east coasts of Scotland and England. Also, rates of change are increasing so the observations need to be more frequent to take this into account, and reversals may occur in the future due to cold winters. Further investigation is also required into the mechanisms influencing species distribution and abundance and influence of factors other than temperature, such as artificial structures.

Key sources of Information

The source for this information is the Marine Biodiversity and Climate Change Project (MarClim) which ran between 2001 and 2005 and is now being continued under the umbrella of the MECN (MECN 2006). All reports and papers, including those containing details of the MarClim model outputs, are available at http://www.mba.ac.uk/marclim/marclim.php?sec=pub (MarClim undated a).

Information on the recent cold winter was provided by the Met Office and a summary can be found at http://www.metoffice.com/corporate/pressoffice/2006/pr20060303b.html (Met Office 2006). 

Please acknowledge this document as: Hawkins, S. (2006). Impacts of Climate Change on Intertidal Species in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk