THE IMPACT OF CLIMATE CHANGE ON SUBTIDAL AND INTERTIDAL BENTHIC SPECIES IN SCOTLAND Report to Scottish Natural Heritage from the Marine Biological Association of the UK Keith Hiscock Alan Southward Ian Tittley Adam Jory & Stephen Hawkins January 2001 THE IMPACT OF CLIMATE CHANGE ON SUBTIDAL AND INTERTIDAL BENTHIC SPECIES IN SCOTLAND Contents Contents .................................................................................................................................. i List of Figures and Tables ................................................................................................... iii ABSTRACT ............................................................................................................................. v 1. INTRODUCTION........................................................................................................... 1 1.1 Species and biotopes in Scotland ........................................................................ 1 1.2 Current climate – seawater temperatures ....................................................... 1 1.3 Past climates...................................................................................................... 1 1.5 Establishing recent effects of climate change in north-east Atlantic waters – finding baselines............................................................................................. 5 1.6 Evidence for effects of change in species due to seawater warming elsewhere ......................................................................................................... 10 2. SPECIES AND BIOTOPES TO BE RESEARCHED .................................................. 10 2.1 Species and biotopes included in statutes, directives and Biodiversity Action Plans ..................................................................................................... 10 2.2 Species and biotopes with a restricted distribution in Scotland ................ 10 2.3 Selecting species and biotopes to be included in assessment .................. 13 3. LITERATURE REVIEW - CURRENT DISTRIBUTIONS ............................................ 14 3.1 The sources and nature of distributional records ........................................ 14 4. KEY ENVIRONMENTAL FACTORS THAT DEFINE DISTRIBUTIONAL RANGE.... 14 4.1 Presence of suitable habitats ......................................................................... 14 4.2 Temperature ..................................................................................................... 14 4.3 Hydrographical conditions - direction of currents ....................................... 15 4.4 Geographic barriers......................................................................................... 16 4.5 Water ‘quality’ .................................................................................................. 16 5. LIKELY EFFECTS OF CLIMATE CHANGE ON MARINE ECOSYSTEMS............... 16 6. MECHANISMS OF CLIMATE CHANGE EFFECTS................................................... 17 7. LIKELY EFFECTS OF CLIMATE CHANGE ON SPECIES ....................................... 18 7.1 Introduction...................................................................................................... 18 7.2 Effects of increase in air temperatures on open shore species.................. 19 7.3 Effects of increased air temperatures on species in enclosed waters....... 19 i 7.4 Effects of increased air temperatures on surface waters and intertidal isolated water bodies (rockpools).................................................................. 19 7.5 Effects of increase in seawater temperatures............................................... 20 7.6 Biotic interactions............................................................................................ 20 8. DEVELOPING A ‘RULE BASED’ SYSTEM FOR ASSESSING LIKELY EFFECTS FOR A PARTICULAR SPECIES ................................................................................ 21 8.1 Components..................................................................................................... 21 8.2 Mechanisms - effects for southern species in a temperature rise scenario22 8.3 Mechanisms - effects for northern species in a temperature rise scenario22 8.4 Mechanisms – the importance of residual currents. .................................... 23 8.5 Exceptions - localised effects in isolated waters ......................................... 23 8.6 The ‘key’ - determining the likely effects of temperature increase on a particular species ............................................................................................ 23 9. EXAMPLES OF POSSIBLE CHANGE....................................................................... 26 9.1 Likely effects on representative species....................................................... 26 9.2 Likely effects on susceptible biotopes.......................................................... 27 10. LOCATIONS WHERE CHANGE MIGHT BE PARTICULARLY ACUTE ................... 27 11. RELEVANCE TO SCOTTISH SACs .......................................................................... 28 12. RECOMMENDATIONS FOR FUTURE ACTION BY SNH ......................................... 29 13. REFERENCES AND BIBLIOGRAPHY OF RELEVANT LITERATURE .................... 32 APPENDICES........................................................................................................................ 41 Appendix 1. Information on species distributions from A.J. Southward and S.J. Hawkins ............................................................................................................ 41 Appendix 2. Benthic marine species which occur in Scotland or may spread there or be affected by expected climate change and which are listed in statutes, directives or Biodiversity Action Plans. ........................................ 45 Appendix 3. Benthic biotopes which are part of Biodiversity Action Plans (BAPs) and are either found in Scotland or are likely to spread there in response to expected climate change........................................................... 47 Appendix 4. Species with climatically restricted distributions or abundance in or near Scotland ................................................................................................... 51 Appendix 5. Basic information for species with a limited geographical range in or near Scotland whose distribution might change due to global warming.61 Appendix 6. Detailed information sheets for biotopes that are part of Biodiversity Action Plans or that may change in distribution as a result of climate change............................................................................................... 127 Appendix 7. Predictions of climate change (temperature rise) for selected representative species. ................................................................................. 155 ii List of Figures and Tables Figure 1: Recent mean seawater temperatures around Britain for summer (top) and winter (bottom). (From Hiscock, 1998, re-drawn from Lee & Ramster, 1981.).......................... 2 Figure 2: Long-term change. Oceanographic and palaeoceanographic maps of the northeast Atlantic depicting inferred surface currents and ecologic water masses. (After Ruddiman & McIntyre, 1976.). ......................................................................................... 3 Figure 3: Global surface temperatures (combined land, air & sea temperatures) from 1840 to 1999. (From: http://www.meto.govt.uk/sec5/CR_div/GlobeTemp.) © Crown Copyright…………………………………………………………………………………………4 Figure 4: Global temperature rise due to increase in greenhouse gases. Predicted changes in (from upper to lower lines) land, global, sea and ‘unperturbed’. (From: http://www.meto.govt.uk/sec5/CR_div/Brochure98/index.html.) © Crown Copyright……4 Figure 5: Biogeographical characteristics of the coast of the British Isles including the range limits of some species. From Forbes (1858)………………………………………………..6 Figure 6: The direction of near-surface residual currents around the British Isles. (From Hiscock, 1998, re-drawn from Lee & Ramster, 1981)……………………………………..15 Figure 7: Water currents and quality decision tree for southern species…………………….26 Figure 8: Location of proposed and candidate SACs in Scotland (map supplied by SNH, square brackets added to indicate sites without seabed habitats)………………………28 Table 1: Northern and southern species with good distributional records that are considered to have climatically restricted distributions in or near Scotland………………………….11 Table 2. Biotopes with good distributional records that are considered to have climatically restricted distributions in or near Scotland and that might be affected by climate change. * = Biotopes for which more detailed information is given in Appendix 6………………12 Table 3. Initial proposed list of locations around the Scottish coast that could be targeted for establishing a baseline and recording change in species abundance and presence in relation to climate change. Sites that are known to be in proposed or candidate SACs are emboldened………………………………………………………………………………30 iii iv THE IMPACT OF CLIMATE CHANGE ON SUBTIDAL AND INTERTIDAL BENTHIC SPECIES IN SCOTLAND ABSTRACT Keywords: Climate change; seabed wildlife; species distribution. 1. SNH require to know what impact climate change might currently be having and what effect it might have in the future on seabed wildlife around the coast of Scotland. 2. The marine flora and fauna of Scottish waters, excluding bacteria,