Climate change impacts on corals in the UK Overseas Territories of British Indian Ocean Territory (BIOT) and the Pitcairn Islands Blue Belt Programme April 2021 Authors: Lincoln, S., Cowburn, B., Howes, E., Birchenough, S.N.R., Pinnegar, J., Dye, S., Buckley, P., Engelhard, G.H. and Townhill, B.L. Issue date: 29 March 2021 © Crown copyright 2020 This information is licensed under the Open Government Licence v3.0. To view this licence, visit www.nationalarchives.gov.uk/doc/open-government-licence/ This publication is available at www.gov.uk/government/publications www.cefas.co.uk Document Control Submitted to: Kylie Bamford (UK Foreign, Commonwealth and Development Office) Date submitted: 29 March 2021 Project Manager: Victoria Young Report compiled by: Susana Lincoln Quality control by: Georg H. Engelhard Approved by and date: Christopher Darby and Silvana Birchenough, 25 March 2021 Version: Final checked Version Control History Author Date Summary of changes Version Lincoln et al. November 2020 Initial draft V0.1 Lincoln et al. January 2021 External peer review completed V0.2 Lincoln et al. February 2021 QC QA corrections and final draft V1.0 Lincoln et al. February 2021 Comments from Emily Hardman V1.1 (Marine Management Organisation) Lincoln et al. March 2021 Editorial comments from Silvana V2.0 Birchenough et al. Lincoln et al. March 2021 Editorial comments from V2.1 Christopher Darby Lincoln et al. March 2021 All comments addressed Final Lincoln et al. April 2021 Final checks by reviewers prior Checked to publication This report has been reviewed by: Sheppard, C. (University of Warwick, UK), Wabnitz, C. (University of British Columbia, Canada), Dutra, L. (CSIRO, Australia), Graham, J. (Cefas, UK), Archer-Rand, S. (Cefas, UK) and Emily Hardman (MMO, UK). Recommended citation for this report: Lincoln, S., Cowburn, B., Howes, E., Birchenough, S.N.R., Pinnegar, J., Dye, S., Buckley, P., Engelhard, G.H. and Townhill, B.L. (2021). Climate change impacts on corals in the UK Overseas Territories of BIOT and the Pitcairn Islands. Scientific Report. UK Blue Belt Programme, 83 pp. Contents 1. Executive summary ................................................................................................................. 1 2. Introduction ............................................................................................................................. 2 2.1. Purpose of this document ................................................................................................ 2 2.2. Background to this document .......................................................................................... 2 2.3. British Indian Ocean Territory (BIOT) ............................................................................... 3 2.4. Pitcairn Islands ................................................................................................................ 4 2.5. Overview of marine climate change in the Indian and Pacific Ocean regions ................... 5 2.5.1. Sea surface temperature change ............................................................................. 5 2.5.2. Ocean acidification and carbon chemistry ................................................................ 7 2.5.3. Sea level rise ......................................................................................................... 10 2.5.4. Extreme weather events ........................................................................................ 11 2.6. Overview of climate change impacts on corals .............................................................. 12 2.6.1. Impacts from bleaching .......................................................................................... 12 2.6.2. Impacts from changes in carbon chemistry and ocean acidification ....................... 13 2.6.3. Impacts from sea level rise and extreme weather events ....................................... 15 3. BIOT: drivers of marine climate change................................................................................. 17 3.1. Sea surface temperature change ................................................................................... 17 3.1.1. Observed changes ................................................................................................. 17 3.1.3. Projected future changes ....................................................................................... 19 3.2. Ocean acidification and carbon chemistry...................................................................... 21 3.2.1. Observed changes ................................................................................................. 21 3.2.2. Projected future changes ....................................................................................... 22 3.3. Sea level rise ................................................................................................................. 23 3.3.1. Observed changes ................................................................................................. 23 3.3.2. Projected future changes ....................................................................................... 24 3.4. Extreme weather events ................................................................................................ 24 3.4.1. Observed changes ................................................................................................. 24 3.4.2. Projected future changes ....................................................................................... 25 4. BIOT corals: climate change impacts .................................................................................... 26 4.1. Impacts from bleaching.................................................................................................. 26 4.1.1. Observed impacts .................................................................................................. 26 4.1.2. Projected future impacts ........................................................................................ 27 4.1.3. Knowledge gaps and research needs .................................................................... 28 4.2. Impacts from changes in carbon chemistry and ocean acidification ............................... 28 4.2.1. Observed impacts .................................................................................................. 28 4.2.2. Projected future impacts ........................................................................................ 29 4.2.3. Knowledge gaps and research needs .................................................................... 29 4.3. Impacts from sea level rise and extreme weather events ............................................... 30 4.3.1. Observed impacts .................................................................................................. 30 4.3.2. Projected future impacts ........................................................................................ 30 4.3.3. Knowledge gaps and research needs .................................................................... 31 4.4. Other anthropogenic pressures ..................................................................................... 31 4.4.1. Knowledge gaps and research needs .................................................................... 32 5. Pitcairn Islands: drivers of marine climate change ................................................................. 33 5.1. Sea surface temperature change ................................................................................... 33 5.1.1. Observed changes ................................................................................................. 33 5.1.2. Projected future changes ....................................................................................... 35 5.2. Ocean acidification and carbon chemistry...................................................................... 36 5.2.1. Observed changes ................................................................................................. 36 5.2.2. Projected future changes ....................................................................................... 36 5.3. Sea level rise ................................................................................................................. 37 5.3.1. Observed changes ................................................................................................. 37 5.3.2. Projected future changes ....................................................................................... 38 5.4. Extreme weather events ................................................................................................ 38 5.4.1. Observed changes ................................................................................................. 38 5.4.2. Projected future changes ....................................................................................... 39 6. Pitcairn Islands corals: climate change impacts ..................................................................... 40 6.1. Impacts from bleaching.................................................................................................. 40 6.1.1. Observed impacts .................................................................................................. 40 6.1.2. Projected future impacts ........................................................................................ 41 6.1.3. Knowledge gaps and research needs ...................................................................