Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future First Mediterranean Assessment Report (MAR1) Chapter 4 Ecosystems Coordinating Lead Authors: Mario V. Balzan (Malta), Abed El Rahman Hassoun (Lebanon) Lead Authors: Najet Aroua (Algeria), Virginie Baldy (France), Magda Bou Dagher (Lebanon), Cristina Branquinho (Portugal), Jean-Claude Dutay (France), Monia El Bour (Tunisia), Frédéric Médail (France), Meryem Mojtahid (Morocco/France), Alejandra Morán-Ordóñez (Spain), Pier Paolo Roggero (Italy), Sergio Rossi Heras (Italy), Bertrand Schatz (France), Ioannis N. Vogiatzakis (Cyprus), George N. Zaimes (Greece), Patrizia Ziveri (Spain) Contributing Authors: Marie Abboud-Abi Saab (Lebanon), Aitor Ameztegui (Spain), Margaretha Breil (Italy), Thierry Gauquelin (France), llse R. Geijzendorffer (France), Aristeidis Koutroulis (Greece), Jürg Luterbacher (Germany), Moham- mad Merheb (Lebanon), Cesar Terrer Moreno (Spain), Marco Turco (Spain), Elena Xoplaki (Germany) This chapter should be cited as: Balzan MV, Hassoun AER, Aroua N, Baldy V, Bou Dagher M, Branquinho C, Du- tay J-C, El Bour M, Médail F, Mojtahid M, Morán-Ordóñez A, Roggero PP, Rossi Heras S, Schatz B, Vogiatzakis IN, Zaimes GN, Ziveri P 2020 Ecosystems. In: Climate and Environmental Change in the Mediterranean Basin – Current Situation and Risks for the Future. First Mediterranean Assessment Report [Cramer W, Guiot J, Marini K (eds.)] Union for the Mediterranean, Plan Bleu, UNEP/MAP, Marseille, France, 151pp, in press (Final text before page editing for print) 1 Table of Contents 4 Ecosystems ............................................................................................................................ 5 Executive summary ......................................................................................................................... 5 4.1 Marine ecosystems .................................................................................................................... 6 4.1.1 Current condition and past trends .................................................................................................... 6 4.1.1.1 Observed changes ..................................................................................................................... 6 Key habitats undergoing change ....................................................................................................... 8 Coralligenous ................................................................................................................................ 8 Deep sea ecosystems .................................................................................................................. 10 Planktonic ecosystems ................................................................................................................ 10 Large vertebrates ........................................................................................................................ 12 Changes in biodiversity ................................................................................................................... 14 4.1.1.2 Past changes ............................................................................................................................ 17 Response of marine ecosystems to past temperature changes ..................................................... 17 Response of marine ecosystems to past changes in stratification and ventilation ........................ 18 Response of marine ecosystems to past changes in productivity ................................................... 18 Response of marine ecosystems to past changes in pH .................................................................. 19 4.1.2 Projected vulnerabilities and risks .................................................................................................. 19 4.1.2.1 Projected impacts and risks ..................................................................................................... 19 Projected impacts on microbes ....................................................................................................... 20 Projected impacts on primary and secondary production .............................................................. 20 Projected impacts on macrobenthic and pelagic species ............................................................... 22 Corals .......................................................................................................................................... 22 Seagrass ...................................................................................................................................... 23 Mussels ....................................................................................................................................... 24 Jellyfish ........................................................................................................................................ 24 Winners and losers .......................................................................................................................... 24 4.1.2.2 Vulnerabilities .......................................................................................................................... 25 Climate-related vulnerabilities ........................................................................................................ 25 Anthropogenic vulnerabilities ......................................................................................................... 26 4.1.3 Adaptation ...................................................................................................................................... 26 4.1.3.1 Long-term monitoring and adaptation strategies ................................................................... 26 4.1.3.2 The role of Marine Protected Areas (MPAs) for adaptation ................................................... 27 4.1.3.3 Management of fisheries and adaptation ............................................................................... 28 4.1.3.4 Adaptation strategies for ocean warming and ocean acidification in the Mediterranean Sea 29 4.1.3.5 Regional observation networks as a tool for adaptation ........................................................ 30 4.2 Coastal ecosystems ................................................................................................................. 31 4.2.1 Current condition and past trends .................................................................................................. 31 4.2.1.1 Observed changes ................................................................................................................... 31 Natural Mediterranean habitats under severe degradation ........................................................... 31 Sandy beaches and sand dunes .................................................................................................. 32 Rocky coasts ................................................................................................................................ 33 Coastal wetlands ......................................................................................................................... 34 Seagrass meadows ...................................................................................................................... 34 Coastal lagoons and deltas ......................................................................................................... 35 Salt marshes ................................................................................................................................ 36 Coastal aquifers .......................................................................................................................... 37 Risks from non-indigenous species ................................................................................................. 37 Phytoplankton ............................................................................................................................. 37 Jellyfish ........................................................................................................................................ 38 Fish .............................................................................................................................................. 38 Plants .......................................................................................................................................... 39 Other non-indigenous species .................................................................................................... 39 4.2.1.2 Past changes ............................................................................................................................ 40 Response of coastal ecosystems to past changes in sea level ........................................................ 40 Response of coastal ecosystems to past climate variability ............................................................ 41 2 4.2.2 Projected vulnerabilities and risks .................................................................................................. 42 4.2.2.1 Projections and risks based on biological groups .................................................................... 42 Phytoplankton ................................................................................................................................. 42 Fish .................................................................................................................................................