While the impact of climate change at global level has been widely studied, its form and extent in the Mediterranean remains vague. Climate change is likely to have drastic effects on the habitat of the Mediterranean flora and fauna, but its impacts will vary between Mediterranean regions and between marine protected areas (MPAs) within each region. The IUCN has produced a guide which analyzes the threats and effects of climate change on Mediterranean marine biodiversity and provides MPA managers with tools to monitor and mitigate changes in their own MPAs.
This new IUCN publication provides a clear and synthetic summary of the main effects of climate change observed to date on Mediterranean marine biodiversity, according to existing research. It also outlines the many uncertainties that still exist in understanding ecological responses to climate change. The report was prepared by the IUCN Centre for Mediterranean Cooperation in collaboration with the Regional Activity Centre for Specially Protected Areas (RAC/SPA), within the MedPAN North project funded by the European Regional Development Fund, the Spanish Agency for International Cooperation and Development (AECID) and the RAC/SPA biannual programme funded by the Mediterranean Trust Fund of the Barcelona Convention.
The publication intends to give some guidance to MPA managers on how to measure the impact of climate change on the marine biodiversity of protected areas and how to improve the planning for the mitigation of this threat. Managers may choose, within several monitoring plans and indicators, the ones that best fit their particular circumstances and management objectives.
Several impacts of climate change in the Mediterranean are identified in this guide, such as sea warming, sea-level rise and salinity and sea circulation changes. Existing information shows that shallow sea waters have already warmed by almost 1 °C since the 1980s. The observed or potential consequences of these shifts on the marine communities are described in the publication.
According to the report, research shows that native species distribution is already evolving, as some warm-water species have started to colonize areas where they were previously absent. For example, the ornate wrasse Thalassoma pavo increased its population density tenfold within less than 5 yeas of its arrival in the Scandola Marine Reserve (NW Corsica, France).
Sea warming also causes mass mortalities of macrobenthic communities (corals, gorgonians, sponges), in particular in the North-Western Mediterranean, and favors the bloom of opportunistic organisms like the P. noctiluca jellyfish.
As for the increased sea acidification, it can potentially affect the growth, reproduction and activity rates of different species.
“MPAs play a key role in the analysis of the biological consequences of climate change. As they are better shielded from anthropogenic impacts than other areas, they can serve as “sentinel sites” where the effects of climate change can be studied and management strategies can be developped to adapt to such negative effects, and wherever possible counter them”, explains Maria del Mar Otero, IUCN Centre for Mediterranean Cooperation Marine Programme Officer and coordinator of the publication.
Based on the experience of a selection of MPAs, the guide presents several case studies, each highlighting a stake of the impact of climate change on marine biodiversity : vulnerability risk of sea turtle nesting faced towards sea-level rise, the resilience of the Mediterranean coral Cladocora caespitosa or species shift distributions observed along the Mediterranean through monitoring. The guide outlines different issues and potential monitoring methods, as well as adaptation strategies to protect the local biodiversity.