Climate change is now putting additional pressure on biodiversity. According to the fourth International Panel on Climate Change (IPCC) report, Mediterranean ecosystems, which carry significant and vulnerable biodiversity, would be among the most threatened by the announced climate change. The Mediterranean Sea has a specific climate with four different seasons and high interannual variability.

Climate change has several consequences: sea level rise, temperature rise, change in the physicochemical characteristics of the water, change in the species.

The most critical impact of climate change is the sea-level rise, due to the thermal expansion of water as a result of rising temperatures, and the influx of water from glaciers. Ecosystems must adapt if they can. It is crucial to study these adaptations. However, this rise remains challenging to predict at the regional level and in particular in the Mediterranean basin.

The temperature of the water also increases, but this increase is not observed uniformly on the whole globe. This increase reinforces the stratification of surface waters, leading to a reduction in nutrient input, leading to a decrease in primary production. All this favors the expansion of oceanic deserts and invasive species (including pathogens) but also impacts Mediterranean intertidal areas by altering the physiology of several key species. As these have a significant ecological role, there could be cascading effects on the entire environment.

Climate change is, therefore, a significant contributor to biodiversity loss. The most affected species will be those already vulnerable or those with high demands (restricted climate distribution, specific needs).

Based on a moderate climate change scenario, the assumption of extinction of 15 to 37% of the species occupying the northwestern Mediterranean by 2050 is foreseeable. For the moment, it does not seem possible to predict the extent of the proliferation of thermophilic species. The Mediterranean is currently going through a process of southernization.