Drivers of biodiversity loss in the Eastern Mediterranean

The easternmost Mediterranean Sea is experiencing the most dramatic climate -driven biodiversity loss worldwide. The basin is under the additional pressure of tropical species introduced by humans as well as other local stressors, but disentangling their ef fects is often difficult. One frequent problem is the lack of data over sufficiently long periods to assess change and how the ecosystem has evolved. This project will study biodiversity loss in the Eastern Mediterranean by reconstructing data over the last few decades from monitoring projects, museum collections and subfossil samples. We will focus on molluscs and fishes for their importance for the functioning of the ecosystem and the economy of coastal communities. We will then quantify how many Mediterranean species have already been lost due to the profound environmental changes caused by humans, how this loss deteriorates the functioning of the ecosystem, how summer heat peaks affect molluscs and fishes, and how other stressors like tropical species and fishing are contributing to this demise. Eventually, we will model the distribution of species under future climate scenarios to better comprehend the changes ahead of us and plan appropriate restoration and mitigation actions.

Global warming is causing a decline in marine biodiversity around the world. The eastern Mediterranean Sea is especially vulnerable because it is warming faster than any other part of the Mediterranean. At the same time, hundreds of tropical species are entering through the Suez Canal, making local ecosystems increasingly similar to those of tropical seas. Understanding how these changes have unfolded over time is difficult because long-term records are scarce. To address this problem, we compiled information on molluscs-such as snails, clams and other animals that live on the seafloor-from 2005 to the present day. Our results show that many of the major ecological changes had already taken place by 2005. Over the past two decades, most biodiversity loss has been linked to increasingly hot summers. High temperatures can kill many marine organisms before they are old enough to reproduce. In contrast, tropical species arriving through the Suez Canal are able to thrive in the warmer Mediterranean Sea. There is, however, some good news from Cyprus. Along the southern coast of the island, unique ocean conditions bring colder water up from the depths. This natural cooling effect keeps surface waters about 3C cooler than elsewhere in the eastern Mediterranean and helps a wide variety of species survive. As a result, this area has become a priority for conservation efforts.