Impact of human pressures on the Mediterranean Sea’s ecosystem

Around the world marine ecosystems are being stressed by a diversity of anthropogenic activity. Fisheries and aquaculture, pollution (including agricultural run-off), habitat loss and degradation, and species invasion are all putting the ecosystems in seas and oceans under pressure. Human activity is increasing rapidly and the EU-funded MERCES (Marine Ecosystem Restoration in Changing European Seas) project aims to further our understanding of the changing interaction between humans, the environment and marine species.

The Mediterranean Sea is a highly diverse marine ecosystem that hosts 7–10% of the world’s marine biodiversity. Using trend data from 1950 to 2011, the MERCES project has investigated the whole of the Mediterranean Sea and found that anthropogenic activities have played an important role in driving species dynamics. The project recently published a paper in ''Scientific Reports'' in which they present their findings, including their observation of a reduction in abundance of important fish species amounting to a decrease of 34% of both commercial and non-commercial species and 41% of top predators. The team explains that community biomass, trophic levels, catch and diversity indicators all show that the ecosystem has been degraded over time.

MERCES evaluated the temporal responses of species abundance and ecosystem dynamics to changes in primary productivity and fisheries using the Ecopath with Ecosin (EwE) food web model approach. The team focused on eco-system based management (EBM), rather than an evaluation of single resources and threats, using models that allow for the quantitative assessment of the role of different stressors.

The study, ‘Historical changes of the Mediterranean Sea ecosystem: modelling the role and impact of primary productivity and fisheries changes over time’, quantifies temporal dynamics and then calculates a series of ecological indicators to analyse past ecosystem dynamics. Their specific goals were to: investigate the sea’s temporal evolution by developing a hind-cast scenario, to establish differences and similarities in historical ecosystem dynamics through modelling, and to analyse the structural and functional historical changes of the sea’s ecosystems using specific model-based indicators.

They describe their study as a ‘baseline reference’, which can play a role for future research in the face of increasing pressure on the Mediterranean due to the combination of climate change and human activity. Since the intensity of these stressors is increasing throughout most of the Mediterranean basin, temporal analyses are increasingly needed to inform effective current and future marine policies and management actions.

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Project web site