In the Mediterranean Sea, climate change is exerting additional pressure on marine resources already depleted by overfishing. Warming waters — along with reduced dissolved oxygen levels and acidification (also known as low pH) — are exacerbating the stress on species already grappling with overexploitation, pollution and other disturbances caused by humans. All this also has cascading effects on those people whose livelihood depends on fisheries.

Last December, Nathalie Hilmi, environmental economist from the Monaco Scientific Center, talked about the challenges of adapting Mediterranean fisheries to this changing scenario at a conference held in Barcelona focusing on “A Changing Mediterranean Climate: When Adaptation Becomes a Priority.” Drawing on her presentation, we spoke with her about the Mediterranean fisheries and how they can adapt to the effects of climate change and be managed to allow marine life to replenish and even, to some extent, contribute to mitigating the climate crisis.

For a long time, overfishing has been the most significant threat linked to human activities across the Mediterranean. Although the percentage of overexploited fish stocks decreased to 58 percent in 2021​​, most Mediterranean fish stocks are still being fished beyond their biologically sustainable thresholds. In addition, over the past few decades, fish populations have also been subject to myriad pressures due to human activities: pollution, reduced dissolved oxygen levels, habitat degradation and warming caused by emissions from burning fossil fuels. Some fish species are relocating in search of their ideal temperature range. Others are expected to shrink their size to adapt to the changing environment or decline in numbers. According to this study in Ecological Economics, important commercial species, such as the European sprat and the common sole, might be the species most affected by a warming Mediterranean. At the same time, species that better tolerate higher temperatures have started to appear in areas where they were not previously found. With Nathalie Hilmi we’ve tried to understand what’s at stake for Mediterranean fisheries.

NATHALIE HILMI: As a macroeconomics and international finance expert, Hilmi has been leading the Monaco Scientific Center’s environmental economics department since 2010. Her work, at the intersection of environmental sciences and economics, has mostly focused on the socioeconomic impacts and costs of action versus inaction with regard to carbon emissions. Hilmi has been a lead author for the Intergovernmental Panel on Climate Change (IPCC) Special Report on "The Ocean and Cryosphere in a Changing Climate" and the “Impacts, Adaptation and Vulnerability” part of the latest IPCC report assessing the state of climate change science.

This interview has been edited for length and clarity. Most of the interview was conducted via Google Meet. The last four questions were answered over email.

How does climate change affect the fisheries in the Mediterranean and what can be done to adapt?

We have three most important threats: warming waters, deoxygenation and acidification. Warming is particularly important, as fish species [that are typically found in southern waters] are moving northward in the Mediterranean. Some species are disappearing because of warming. So, maybe, one way to adapt is to change the species that we fish and eat. And this is related to the lionfish [and other exotic species that are expanding their presence in the Mediterranean].

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