Greece’s EU‑backed fish farms are marketed as green, but locals say they’re suffocating vital seagrass. Here’s what real sustainable aquaculture must look like.
Most people hear “Mediterranean fish farm” and think low‑carbon protein, turquoise water and a neat win for the green economy. In Evia, Greece, what locals see instead is sludge.
When fishermen there describe former seagrass meadows turned into a “quagmire,” they’re not arguing about aesthetics. They’re describing the slow breakdown of a supposedly sustainable solution: intensive sea bream and sea bass aquaculture, heavily backed by European Union funds and Green Deal rhetoric.
This matters because fish farming is positioned as a pillar of Europe’s green transition and food security strategy for the 2030s. If the flagship projects aren’t actually protecting marine ecosystems or coastal communities, then the model needs fixing fast—not scaling 24x.
Below, I’ll unpack what’s happening in Greece, why it exposes a bigger flaw in how we badge things as “green,” and what a genuinely sustainable aquaculture strategy should look like for policymakers, investors and coastal communities.
What’s Really Happening in Greece’s EU‑Backed Fish Farms?
Greek aquaculture is large, profitable on paper, and politically favored—but its footprint is landing on fragile marine ecosystems and local livelihoods.
Greece produces over 140,000 tons of farmed fish a year, worth more than €700 million, and is the EU’s top producer of farmed sea bream and sea bass. Around 80% of that is exported, mainly to Italy, Spain and France. To Brussels, that looks like a success story: local production, protein security, rural jobs.
On the water, the picture is different:
- Farms are zoned to expand to 24 times their current acreage.
- Cages often sit near, or directly above, Posidonia oceanica seagrass meadows—legally protected habitat that stores carbon and supports fisheries.
- Several of these zones overlap Natura 2000 marine protected areas that EU law is supposed to safeguard.
Residents on Evia and in western Greece are now taking this to court and to the European Commission, arguing that the “green” label doesn’t survive contact with the seabed.
The core issue: you can’t call something sustainable if it depends on ignoring your own environmental laws.
Why Posidonia Seagrass Is the Quiet Victim
If you care about climate, you should care about seagrass as much as forests. Posidonia is one of the Mediterranean’s most powerful climate allies, and it’s exactly what poorly sited fish farms are damaging.
What Posidonia actually does
Posidonia oceanica forms dense, bright‑green underwater meadows in shallow waters down to about 40 meters. These meadows:
- Act as nurseries for countless fish and invertebrates.
- Stabilize sediment and reduce coastal erosion.
- Store large amounts of blue carbon in both their leaves and the seabed below.
Destroying Posidonia doesn’t just remove habitat; it also releases carbon that’s been locked away for centuries. From a climate perspective, that’s the opposite of “green technology.”
How fish farms damage seagrass
Intensive marine fish farms concentrate thousands of fish in floating cages. That concentration comes with two big by‑products:
- Uneaten feed and feces that fall through the cages and smother the seabed.
- Shading from cages and surface infrastructure that blocks sunlight.
Greek marine biologist Ioannis Karakassis has shown that Posidonia is affected up to 400 meters from cage edges. Research dives by independent consultants have documented areas under and around cages where seagrass is dead or clearly degraded—sometimes in places where official environmental impact studies claimed no Posidonia was present at all.
The legal context is blunt: both EU and Greek law prohibit siting fish farms on Posidonia meadows. If those meadows are there and being destroyed, it’s not a grey area. It’s non‑compliance.
The Clash Between Green Deal Rhetoric and Local Reality
Here’s the thing about Europe’s “green” aquaculture push: the climate logic is mostly sound, but the governance is weak.
Why the EU loves aquaculture
From Brussels’ perspective, aquaculture ticks key boxes:
- Lower average greenhouse gas emissions per gram of protein than beef or pork.
- No need for freshwater irrigation.
- Potential for rural jobs and reduced dependence on fish imports.
The EU has backed those goals with money:
- ~€1.2 billion for aquaculture from 2014–2020.
- Another €1 billion for 2021–2027.
- Greece alone has received more than €700 million in aquaculture‑related support over the past decade from different EU funds.
On top of that, there’s marketing. In March this year, the EU launched a campaign to boost public acceptance of aquaculture, featuring video tours of “sustainable” farms—including one in Marmari, Evia, filmed in what locals argue are already degraded waters.
What local communities experience instead
Talk to residents in Evia, Xiromero or other coastal municipalities and a different narrative comes through:
- Environmental decline: murky water, loss of visible marine life like starfish and crabs, decaying seagrass.
- Weak enforcement: environmental studies that miss obvious Posidonia, monitoring done “from afar,” and sites green‑lit inside or right next to protected areas.
- Thin local benefits: low wages at farms, minimal spillover investment, and tourism or small‑scale fishing at risk.
A recent University of Piraeus study backs this up. Despite heavy subsidies, Greek aquaculture contributed only 0.35% to the national economy in 2023, with stagnant employment and rising environmental conflict. That’s a poor trade‑off: real ecological costs for marginal macroeconomic gains.
So you get banners on beaches that read: “No more fish farms, we want clean seas.” Not because people are anti‑technology, but because they’re tired of being asked to sacrifice their coastline for an industry that ships most of its benefits abroad.
What Sustainable Aquaculture Should Actually Look Like
The reality? Greener fish farming is absolutely possible—but not under a “build fast, monitor later” model. If the EU wants aquaculture to be part of a credible Green Deal, a few conditions are non‑negotiable.
1. No farms on seagrass. Full stop.
This is the minimum bar, and it’s already law on paper. To make it real:
- Require high‑resolution seafloor mapping (diver surveys, sonar, drone imaging) before permits are granted.
- Reject or relocate any site overlapping Posidonia or other key habitats.
- Make baseline habitat maps publicly accessible so communities and researchers can verify them.
2. Stop using protected areas as zoning targets
Natura 2000 areas exist to protect specific species and habitats. Using them as convenient aquaculture zones flips that logic.
Where farms are already inside Natura 2000:
- Conduct independent impact assessments focused on the actual conservation objectives of each site.
- If damage is confirmed and can’t be mitigated, commit to relocation with a clear timeline.
- Tie continued EU funding to proof of compliance, not just paperwork.
3. Make waste and water quality measurable, not theoretical
If tens of thousands of fish are living in each cage, waste will be significant. The question is whether the system is designed and managed to absorb it.
Regulators and farm operators should be tracking, publicly, at minimum:
- Sediment organic content under and around cages.
- Dissolved oxygen levels and seasonal trends.
- Benthic biodiversity (what’s living on and in the seabed).
If thresholds are exceeded, there should be automatic consequences: lower stocking densities, fallowing of sites, or loss of license. Without hard triggers, “monitoring” just becomes another report on a shelf.
4. Align subsidies with performance, not promises
Right now, a farm can access millions in EU support while operating in a way that undermines EU habitat law. That’s absurd.
A better design is straightforward:
- Attach environmental performance conditions to all aquaculture subsidies.
- Make renewal of funding contingent on independent audits and verifiable data.
- Prioritize investment in low‑impact systems: offshore farms in deeper, more dynamic waters; integrated multi‑trophic aquaculture where shellfish and seaweed absorb some of the waste; and innovations in low‑impact feed.
5. Put coastal communities in the decision‑making loop
Social acceptance isn’t a PR problem; it’s a governance problem. Projects imposed on communities rarely end well, especially when they’re visible from someone’s front door.
A more honest process would include:
- Binding public consultation before zoning and permit approvals.
- Local representation in marine spatial planning boards.
- Transparent breakdowns of who gains what: jobs, tax revenue, tourism impacts, and environmental risk.
If a village is giving up tourism value or traditional fisheries, they should at least be gaining secure, well‑paid jobs and visible investment in local infrastructure.
What This Means for Policymakers, Investors and Coastal Leaders
Most countries standing up “green” growth strategies are going to confront this exact tension: low‑carbon doesn’t automatically mean low‑impact.
For policymakers and regulators, Greece is an early warning. If EU law on protected habitats can be bent this far in a member state that’s central to aquaculture, the credibility of the whole blue economy agenda is at risk. Tightening environmental enforcement isn’t anti‑development; it’s how you protect the legitimacy of climate solutions.
For investors and project developers, the message is blunt. Projects that depend on ignoring seagrass, Natura 2000 boundaries or community concerns are reputationally toxic and increasingly exposed to legal challenge. Capital should be flowing into operations that can show their footprint transparently and withstand scrutiny.
For mayors, local councils and community groups, the Greek cases offer a playbook:
- Document local seabed conditions with divers, drones and photos.
- Compare that reality to what environmental impact assessments claim.
- Use existing EU law on habitats, Natura 2000 and funding compliance as leverage.
You don’t have to be anti‑aquaculture to demand that it respects the water it depends on.
As we head into 2026 and debates over the EU’s 2028–2034 budget intensify, there’s a narrow window to fix this. Brussels plans at least €2 billion more for fisheries and aquaculture. That money will either entrench a flawed model—or help create coastal food systems that are genuinely compatible with climate goals and thriving seas.
The choice is stark: fish farms that suffocate the “green” of Posidonia, or fish farms that coexist with it. If Europe wants people to trust its green technology story, it needs to pick the second path and prove it, seagrass by seagrass meadow.