Industrial fish farming is often promoted as a “climate-smart” way to produce protein. Compared to beef or wild-caught fish, aquaculture is framed as a lower-impact option that can help feed a growing global population without worsening climate change. The data tells a different story.
On average, farmed fish generate about 13.6 kg of CO₂-equivalent emissions per kilogram of food. That’s higher than poultry, and dramatically higher than plant proteins like tofu, legumes, and nuts. Fish farming also requires far more resources, including roughly ten times more freshwater than beans or soy. These are not the numbers of a low-impact food system.
The climate impact of fish farming begins with feed. Aquaculture depends heavily on wild-caught forage fish for feed, which means that, rather than reducing pressure on oceans, it intensifies it. Roughly 25% of the global ocean catch is diverted into fish meal and fish oil (FMFO), primarily from small but ecologically critical species like sardines and anchoveta, with most of this feed used for farmed fish. In regions such as West Africa, rapid industrial expansion has pushed local fisheries into “overexploited” status. Similarly, Peru’s anchoveta fishery, the world’s largest FMFO source, has faced repeated season closures between 2022 and 2025 due to low biomass and high juvenile catch rates, signaling stock depletion. This overexploitation disrupts marine ecosystems, as forage fish underpin food webs; their decline has been linked to falling seabird populations in West Africa and South America and contributes to the endangered status of species like African penguins and Cape cormorants, illustrating the reverberations of this ecological destruction.
As concerns about “overfishing” have grown, the industry has begun to shift toward plant-based feed ingredients such as soy and rapeseed. This change is often presented as a sustainability improvement, but it comes with its own environmental harms. Growing these crops requires dedicating large amounts of fertilizer, energy, and land not to feeding human beings, but to feeding fish over the course of their lifetime. The resulting inefficiencies multiply the environmental costs of plant agriculture far beyond those incurred by humans eating plants directly.
Tilapia and catfish are often described as more environmentally efficient because they rely more heavily on plant-based feeds. Yet life-cycle analyses show that emissions from tilapia and catfish aquaculture can still rival or exceed those of other animal proteins. The greenhouse gas emissions from shrimp farming exceed even those of salmon and poultry.
Beyond feed, certain forms of farming the production process itself is highly energy-intensive. Land-based systems known as indoor recirculating aquaculture systems are key offenders. Promoted as more environmentally sound alternatives to open net pens, these facilities filter and reuse water in enclosed tanks, and require an ongoing energy expenditure to pump water, maintain oxygen levels, and regulate temperature. As a result, their carbon burden can be even higher than that of conventional systems.
The climate toll of aquaculture extends beyond its direct emissions. Aquaculture also reduces the planet’s natural ability to absorb carbon.
Oceans, forests, and wetlands play a critical role in regulating the climate by acting as carbon sinks. These ecosystems absorb and store more carbon than they release, helping to buffer the effects of human-caused emissions. Together, they remove more than half of the carbon dioxide released into the atmosphere each year.
Fish farming disrupts these systems in multiple ways. In the ocean, small fish such as anchovies and sardines play a key role in storing carbon. These fish consume plankton near the surface and release waste that sinks to the deep ocean, carrying carbon with it. This process helps lock carbon away for long periods. However, these same species are extracted from oceans to produce fishmeal and fish oil for aquaculture feed, interfering with this natural carbon sequestration. Research has shown that some of the most heavily fished areas overlap with regions that are particularly important for carbon absorption. By extracting biomass from these areas, industrial fishing weakens one of the ocean’s most effective mechanisms for storing carbon.
On land, the expansion of aquaculture feed production contributes to deforestation. As the industry shifts toward plant-based ingredients, demand for crops like soy increases. In regions such as the Amazon, this demand drives the clearing of forests to create agricultural land.
Forests are among the most important carbon sinks on Earth. They store vast amounts of carbon in trees and soil, and continually absorb carbon dioxide from the atmosphere. When forests are cleared, this stored carbon is released, and the land loses its capacity to function as a carbon sink.
Fish farming also damages coastal ecosystems. Shrimp farming, in particular, has been linked to the widespread destruction of mangrove forests. Mangroves are among the most carbon-dense ecosystems on the planet, storing significantly more carbon per hectare than most tropical forests. The ecological benefits they provide include coastline protection, water filtration, and biodiversity support. But since the 1980s, large areas of mangroves have been cleared to make way for shrimp ponds. Once bulldozed for shrimp ponds, that carbon is released into the atmosphere.
The destruction of mangroves and forest ecosystems leads to a catastrophic double impact: the release of previously stored carbon, and the permanent loss of a system that would have kept absorbing more.
Pivoting from aquaculture to wild-caught fish wouldn’t solve the problem. Some wild-caught species, like shrimp, lobster, and flounder, have higher greenhouse emissions than farmed fish and land animals, and even the lower-impact wild fisheries typically exceed the emissions of plant proteins. Industrial fishing also comes with serious ecological costs—destroying habitats, decimating vulnerable populations, and putting further pressure on already stressed oceans.
When the full picture is considered, fish farming, often pitched as a climate solution, actually produces large amounts of greenhouse gases while simultaneously undermining natural systems like oceans, forests, and wetlands that regulate the planet’s climate and sustain its biodiversity.
Aquaculture has successfully greenwashed many consumers by perpetuating the notion that the industry is “climate smart.” It positions itself as a hero in a time of environmental devastation. But aquaculture has taken a real problem—overfishing—and outsourced the damage to forests, mangroves, and oceans most consumers never see.
To learn more about the carbon burden of fish farming, as well as our debunking of five core myths of aquaculture, read our 2026 report.