Aquaculture: The Lesser Of Two Evils?

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Fish and other marine animals often exist in a hazy limbo on the periphery of humans’ circle of moral consideration. We meet pescatarians who eschew most animal flesh but make an exception for sea creatures. Many people who eat meat but are squeamish about the process by which it is procured are comfortable getting personally involved in the slaughter when they fish recreationally. Even among the animal advocacy community, it can be difficult to know how highly to prioritize the protection of these animals with nervous systems so different from our own. This study, which focuses not on aquaculture’s impact on fish but rather on its impact on the environment, gives animal advocates another angle from which to evaluate the merits and drawbacks of fish farming.

A 2020 report from Nature and the Food and Agriculture Organization of the United Nations (FAO) took on the ambitious task of quantifying the greenhouse gas (GHG) emissions of global aquaculture from cradle to farm gate. This required not just measuring the impact of direct fish farm operations — the electricity used for pumping and lighting and the fuel for farm vehicles — but also the land use change, fertilization, cultivation, transportation, and blending of feed and the GHG emissions from water nitrification. They calculated these emissions by species type and by region, yielding an impressively granular view of GHG emissions at every stage. The investigators used the most up-to-date data available from the FAO, journal articles, and experts in the field. They collected data for the key species groups in the key producing regions until they could account for 93% of global production, and then extrapolated from these data to estimate the remaining 7%. Some findings may be slightly off due to ever-changing feeding practices and some of the data sets being a few years out of date, but the overall picture should be relatively accurate.

The study was undertaken with the assumption that aquaculture is important to nutrition and employment worldwide, and the expectation that the industry will continue to expand. Animal advocates tend to share a concern for the environment and support efforts to expand industry sustainably, where expansion is necessary. A healthier planet certainly serves the interests of the animals that live here. However, given that aquaculture is an industry that revolves around the exploitation and slaughter of animals, advocates generally do not welcome its expansion. Still, an understanding of the merits of aquaculture relative to land animal agriculture and plant agriculture can inform our advocacy direction and priorities.

The study found that feed production accounts for 57% of aquaculture GHG emissions. Finfish, shrimp, and prawns generate more GHGs kilo for kilo than bivalves. Finfish are high emitters because many finfish are fed other fish and because they convert feed to muscle inefficiently. Shrimp and prawns are high emitters because of the energy required for water aeration and pumping. Bivalves have a lower emission-to-end product ratio because they feed on nutrients already present in their environment. In general, fish convert feed to muscle more efficiently than land animals because their lifestyle requires less energy expenditure and their fertility is higher. So while aquaculture has an emission intensity (EI — a measure of GHG emissions per kilo of carcass weight) under 10 kgCO2e/kgCW, cows have an EI closer to 50, sheep and goats have an EI close to 40, and pigs and chickens have an EI comparable to that of aquaculture. 

These data show that a shift from animal agriculture to aquaculture could have environmental benefits. What is less clear is whether such a shift would be an improvement or a step backward for animal welfare. In terms of its environmental impact, its usefulness as an intermediate step toward animal liberation, and its potential animal welfare gains, aquaculture is a mixed bag.

Environmental Impact

According to these estimates, aquaculture accounts for about .49% of human-caused GHG emissions, which is roughly equivalent to the GHG emissions of sheep farming. Sea creatures are far more environmentally friendly than all land animals used for food except chickens and pigs in terms of EI. This means, with a few subgroup exceptions, it’s much better for the environment to produce a kilo of fish or clam meat than a kilo of beef. As fish farming is a relatively young industry compared with the farming of land animals, the authors believe there is great potential for future innovation which could further decrease the environmental impact of aquaculture.

Of course, animals are not the only source of protein available to us. While it is more environmentally responsible to rear finfish and bivalves than it is to rear cows and sheep, it is more responsible still to grow grains, legumes, and nuts. It’s difficult to argue for the environmental improvement represented by a shift from cows to fish when an even more environmentally sound option already exists.

An Intermediate Step

As evidenced by the existence of pescatarians, there are people who at present are unwilling or unable to give up meat altogether, yet are taking steps to “limit” their consumption of animals in some way. This can seem an ethically inconsistent position, but it may be useful as a step on the way to a diet free of meat. A person who initially feels overwhelmed at the prospect of becoming vegan or vegetarian may first become pescatarian, and find that she is still able to have a fulfilling relationship with food. This may then give her the confidence to make more changes and eventually embrace a diet free from animal exploitation.

Cutting land animals out of one’s diet could be a stepping stone to a more ethical diet. However, the existence of millions of veg*ns and the broad and ever-expanding array of veg*n products available call into question whether such an intermediate step is necessary. Whether motivated by environmental concerns or animal welfare concerns, it is better and increasingly feasible to give up fish along with land animals.

Animal Welfare

This is perhaps the murkiest water to navigate. On the one hand, a shift from animal agriculture to animal aquaculture could mean a shift from killing “higher-order” beings to killing “lower-order” beings. However, it’s becoming well established that finfish experience pain and suffering, though it’s less certain with neurologically simpler animals like bivalves. An absence of proof is not proof of absence, of course, but one could argue that it is preferable to kill an animal whose sentience is unproven than one whose sentience is clearly evident.

On the other hand, if consumers of beef and pork switch to clams and oysters, far more lives will be taken. Many small sea creatures would have to be slaughtered to produce as much meat as a single cow. From an animal welfare standpoint, a shift in consumption is at best a marginal improvement from killing more sentient creatures to killing less sentient creatures. At worst it is a huge step in the wrong direction, from killing few creatures to killing many creatures. And overall, the whole undertaking is unnecessary. No one has to die. In a world where there are nuts and beans and peas and grain, it’s hard for animal advocates to find common cause with those who would expand aquaculture. 

Conclusion

This study provides a tidy summary of aquaculture’s environmental impact, and we recommend you take a look at their tables and charts for more detail than we could provide here. As animal advocates, though, the best we can say for aquaculture is that a shift from other meat to fish consumption could be a stop-gap solution on the way to the total cessation of animal exploitation. Animal advocates cannot wholeheartedly support a move in the direction of greater environmental sustainability but more death, especially when a solution with better environmental outcomes and no cruelty is staring us in the face. If you must eat sea creatures, perhaps you should eat bivalves because they have the smallest environmental impact and the lowest probability of sentience. However, if like most people, there is no circumstance compelling you to eat any animal at all, stick with plants. 

Our Faunalytics Explains video series includes this summary in video form. Check it out and share widely!