The science of sustainable seafood, explained

In 2050, fish will play an important role in sustainable diets

The environmental cost of food

Growing crops and raising livestock requires an enormous amount of space and water: agriculture uses roughly half of Earth’s vegetated land and accounts for over 90% of freshwater use. Agriculture is the largest driver of biodiversity loss, comparable to the last major asteroid. Further, about a third of all greenhouse gas emissions are the result of food production. 

Yet, global population is growing, there will be more and more mouths to feed—how can we feed 2-3 billion more people while protecting biodiversity and limiting global warming to acceptable levels by 2050? A new report by the World Resources Institute (WRI) offers some answers. It summarized and explained the three main challenges…

  • A 56 percent food gap between crop calories produced in 2010 and those needed in 2050 under “business as usual” growth;
  • A 593 million-hectare land gap (an area nearly twice the size of India) between global agricultural land area in 2010 and expected agricultural expansion by 2050; and
  • An 11-gigaton GHG mitigation gap between expected agricultural emissions in 2050 and the target level needed to hold global warming below 2oC (3.6°F), the level necessary for preventing the worst climate impacts.

…then outlined five major policy goals that would preserve land and reduce agricultural greenhouse gas emissions to acceptable levels while also producing enough calories to feed everyone:

  1. Reduce growth in demand for food and other agricultural products
  2. Increase food production without expanding agricultural land
  3. Protect and restore natural ecosystems
  4. Increase fish supply
  5. Reduce GHG emissions from agricultural production

Seafood plays a part in each of the 5 policy goals and will have a large role in a sustainable future.

Protein, food, and shifting diets

Protein consumption is directly tied to wealth. As a country becomes wealthier, its per-capita protein consumption increases, particularly animal protein. Demand for animal protein will rise significantly as more of the world increases wealth over the coming decades.

Data from OECD-FAO Agricultural Outlook 2015

Unfortunately, animal protein is the most resource-intensive food to produce, costing the most in land, freshwater, and emissions.

Shifting diets away from beef and towards less-impactful proteins is the most important policy goal for dietary sustainability in 2050. Increasing the amount of available seafood will help with that goal as, on the whole, farmed seafood is less resource-intensive than other forms of livestock and wild-caught seafood is the least impactful animal-protein available. Some species have lower impact than others, but generally, eating seafood in place of other kinds of animal protein is good for the planet. There are even some seafood products that are less impactful than most plant-based foods. For example, farmed bivalves like oysters and mussels are potentially the best thing to eat for the planet regardless of food-type: they filter water to improve habitat, take carbon out of the environment mitigating emissions, and are often grown just offshore using no freshwater and little to no land.

Shifting diets to less land & freshwater intensive foods is important to preserve habitat and biodiversity; fish can also help shift to lower-emissions diets. For example, a 2014 study in Climatic Change (open access) examined the daily emissions of different kinds of diets. Researchers categorized people into groups: high, medium, and low meat-eaters; fish-eaters; vegetarians; and vegans. The results are mostly what would be expected: eating more meat produces more emissions, unless the only meat consumed is fish. Fish-eaters (who consumed no other meat) have nearly the same emissions profile of strict vegetarians, differing by about 1%. Vegans are the least impactful eaters.

From Scarborough et al. 2014

If you’d like to read more in-depth discussion of different kinds of food and their associated environmental impacts, two important papers came out earlier this year. I wrote about them both in a general way in this post, but also covered them separately: Hilborn et al. 2018 compared all animal proteins including wild-caught and farmed seafood, while Poore and Nemecek 2018 compared all terrestrially produced food. 

You can also read more about seafood’s role in global food systems and a more generalized look at the environmental cost of food in our Sustainable Seafood 101 series.

Increasing fish supply

WRI’s report demonstrates why fish are important to a sustainable dietary future, but how are we going to significantly increase the amount available to eat?

  1. Increase aquaculture production
  2. Improve management of wild-caught fish; fishery potential

Much of the increase in fish supply will be provided by growing aquaculture industry. Already, about half of the world’s seafood is farmed, with that proportion set to grow dramatically over the next few decades.

The graphic above shows WRI’s “business as usual” scenario where wild-caught fish harvests continue to slightly decline, leading to a 10 percent reduction in wild catches between 2010 and 2050, and putting the burden entirely on aquaculture to expand world fish supply. However, improving fishery management would also lead to an increase in sustainable, wild-caught fish. Currently, about 80 million tons of wild fish are harvested each year. Estimates vary for how much fish could eventually be sustainably harvested, but they range from about 95-120 million tons. A recent study estimated that if better management practices were implemented around the world, by 2030 over 90% of existing fisheries could be sustainable. By 2050, the amount of fish in the ocean would double, which would produce a global maximum sustainable yield of around 95 million tons.

Further, this only accounts for existing fisheries. There are plenty of potential commercial fisheries around the world that do not exist yet, for varying reasons. Some potential fisheries do not have a market, meaning consumers don’t like eating them for reasons ranging from taste to perception. These potential fisheries are reliant on chefs, restaurants, and experimental home cooks to develop new recipes or marketing firms to change perceptions. Slimefish were once looked down upon as trash-fish, but are now a delicacy around the world rebranded as orange roughy. Other fisheries remain untouched due to capacity issues. Some fisheries are either too costly or too difficult to reach for the managing country. These fisheries will develop as technology develops and/or harvesting becomes cost-efficient.

In sum:

WRI’s most recent report highlights the importance of seafood for a sustainable food future. Shifting diets away from high-impact protein like beef towards low-impact protein like fish will be an important part of preserving biodiversity, forests (land), freshwater, and reducing dietary carbon impacts. Increasing seafood supply will be crucial as global population continues to rise and incomes grow. Aquaculture will contribute much of the increase, but fishery management improvements around the world could also increase the amount of sustainable seafood available for consumption.

The report can be found in full, here, but the authors also released a blog explaining the report in several charts that I recommend checking out here.

Picture of Max Mossler

Max Mossler

Max is the managing editor at Sustainable Fisheries UW.

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