Aquaculture is the world’s fastest-growing food production system. The sector now supplies half of all seafood consumed, providing livelihoods for millions of people, and is expected to double in size by 2050 to match increasing global demand.
Environmentally speaking, however, aquaculture often gets a bad rap – and often with good reason. From Norwegian salmon farms that source feed from indiscriminate trawlers that destroy vulnerable ecosystems and fishers’ livelihoods to Southeast Asian shrimp pond operations that overuse antibiotics and displace carbon-rich mangrove forests, the sector has a checkered history.
But aquaculture also offers opportunities to cultivate nutritious foods at a very low environmental cost. It presents some novel ways to restore the ocean and its ecosystems, too.
“As aquaculture expands in freshwaters and the ocean, there’s an opportunity to avoid the mistakes people have made farming on land that have led to habitat and biodiversity loss,” said the co-authors of a recent study that outlines 12 ways aquaculture can benefit ecosystems, in a press release.
That means being selective about what kinds of seafood we choose.
“There are some species in particular that should be prioritized for helping to meet food security demands, which can also provide ecological benefits,” said Kathy Overton, a PhD researcher at the University of Melbourne’s Sustainable Aquaculture Laboratory and the article’s lead author.
These are typically ‘low-trophic’ level species: those near the bottom of the food chain, rather than the top, that feed largely on plankton, such as shellfish and seaweeds.
There’s now a large body of evidence showing that this kind of marine farming can help restore ecosystems while also nourishing communities – provided it’s cultivating the right species, using the right practices and in the right places.
An inspiring example is New Zealand-based Whakatōhea Mussels, owned and run by the Whakatōhea iwi (tribe) in the eastern Bay of Plenty region. The group operates the country’s first-ever open-ocean green-lipped mussel (Perna canaliculus) farm, which stretches over 3,800 hectares of ocean, 8.5 kilometers offshore from the town of Ōpōtiki, where its processing factory is based.
Mussels are ideal candidates for sustainable aquaculture in many locations for several reasons: they don’t need feeding or fertilizer, they filter the water in which they live, and the floating farms tend to be quite simple, light on resources and easy to move.
Ōpōtiki is one of the country’s most economically-deprived areas and has high levels of intergenerational unemployment, so the primary motivation for creating the farm and factory was to provide jobs. But there are also strong environmental and cultural threads to the work, such as restoring depleted wild mussel beds and using mātauranga (traditional Māori knowledge) to weave plastic-free ropes out of native plants.
What’s more, as Overton and her co-authors make clear, aquaculture is not just about growing food: it can also be used for species recovery.
“There are a lot of species right now that are being recovered in freshwater, coastal and marine ecosystems, where we’re using aquaculture and associated techniques to produce individuals to then reintroduce into the wild,” she said.
For instance, in Australia, the Macquarie perch (Macquaria australasica) has been fished to very low levels, but scientists are now using aquaculture to build up population numbers in captivity and then ‘restock’ the rivers – with strict regulations surrounding them so they can’t then be fished back out.
As a result, “we’re seeing that the wild populations are slowly recovering,” said Overton, “and that’s really exciting.”
Aquaculture can also help restore degraded ecosystems. “There are a lot of incidences where we’re culturing different kinds of species that are ‘ecosystem engineers’, which form or create ecosystems,” said Overton. A prominent example is coral reef restoration, whereby fragments from degraded reefs are extracted and grown in nurseries, and then ‘grafted’ back onto the reefs.
Mussel and oyster reefs can also be restored in similar ways. “Aquaculture is a key part of our process to rebuild lost shellfish reefs through creating healthy oyster and mussel juveniles to kick-start the reef restoration process,” said Simon Branigan, Marine Restoration Lead at The Nature Conservancy (TNC) Australia.
While these kinds of benefits are absolutely possible, projects and industries must be scrutinized carefully to ascertain whether they’re genuinely doing more good than harm.
To that end, TNC recently released a report, titled Global Principles of Restorative Aquaculture, which offers a definition of the approach, six guiding principles, and implementation roadmaps “to help industries, governments and communities develop aquaculture in a way that actually benefits nature.” The principles are as follows:
Policymakers and industry heads would do well to create regulations along these lines that ensure aquaculture projects purporting to be sustainable really do pass muster, said Overton and her co-authors.
“By requiring a high standard of evidence to label something ‘ecologically beneficial’, this reduces potential for ‘greenwashing’, where aquaculture industries might claim to be providing ecological benefits that aren’t really there,” said Tim Dempster, a professor of marine biology and aquaculture at Deakin University.
This means looking holistically at the footprint and benefits of a particular farm or operation. “We want to ensure that aquaculture practitioners monitor their ecological impact before claiming their farm creates ecological benefits,” said Dempster.
“Just because a particular aquaculture activity does one positive thing doesn’t mean that it will deliver an overall benefit to the environment. It’s important to weigh up overall impacts when deciding if something is ecologically beneficial or not.”
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