We can farm more seafood while minimizing its impact on biodiversity, U-M research shows

(Press-News.org) Humanity can farm more food from the seas to help feed the planet while shrinking mariculture's negative impacts on biodiversity, according to new research led by the University of Michigan. 

There is a catch, though: We need to be strategic about it.

"We can achieve this sustainable mariculture development," said Deqiang Ma, who led the study as a postdoctoral researcher at the U-M School for Environment and Sustainability. "With strategic planning, we can achieve the goal of conserving marine species while meeting the global demand for the expansion of mariculture."

Mariculture is the branch of aquaculture that farms saltwater seafood. In 2020, it accounted for about a fifth of the food farmed from fisheries, which is an important source of protein for billions of people worldwide.

Demand for seafood is going up and mariculture production is growing rapidly to help meet that, Ma said. To predict the impact of that growth, Ma and an international team of researchers developed a model to assess mariculture's effects on the populations of more than 20,000 species of marine fauna.

The model allowed the team to establish a baseline for mariculture's current impacts and forecast how those would change by 2050 under a range of scenarios, depending on, for instance, what was farmed where. The model also looked at two different climate scenarios, known as RCP 4.5 and 8.5, assuming different levels of warming and greenhouse gas emissions.

The best-case scenario—building the most farm capacity in the areas with the lowest environmental impact—produced exciting numbers for both bivalve shellfish and "true" fish, or finfish.

"Bivalve production could increase by 2.36-fold and finfish could increase by 1.82-fold compared to current production—projections of what is needed to meet global demand—but the global mariculture impacts would decrease by up to 30.5% under the best-case scenario," Ma said.

On the flipside, the worst-case scenario was also striking. If new farms are built in the areas that would have the most detrimental impact on biodiversity, it would be over four times worse than building them at random sites.

This underscores the importance of strategic planning, said U-M senior study author Neil Carter, and of working with experts from a variety of fields who can assess a wide range of considerations.

"It is critically important to leverage the growing insights across disciplines, whether it's climate change science or economics or marine production," said Carter, associate professor of environment and sustainability. "All these different facets had to come together from other sources in order to make these forecasts."

The team included researchers from the University of Washington, the University of Freiburg in Germany, Hokkaido University in Japan and the University of California, Santa Barbara.

The scope of the analysis and the collaboration required to perform it can create challenges for projects like this, said study co-author Benjamin Halpern, a professor at UCSB.

"But I've done this kind of work a lot in my career, and the payoffs can be enormous," said Halpern, who is also the director of the National Center for Ecological Analysis and Synthesis. "The cross-disciplinary nature of the questions that can be addressed and the ability to look at them for every patch of ocean in the world makes the research much more relevant and impactful to society and the scientific community."

Ma and Carter stressed that the paper is a first step toward building mariculture's most sustainable future. Scientifically speaking, the model can be refined by including more and newer data moving forward.

The research also showed there isn't a one-size-fits-all solution to grow mariculture sustainably. From a research standpoint, the opportunities for farm development are different in the South Pacific than they are along the coast of France.

And the decisions made to work toward the world's best-case scenario can still have drawbacks. Developing mariculture had a negative impact on important and iconic marine mammals—including whales, seals and sea lions—in all the scenarios analyzed by the team.

But understanding these limitations and trade-offs helps researchers and policymakers better anticipate the impacts of important decisions before they are made.

"With these insights, we can see that it's not a foregone conclusion that the expansion of an industry is always going to have a proportionally negative impact on the environment," Carter said. "So the next part of this is getting policymakers and communities to interact with each other to figure out how we can actually implement some of these ideas to reduce those impacts and to prioritize marine biodiversity."

The project was funded by the U-M School for Environment and Sustainability and the U-M Institute for Global Change Biology.

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