Protecting coasts around the world is more than ecology, more than economics
The tropical coral reefs of Kiribati in the South Pacific resemble the rocky shores of Rhode Island and the commercial fisheries of western Mexico about as much as ecology resembles economics. Beneath the surface, they share a lot of similarity and overlap.
Unraveling the complex dynamics that sustain or degrade coastal ecosystems is what drives the unique work of Sheila Walsh, a distinguished interdisciplinary postdoctoral research associate with Brown’s Environmental Change Initiative (ECI).
Based in Heather Leslie’s group in the Department of Ecology and Evolutionary Biology, Walsh is trying to help marine managers keep the habitats on an even keel, to preserve the long-term benefits — fisheries, coastline erosion protection, recreation and so forth — that they provide to people.
“What we’re trying to do is use tools from ecology and economics in order to better understand how to design management institutions and to evaluate them,” Walsh said.
She moves between the natural and social sciences as fluidly as tides ebb and flow in a cove. That’s what brought her to the ECI postdoctoral appointment at Brown from the Scripps Institution of Oceanography at the University of California—San Diego a year ago. Her position is explicitly designed to foster a broad intellectual approach and to bring together faculty from different departments at Brown. In addition to Leslie, she is also advised by Sriniketh Nagavarapu, assistant professor of economics.
“My appointment has allowed me to conduct research that is truly interdisciplinary,” Walsh says.”
Making a splash
Walsh’s interdisciplinary work began during her graduate student days, working in the archipelago nation of Kiribati. In a paper published Dec. 15 in the Journal of Marine Biology, she filters out the separate effects that nutrient flows and fishing have on the persistence of harmful algae on the reefs.
In part, the study succeeded because she had the unique opportunity to study the effects of both increased productivity due to ocean currents and a mass migration of population on the island of Kiritimati. But in addition to having such large-scale changes to observe, she also took an interdisciplinary approach. To assess the role of fishing, she not only dove under the water to count fish like an ecologist but also interviewed residents on shore about their fishing behavior like an economist.
Walsh gained some important insights. Herbivorous fish actually accelerate their algae-suppressing eating in areas where algae-promoting nutrients are high. She also found that fishing activity does not promote a larger herbivore population by preferentially removing the biggest, top predator fish that eat them. Instead, when the top predators are in short supply, fishermen move right down the line to the herbivores.
To sustain the reef and the benefits it provides to people, Walsh concluded that reducing fishing, or at least encouraging fishermen to fish species that eat plankton and invertebrates, is the best approach. That way, herbivore populations stay strong and they can continue to unleash their algae-eating prowess to keep the reefs clean.
Bringing it to Brown
At Brown, Leslie, Walsh and other members of the group are testing similar ideas with experiments in the chilly waters of Narragansett Bay. They are carefully manipulating snail populations in areas along a gradient of increasing biological productivity (linked to land-based nutrient pollution) in order to investigate the snails’ role in the rocky shore ecosystem. It may seem arcane, but the stakes are high. Left uncontrolled, microscopic algae on the rocks ultimately create conditions that enable an entirely different habitat — a salt marsh — to take root and grow on protected rocky shores. That would be a fundamental change to the shoreline ecosystems of the bay, Leslie notes.
Walsh’s main project at Brown, with both Leslie and Nagavarapu, is an investigation into how decentralized cooperatives in Mexico can best maintain the health of their fisheries. The key factors in these studies range from studying the fish populations themselves to the cultural and legal context on land.
The study is one that Leslie and Nagavarapu had wanted to do for a while. Leslie credits Walsh for providing an interdisciplinary bridge between them.
“It wasn’t until Sheila arrived at Brown that we really made substantial progress,” Leslie said. “We knew that bringing economics and ecology together was important, but figuring out how to talk to each other about these connections takes time and effort. That didn’t happen until Sheila was here at Brown and pushing us and mediating that conversation.”
Even if ecology and economics seem as far apart as Kiribati and Rhode Island, Walsh is bringing them together.