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Why invader species may be taking dinner off your table

The species that live on our coasts provide benefits that most of us are unaware of. Oyster reefs, for example, stabilize the shoreline from erosion and keep the water clean through filtration. Kelp forests provide food for economically important fishes—ones that we also love to eat.

So what happens when the kelp forest is taken over by non-native ascidians, or sea squirts, that hitched a ride from China to Maine on the hull of a shipping vessel? The kelp forest is destroyed, the fisheries are devastated, and our wallets and dinner plates are left empty.

While coastal species are dealing with new challenges like climate-related ocean acidification, they’re also working with the same stressors they’ve faced for centuries, according to David Kimbro, an assistant professor of environmental sciences at Northeastern’s Marine Science Center. Since the days of Columbus, globalization has brought with it foreign invaders that can outcompete native species both on land and in the sea.

“From basic principles, we know that marine and terrestrial systems differ fundamentally,” said Kimbro. But despite those differences, marine management strategies have been based only on findings from terrestrial research.

That’s because similar work on marine systems simply hadn’t been carried out—until now. In a paper recently published in the journal Ecology Letters, Kimbro and his colleagues at the University of California at Davis synthesized nearly two decades’ worth of data from experimental marine ecology. With this so-called “meta-analysis” of other researcher’s work, the team was able to draw new conclusions about the impacts of marine invasive species.

They found that the factors important to a foreign terrestrial species’ success are very different from those for a foreign marine species. For example, native plants tend to be good at outcompeting foreign invaders, Kimbro said. But the same is not true of marine plants, which can’t outcompete the invasive algae that commonly plague their habitats. On the other hand, herbivory, or plant consumption by animals, is a strong controlling factor both on land and in the sea.

Of course, not all foreign species are problematic, as Kimbro pointed out. Corn is a good example: Though it’s grown all over the world, and we depend on its success for our own livelihood, it’s native to only a small area of Central America.

“Regardless of whether we’re talking about a good or bad invader, we want to know what allows them to succeed or what inhibits their success,” Kimbro said, adding that both are critical to maintaining healthy and economically sound ecosystems.