Protecting Coral Reefs

It may not be news to you that coral reefs—the world’s most diverse ecosystems—aren’t doing so well in the face of climate change. But it’s time to change the old refrain from alarm to action. In this week’s Nature, an international group of scientists publish the first data on how we can start to restore these fragile fisheries in as little as 35 years.

In previous Science Today articles, we’ve focused on the negative effects of climate change and some of the ways corals are adapting to new, warmer environments. M. Aaron MacNeil of the Australian Institute of Marine Science (and his colleagues) aren’t out to scare the world into conservation; instead, his team wants to find “tangible solutions that promote recovery and enhance ecosystem functions.” In this case, they mean fishing.

In addition to their beauty, coral reefs feed millions worldwide. Top predators—the fish, sharks, and whales that eat all the smaller things protected in coral reefs—are coming into view as essential elements for the overall health of an ecosystem. But how much fishing can a coral reef take before the food web disintegrates? MacNeil and his coauthors looked at the overall biomass of fish in reefs, as well as the diversity (of size and diet), and measured how depleted local fisheries have become.

“The status of reef fish... varied considerably by locality and whether there were management restrictions on fishing activities,” wrote the researchers. Some fisheries were completely healthy, such as those associated wiht the remote Easter and Pitcairn Islands. But in Papua New Guinea and Guam, the authors found only 10 percent of the baseline biomass, “a fisheries reference point assumed to indicate collapse.” Not good news.

MacNeil and colleagues aren’t despondent about these troubling findings: using data from previously protected areas and coral reefs where fishing practices are managed, they were able to extrapolate how long it might take for these reefs to recover. And here’s the good news! In most cases, the expected time to recover 90 percent of original biomass is only 35 years, and when the reef is heavily depleted, just under 60 years. Turning around the health of coral reefs is achievable within our lifetimes!

And while marine protected areas (where no fishing is allowed) are an important part of the recovery equation, the scientists found that even partial fishing restrictions can effectively allow reefs to rebound. Instead of simply advocating for a worldwide halt on all fishing in coral reefs—a scenario that would impose hardships on millions of people worldwide—MacNeil and his co-authors assert that a variety of managed approaches have already been successful in both developed and developing countries.

That’s also good news: marine reserves that prevent all fishing “can be untenable where people depend heavily on reef-based resources.” But banning certain types of fishing gear, or the harvest of specific species, can protect fish populations and reef ecosystems—and regional livelihoods and food supplies. As MacNeil told Pacific Standard:

“We found that any kind of restriction had a positive effect in terms of maintaining the ecosystem,” MacNeil says, “and that’s a really big deal because all of a sudden you’ve gone from a one size fits all [management technique] to a range of options for people.”

Image: Nick Graham