Amid pressures like overfishing, fluctuating water temperatures and rising ocean acidity, the planet’s coral reefs have been taking a beating. But there may be some good news: A recent survey of data on more than 2,500 of the world’s coral reefs has found that, while fish abundance in some spots is worse off than expected, areas are far healthier than expected — and scientists may be able to pinpoint what’s causing the difference.
Joshua Cinner, a professor of environmental social science at James Cook University in Australia, collected data on the health of reefs as measured by the total biomass of the fish they supported. He paid particular attention to the outliers — that is, the “bright spots” where fish life seemed far more abundant than models would have suggested, as well as the “dark spots” where conditions were far worse than researchers might have predicted.
Taking the top 50 outliers among the world’s reefs, he found 15 bright spots and 35 dark spots. To his surprise, Cinner found that the bright spots were not all in pristine, remote and unfished waters — and that many were in populated areas with a substantial amount of fishing.
The difference was that the people in the bright spots were carefully managing the reef, either by local tradition or by adhering to government regulations that limit overfishing. For example, one of the bright spots is Karkar island in Papua New Guinea. There, the indigenous people have long had customs that limit who is allowed to fish, as well as when they can fish an area. About a third of the time, patches of water are left unfished.
The local people don’t do this for the health of the reef, but because they noticed that constant fishing makes the fish wary of fisherman, and they stay just far enough away to be out of spear-range. By holding back in some areas, the practice allows more fish to flourish, which in turn contributes to a healthier reef.
In the dark spots, by contrast, the availability of a fish freezers — which allowed for larger numbers of fish to be stockpiled — and the use of large nets that drag the bottom of the ocean while collecting huge numbers of fish, both contributed to unhealthy conditions.
Cinner says the next step is to analyze the bright and dark spots in more detail to produce a portfolio of the best and worst practices, so they can be fashioned into reef management rules for local governments. Fisheries may be coaxed to sign on to “best practice” routines and given certificates of sustainable practices that they can use in advertising
As it is now, governments have been trying to keep reefs healthy by creating huge marine sanctuaries where fishing is not allowed or is limited. But these sanctuaries tend to be established in remote areas. Now, it may be possible to give reefs some protection systematically, even in areas where human populations rely heavily on the reef.
Of course, the greatest danger to coral reefs remains climate change and warming waters that cause bleaching events, Cinner says. But while working on social policies that reduce carbon emissions that are the real problem, we may be able to do something useful for the coral reefs and their human dependents.
“You can’t climate-proof a reef,” Cinner said, “but bucking that trend, we may have some secrets of what we can do that will be useful.”