First, the Good News

A new study shows simple fishing restrictions can bring coral reefs back to life—but only if we stop emitting so much carbon dioxide.

April 09, 2015

Photo: Klaus Stiefel/Flickr

Biodiversity on the world’s coral reefs is suffering badly, but simple restrictions on fishing could help restore most of these ecosystems in just a few decades, according to research published this week in the journal Nature. I love this study for its focus on solutions, which are too often an afterthought in the doomsday field of ecological research. That’s not to say there’s no doomsday stuff—ecological research, like a superhero movie, needs a bit of darkness.

M. Aaron McNeil of the Australian Institute of Marine Science and his colleagues started by estimating the weight of fish swimming around coral reefs in pristine stretches of ocean—areas protected by law or so remote that humans rarely bother to fish them. In these relatively untouched stretches of sea, coral reef ecosystems contain about one ton of fish per hectare. They used that statistic as a baseline to estimate what coral reefs could be like without the influence of fishermen.

The researchers then looked at the fished coral reefs and found that the overwhelming majority of them—83 percent, to be precise—are missing at least half of their natural fish numbers. One in four of those reefs have below 25 percent of their historic fish density, a threshold that previous research suggests represents the early stages of an ecosystem’s death spiral. Coral reefs near Papua New Guinea and Guam have lost 90 percent of their fish biomass, which indicates near-total collapse.

The most effective solution is to ban fishing in and around the suffering coral reefs. According to McNeil’s data, that could bring the ecosystems almost back to health in approximately 35 years, which means your grandchildren could be born into a world with robust coral reef ecosystems, bursting with color and life. (Unless you’re already a grandparent. Congratulations, by the way.)

Unfortunately, comprehensive fishing bans aren’t always practical. Many of the world’s reefs are near developing countries, where exploding populations and poverty make it nearly impossible to stop people from overfishing their coastal waters. Even for those heavily stressed regions, though, there’s some good news. The study shows that areas with basic restrictions have 27 percent more fish than ecosystems with no limitations. Doing a little bit is far more effective than doing nothing.

What sorts of restrictions are we talking about? Equipment limitations are a good start, whether the fishing is taking place on a reef or in the open ocean. Consider the vacuum pump, which allows fishermen to suck fish by the thousands into waiting nets. It’s like something out of a piscine nightmare. Other damaging techniques include bottom trawling (dragging a weighted net across the sea floor) and long-lining (fishing with 60-mile lines that contain thousands of hooks), blast-fishing with dynamite, spearfishing, and spraying a cyanide solution into the water to stun fish (typically for the aquarium trade). Restricting those methods would help give reef biodiversity a boost, in addition to rules on fishing at-risk species and seasonal bans.

Overfishing, however, isn’t the only threat facing reef ecosystems. Ocean acidification, a result of carbon emissions (that are much more difficult to manage than fishermen), is already killing coral species around the world. Warmer water temperatures from climate change and runoff pollution can also lead to coral bleaching, an often fatal condition.

In the Caribbean, coral populations have declined more than 50 percent since the 1970s, and a recent analysis found that most of the region's reefs could disappear in just two decades. Four years ago, reef expert Peter Sale predicted that all of the world’s coral reefs could disappear entirely by the end of this century. Fishing restrictions alone can’t save these ecosystems. We have to stop carbon pollution as well—and fast.

There I go again with the doomsday talk. I’ve got to stop reading so many studies.


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