Protect fish to produce more food and reduce greenhouse gas

Menhaden catch, destined for use as fertilizer and pet food. (Wikimedia Commons)

by Tim Radford
Climate New Network, March 25 2021

Scientists have identified a sure way towards more profitable fishing: don’t do it. Protect fish and leave as much of the seas as possible untouched.

To convert the right stretches of the blue planet into marine sanctuaries would actually deliver bigger hauls than any uncontrolled harvests could promise. It could also protect marine wildlife and reduce greenhouse gas emissions to the atmosphere.

“Ocean life has been declining worldwide because of overfishing, habitat destruction and climate change. Yet only 7% of the ocean is currently under some kind of protection,” said Enric Sala, of the Pristine Seas project at the National Geographic Society.

“In this study, we’ve pioneered a new way to identify the places that − if protected − will boost food production and safeguard marine life, all while reducing carbon emissions. It’s clear that humanity and the economy will benefit from a healthier ocean. And we can realize those benefits quickly if countries work together to protect at least 30% of the ocean by 2030.”

No to exploitation

He and 25 other scientists from the US, Canada, France, Germany and Australia report in the journal Nature that they have devised a planning framework and identified regions of ocean that would benefit most from status as Marine Protected Areas, or MPAs.

Right now only around 2.7% of the high seas are fully or highly protected, and in all 7% have been designated or proposed as suitable for such status. The scientists argue that to safeguard their proposed areas could offer safety for 80% of marine species, ultimately add eight million tonnes more to the global catch than any uncontrolled trawling could offer, and prevent the release of more than a billion tonnes of carbon dioxide a year − simply by preventing disturbance of the sea floor.

They see an enormous gain if even 21% of the ocean is protected, and they want to see 30% of the global ocean undisturbed and valued as a conservation resource by the year 2030.

The argument that humans can profit more from conserving the wilderness than by ruthlessly exploiting it sounds radical. But it has been made again and again. On land, separate research teams have found repeatedly that forests and wetlands deliver a higher net return in the long term, and to the greatest number of people, than mining, felling or farming can offer.

And it has been the same story afloat: world fish catches would benefit from protected areas; fishing itself would become more dangerous and with lower returns in a regime of uncontrolled global climate change; and a reduction in the rate of global heating would pay off in richer marine harvests.

Diplomats and scientists from 190 nations will meet in Kunming in China this year for a conference of the UN Convention on Biological Diversity. The US, Canada, the European Commission and other nations have committed to the goal of protecting 30% of the planet by 2030.

But the implication of the latest study is that such declarations are only as good as the effort to realize them that sponsor nations are prepared to make. Most of the proposed protected stretches of sea are within the 200-mile exclusive economic zones of coastal nations; others − the Mid-Atlantic Ridge, for instance, and the Southwest Indian Ridge between South Africa and Antarctica, are governed by international law.

The researchers’ proposals would require a ban on bottom trawling, in which heavy nets scour the submarine ooze. The carbon dioxide released into the ocean from this practice alone is higher than emissions from global aviation; higher even than most countries’ annual carbon emissions.

More is worse

“The ocean floor is the world’s largest carbon storehouse. If we’re to succeed in stopping global warming, we must leave the carbon-rich seabed undisturbed,” said Trisha Atwood of Utah State University, one of the authors.

“Yet every day, we are trawling the seafloor, depleting its biodiversity and mobilizing millennia-old carbon and thus exacerbating climate change. Our findings about the climate impacts of bottom trawling will make the activities on the ocean’s seabed hard to ignore in climate plans going forward.”

The overall argument the researchers put to the world’s great fishing nations is a simple one: the worst enemy of successful fishing is overfishing. “It’s simple: When overfishing and other damaging activities cease, marine life bounces back,” said Reniel Cabral of the University of California Santa Barbara, another of the signatories.

“After protections are put in place, the diversity and abundance of marine life increase over time, with measurable recovery within reserves occurring in as little as three years. Target species and large predators come back, and entire ecosystems are restored within MPAs. With time, the ocean can heal itself and again provide services to humankind.”