Creating big, well-protected marine reserves may be among the best hedges humanity can take to counter climate change-driven disruptions now and in the future, according to a new study by an international team of researchers.

If they are well-protected, large enough, carefully sited and supported by local communities and the general public, these areas can blunt the effects of five marine transformations that are already happening due to the buildup of carbon dioxide in the atmosphere: diminishing oxygen levels, ocean acidification, rising seas, increasingly severe coastal storms and the shifting distribution of ocean plants and animals as they seek livable water temperatures.

But with only about 3.5 percent of national waters in some form of reserve, and only about half of those areas strongly protected from fishing and degradation, the world is far from conserving enough of the global ocean to assure those benefits. “Marine reserves will also help insure against inadequate management both in national waters and beyond national jurisdiction … and ensure that we do not make scientific advances through the belated realization of what we have lost,” the researchers concluded.

“We’re paraphrasing, in a slightly more scientific way, Joni Mitchell – who said, ‘You don’t know what you’ve got till it’s gone,’” said lead author Callum M. Roberts, a professor of marine conservation at the University of York in the U.K.

“One of the things that we are understanding about the world is just how much people have changed it, and those changes have led to the loss of many species and habitats,” he added. “Over time we’ve belatedly realized, for example, that coastal habitats are really important, that they protect coastlines, that they provide a whole range of useful values to humanity as well as sustaining biodiversity.”

Once habitats like these are destroyed, he said, “you’ve got two options. One is to rebuild them or one is to just regret the fact that they’re no longer there.”

Roberts’ team analyzed and compiled the findings of 145 peer-reviewed scientific studies on marine reserves to learn how such areas might affect the speed and scope of climate change. The results were published Monday in the journal Proceedings of the National Academy of Sciences as the United Nations Ocean Conference got underway in New York City to work out ways to restore ocean health – in part, by protecting at least 10 percent of the ocean in marine reserves by 2020.

One benefit, the researchers found, was that marine reserves can help restore populations of fish that excrete carbonates in near-surface waters. These additions may increase alkalinity and buffer those waters against the chemical changes caused by high carbon dioxide concentrations. “Fish produce in their guts these kinds of nodules of high-calcite carbonate,” Roberts said. “When that stuff is excreted, which it is every time they poop, it will dissolve in the sea and produce local decreases in ocean acidity.”

A bigger network of large, strongly protected reserves would also help more fish populations recover from overfishing, according to the study, stemming some future losses in species diversity. Rising global temperatures are already heating up the ocean’s top layer and reducing surface-mixing with cold lower waters, a process that is crucial to distributing nutrients in the ocean, noted Roberts.

“We are seeing that ocean layer becoming more stable, and more nutrient-starved, as a result of warming. That’s going to reduce ocean productivity,” he said. “We’ve done a pretty good job of reducing ocean productivity ourselves by fishing … one way that you can offset an expected future decline is to address the past declines that have been caused by us. And that means by rebuilding populations by establishing marine reserves and providing refuges where fish stocks can rebuild.”

A bigger network of large, well-managed marine protected areas would also provide “stepping stones” and “safe landing zones” for species on the move due to shifting temperatures, oxygen levels and acidity, as well as possibly helping species that cannot shift their ranges, the study noted. This would help preserve marine food webs, which are crucial to supporting the fisheries upon which hundreds of millions of people worldwide depend for their food and livelihoods.

Leaving these areas undisturbed by industrial fishing gear, such as bottom trawlers, would also maintain some of the ocean’s capacity to store carbon in seafloor sediments and plant life.

The study highlights the United States’ Papahānaumokuākea Marine Reserve National Monument, a 583,000 square mile (1.5 million square km) preserve in the northwestern Hawaiian Islands, as a “strategic refuge for coral reef ecosystems that may be forced poleward, because constraints on migration, such as acidification, the availability of suitable bottom habitat and dispersal, are few here.”

The second-largest fully protected marine area in the world, and home to around 7,000 known species, Papahānaumokuākea is one of several national monuments that the Trump administration recently targeted for review.

Many conservationists have criticized the move as a prelude to allowing fishing and mineral mining within the reserve. Still, Matt Rand, the director of the Pew Bertarelli Ocean Legacy Project, which provided funding for Roberts’ work, said he believes that the federal review “will indicate clearly that there was strong scientific support for the reserve, there was overwhelming public support for the reserve, there was political support for the reserve.”

Weakening the status of any marine reserve, but especially one as large and strongly protected as Papahānaumokuākea, would take both the U.S. and the world in the wrong direction, Rand said. “Most recent analyses indicate that between 30 and 40 percent of the ocean needs to be in some form of marine protection, for the greatest biological benefit to the ocean.”

“We have a ways to go for sure,” he said. “But we have been making exponential progress. In 2006, marine reserves of this scale, of over 200,000 square kilometers in size, were not even talked about. Now we’re talking about marine reserves that are over 1 million square kilometers in size.”

The biggest barrier to progress at this point is not political resistance, said Rand, who is among the thousands of activists, government representatives, scientists and members of nonprofit and business groups attending the first-ever U.N. Ocean Conference. Rather, it is recognition by the public that reversing ocean degradation is a crisis on a par with climate change.

“Just like any movement globally, you need public will to drive large-scale transformation,” he said, adding that the study will help many people grasp that the health of the ocean is a crucial component of acting on climate change.

“For a long time we’ve talked about the ramifications of marine reserves for biological reasons,” said Rand. “Now we’re starting to marry those two topics, and hopefully that means we’ll see some traction in the ocean space.”