海角大神

Just off Highway 880 at the edge of Hayward, the cityscape changes abruptly. Businesses and parking lots give way to large swaths of pickle grass and pools of water stretching out to the eastern edge of the San Francisco Bay.听

On a recent sunny, windy March day 鈥� just before COVID-19 sent the Bay Area into lockdown 鈥� Dave Halsing stood on the trails at Eden Landing Ecological Reserve and pointed out what used to be old industrial salt ponds. He noted how they鈥檙e gradually being restored into a rich mosaic of tidal wetlands and other ecosystems in the South Bay Salt Pond Restoration Project.

Little by little, he explains, over 15,000 acres of salt ponds 鈥撎齦argely ecological dead zones that had been transferred from industrial companies to the state 鈥� are being brought back to functional ecosystems. They provide important habitat for species like the Western snowy plover and California least tern, add recreational trails for Bay Area residents, and provide flood protection for the San Francisco Bay 鈥� a needed adaptation in an era of rising seas. 鈥淚t鈥檚 inspiring but challenging,鈥� says Mr. Halsing, the executive project manager.

The work to restore the Bay Area鈥檚 tidal marshes is just one example of a strategy that has been gaining attention in the past few years from climate change experts. Often described as 鈥渘ature-based climate solutions,鈥� this strategy encompasses a wide range of conservation and restoration approaches involving trees, mangroves, soil, and marshlands.听

Many current projects 鈥撎齦ike the South Bay Salt Pond Restoration Project 鈥� have locally targeted goals: improved habitat for species or resilience to climate change-related events like hurricanes, floods, or fire. But investing in such approaches at a large scale has another potential benefit, too, say experts: harnessing the natural ability of trees, plants, and soil to store carbon.听

鈥淣ature figured out how to solve the toxic carbon dioxide problem 3 billion years ago when it invented photosynthesis, and we鈥檙e trying to invent similar processes now to solve carbon dioxide in the atmosphere. So why not use nature,鈥� explains Peter Ellis, a forest carbon scientist with The Nature Conservancy, who co-authored a landmark study听in 2017 showing that natural climate solutions could accomplish about one-third of the mitigation work required in the next decade to keep warming below 2 degrees Celsius.听

Could planting one trillion trees actually work?听

Those promoting natural climate solutions emphasize that it鈥檚 just one piece of a puzzle that also requires a major shift away from fossil fuels and carbon-based energy. But many experts are seeing these natural solutions as low-hanging fruit that have yet to be tapped at a large scale.听

In January, the World Economic Forum launched the ambitious One Trillion Trees initiative, with the goal of planting and conserving 1 trillion trees around the globe in the coming decade. Even President Donald Trump signed on.听

The initiative has received some criticism, even among climate activists, who worry it鈥檚 overly simplistic, takes emphasis off of the energy shift that needs to happen, and will encourage poorly conceived projects that might perpetuate other environmental issues.

And some climate experts have argued that the claims made by natural-solutions proponents in general are lofty and overly optimistic 鈥� that they couldn鈥檛 come close to reducing carbon dioxide at the magnitude some studies have found.听

But those debates, ultimately, are unproductive, says James Mulligan, a senior associate in the World Resources Institute鈥檚 food, forests, and water program. Climate solutions, he notes, aren鈥檛 a zero-sum game. Nature-based solutions won鈥檛 ever be enough on their own, says Mr. Mulligan, but they have some big upsides, particularly that most are relatively low cost, some have more bipartisan appeal, and many are 鈥渨in-win,鈥� with none of the 鈥渓osers鈥� that can be a byproduct of other strategies.听

鈥淭he question for me is: would this help? And the answer is yes,鈥� says Mr. Mulligan. 鈥淒o I think we can restore a trillion trees to the planet? Probably not. ... In the U.S., our analysis shows we could restore 60 billion trees to the American landscape.鈥� That, he says, would be a 鈥渢all order,鈥� but would remove about a half a gigaton of CO2 per year.听

鈥淭hat鈥檚 a meaningful wedge,鈥� he says. 鈥淎nd that鈥檚 just one nature-based solution.鈥澨�听

Protection before planting?

All trees 鈥� and all nature-based solutions 鈥� aren鈥檛 created equal. And many advocates stress that it makes sense to focus on the ecosystems with the most to offer, or the methods that yield the biggest dividends.听

鈥淲e need to protect first, to hold the line,鈥� says Mr. Ellis of The Nature Conservancy, explaining that he views good management of existing ecosystems as being even more important than restoration.听

Certain ecosystems, like mangroves and peatlands, are of vital importance to conserve, says Will Turner, senior vice president of global strategies for Conservation International. In those ecosystems, the soil stores so much carbon that losing much more of it in coming years would be devastating, he says.听

But to Dr. Turner, conservation and restoration are two sides of a coin, both necessary. Protecting critical ecosystems like tropical forests and mangroves that are being destroyed at a steady rate is crucial in terms of reducing current emissions, he says. But removing carbon dioxide already in the atmosphere is also necessary, if there is any hope of keeping warming below 2 degrees Celsius.听

鈥淲e have a long way to go before we have any technology that is capable of removing CO2 from the atmosphere at scale except trees,鈥� says Dr. Turner. 鈥淲e鈥檇 be foolish not to invest incredibly heavily in regrowing forests.鈥�

Despite all the potential of natural climate solutions, most of the examples being tried so far are at a relatively small scale.听

WRI鈥檚 plan for 60 billion trees planted in the U.S. over the next 20 years, Mr. Mulligan notes, would require about $4 billion a year in federal subsidies. But many of these efforts are 鈥渉appening at the pace and scale of the conservation sector,鈥� he says. And that figure,听while relatively modest in terms of government spending, is far beyond what the nonprofit community can handle.听

Dr. Turner, of Conservation International, agrees. What the conservation community has done well, he says, is shown how these projects can work, how technology can be used to monitor and verify emissions reductions, and how financial mechanisms can allow governments or corporations to invest in these strategies.听

Discovering an ecosystem in every backyard

Meanwhile, part of the beauty of nature-based solutions, Dr. Turner says, is that 鈥� while some may certainly have more payoff than others in terms of climate mitigation 鈥撎�鈥渢here is something that can happen anywhere. Every community has an option to protect a forest or grow a forest or protect a grassland, or to better manage grazing lands so you can get greater carbon stored in the soil.鈥�

And many of those solutions 鈥� like the marsh restoration taking place in the San Francisco Bay 鈥� offer significant local benefits that go far beyond potential emissions reduction: habitat for endangered species, cleaner air and water, recreation opportunities for residents, flood risk mitigation at a time of rising seas.听

In the Bay Area, emissions mitigation isn鈥檛 a real driver of the restoration work, and the carbon market for wetlands isn鈥檛 as robust as that for forests. But that doesn鈥檛 mean those benefits don鈥檛 exist, says Letitia Grenier, co-director of the Resilient Landscapes Program for the San Francisco Estuary Institute.听

In her role at the institute, Dr. Grenier looks for creative ways to harness the natural benefits of ecosystems in ways that work for both people and nature 鈥� and they are plentiful, she says.

鈥淥ne of the things climate change has shown us is that we live in ecosystems,鈥� says Dr. Grenier. 鈥淣ot only do we impact ecosystems, but our ecosystem impacts us.鈥� In many instances, she says, when she looks at, say, a large watershed, the system is essentially broken. Too many discordant elements have been introduced.听

鈥淪uddenly, our system is not working for us,鈥� says Dr. Grenier. 鈥淐limate change is creating the realization of that, and the opportunity to fix it.鈥�

Staff photographer Ann Hermes contributed to this report from Hayward, California.

This story was published as part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.

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