Reforestation is critical to meeting Paris climate change accord targets, researchers say

'Urgency of climate crisis' is seen as demanding push for vast reforestation across U.S.

Climate change experts accept that reducing greenhouse gas emissions – even doing so substantially – won’t be sufficient for limiting atmospheric warming to the 2°C (3.6°F) goal of the Paris Climate Agreement. And with carbon capture technologies years away from maturity and widespread commercialization, one option is to take advantage of proven nature-based systems for sequestering carbon.

That is the central message of a widely discussed recent article in the journal Science Advances. America’s trees, soil, and wetlands each year capture around 11 percent of the nation’s emissions, according to EPA. The study’s researchers calculate that they could be harnessed to sequester up to 21 percent of net annual emissions of the U.S. .

In particular, the study authors identified reforestation – replanting historically wooded settings that no longer have forests – as the natural solution with the most potential to capture additional carbon. They found that actions like improving tree plantations, managing cropland nutrients, and restoring tidal wetlands also offer promising mitigation opportunities, but on a much smaller scale.

'A forgotten solution to climate change,' massive reforestation across U.S. is seen as critical to reducing climate change risks.CLICK TO TWEET

“Natural climate solutions have really been a forgotten solution to climate change,” said Joe Fargione, the paper’s lead author and the head scientist for North America at The Nature Conservancy, a global conservation nonprofit. “Because the climate crisis is so urgent, we need to look at all the possible solutions, and that should include reforestation.”

Carbon pricing and amenity value co-benefits

Since publishing the research last fall, Fargione said in a phone interview, he’s heard from people curious about ways to reach reforestation’s climate mitigation potential. His response: Carbon pricing is an important part of the solution, but co-benefits could also spur action.

“For example, planting trees in cities is something that, if you were just looking at it from cost per ton of carbon stored, is relatively expensive. But that’s not why people do it; they do it because they like living near trees,” he said. “The amenity value of forests and trees is really high, so I think there’s a lot of opportunity to build political momentum around having more trees.”

A survey of The Nature Conservancy’s reforestation work showed that much of it is associated with water quality co-benefits. For instance, planting trees after a forest fire helped prevent drinking water contamination in Santa Fe.

Lands deforested as a result of insect infestations, deer overpopulation, or other factors unrelated to human land-use decisions, Fargione said, also offer what he characterized as “low-hanging fruit.”

“You can see communities investing in protecting their watersheds for drinking water protection and addressing the issues with understocked lands,” Fargione said. “And those are near-term opportunities that can be focused on even in advance of a price on carbon.”

Mapping reforestation opportunities

Susan Cook-Patton, a co-author of the Science Advances paper and Fargione’s colleague at The Nature Conservancy, has spent much of the past year working to help state-level decisionmakers decide which reforestation opportunities make the most sense in their unique circumstances.

Her work builds on a map of re-forestable land that was developed for the natural climate solutions study. To create the map, researchers used government data sets to identify historically wooded areas around the U.S. where trees have been lost, then subtracted settlements, roads, and food-producing land to avoid conflicts with critical human infrastructure.

The resulting picture demonstrated the nation’s tremendous reforestation potential, but was not intended to identify shovel-ready projects. When the researchers examined the sites identified in greater detail, they found a variety of existing land uses, from federal properties to highway medians and people’s backyards. Clearly, some sites would be easier to fill with trees than others. “You might be able to reforest the post-burn landscapes,” Cook-Patton said, “whereas something like a golf course – unless people decide they want to prioritize climate over golf – it’s going to be way too cost-prohibitive to try to restore that land.”

Her current project aims to develop toolkits of different data layers that states can use to analyze potential reforestation sites, taking into account cultural and social variables in addition to ecological and financial considerations.

“We’re trying to come up with more of a menu-type approach where we can say, ‘OK, for a given state, here’s where the most area is that you could potentially reforest; here’s how much we think it might cost; and here are additional benefits that you might get out of that.'”

Good infrastructure investment … not ‘kind of cute’

For Jad Daley, the president and CEO of the nonprofit conservation organization American Forests, one primary barrier to large-scale reforestation is a lack of awareness about the critical services trees provide. In addition to helping provide clean water and oxygen, forests absorb massive amounts of carbon. “Our forests and forest products are already delivering a 15 percent carbon capture for the U.S. every single year,” he said, taking into account carbon stored in tree-derived products like wood and paper. “They’re a big, big piece of the puzzle. And if we reforest America, we could make them an even bigger piece of the puzzle.”

Recently, much of Daley’s work has focused on informing members of Congress about reforestation, explaining how relatively small investments can deliver sizeable benefits for the nation. Based on positive feedback from Democrats and Republicans alike – including, he said, from some of America’s most conservative lawmakers – he’s optimistic that federal support will increase. “It’s a matter of seeing paying for reforestation with public funds as being a good infrastructure investment,” he said, instead of just “kind of a cute solution.”

He also sees movement at lower levels of government. American Forests is working with The Nature Conservancy and other groups as part of the Natural and Working Lands initiative of the U.S. Climate Alliance, which helps states scale up their climate actions. As the 22 member states formulate their plans, reforestation has emerged as a priority, and a number of creative strategies are being developed to fund it. “I think we can really count on these states to be rapidly ramping up and becoming real drivers for reforesting America,” Daley said.

‘… really our only hope’?

One frequently raised question is whether reforestation might create new carbon sources if wildfires, drought, or other climate-related threats damage young trees.

This line of reasoning is flawed, said Joe Fargione. Reforested lands hold only a small portion of the carbon already contained in the landscape, all of which is at risk as the planet gets hotter. But a major reforestation initiative would reduce the chance of catastrophic warming occurring in the first place, he maintains.

Experts now understand how to make forests more climate-resilient by means of improved tree selection and planting techniques. But for Fargione, the issue comes down to more a fundamental concern.

“We have a rapidly closing window to achieve a world that everyone agrees we want, and the only way to get there is to invest in natural climate solutions, on top of rapidly transitioning the energy sector,” he said. “So I think the fact that it might not work doesn’t mean we shouldn’t try. It’s really our only hope.”