Many government commitments to fight climate change hinge on planting huge numbers of trees in hopes that the plants will remove carbon dioxide from the atmosphere and store it in their trunks. Scientists have criticized the suggestion that mass tree planting could be a climate change panacea, but a new study suggests there may not even be enough seeds to reach the lofty reforestation goals of initiatives such as the World Economic Forum’s one trillion tree campaign.
In the United States, the "Trillion Trees Act" proposed planting 24 billion trees over the next 30 years. A 2020 analysis from the World Resources Institute stated that there was ample space to achieve 60 billion new trees by 2040, if all suitable land across the country was reforested without reducing food production.The new study was published last month in the journal Frontiers in Forest and Global Change.
The U.S. would need to double its current seedling production—and then some—to plant roughly 30 billion trees, which is the amount the authors estimated would fit on the lower 48 states' natural and agricultural lands, reports Kyla Mandel for National Geographic.
“You can’t plant a tree until you grow it. And you can't grow it in the nursery until you have the seed,” Joe Fargione, science director for The Nature Conservancy's North America Region and the study’s lead author, tells National Geographic.
Per the study, U.S. seedling production is currently around 1.3 billion a year, which means adding 30 billion trees by 2040 would require increasing annual production by 1.7 billion seedlings, a 2.3-fold increase that would raise total production to 3 billion baby trees.
“There were increasing public calls for dramatically scaling up reforestation,” Fargione tells Jesse Klein of Wired. “The people that work in the industry were aware that would be hard to do because of the supply chain challenges. But most people outside the industry weren’t.”
In a statement, the researchers say boosting seedling production will require expanding tree nurseries, increasing the industry’s workforce, increasing seed collection and storage capacity, and improving pre- and post-planting practices.
According to National Geographic, expanding seedling production will take significant investment, but the levels of production necessary aren't unprecented. Production in the U.S. actually peaked in the late 1980s at more than 2.6 billion a year. That total got slashed by the 2008 recession, and Fargione tells National Geographic only a third of the nurseries that weren’t forced to close down are currently operating at full capacity. This means there’s an opportunity to increase production without immediately adding new nurseries. But to reach the three-billion-seedling-a-year minimum identified by the paper, the researchers say all existing public and private nurseries would need to expand their operations while also maxing out their production capacity.
Meanwhile, the U.S. Forest Service has seen budget cuts and has been kept so busy fighting forest fires that it’s only been able to reforest about 20 percent of national lands in need of replanting, according to Wired.
Then there’s seed collection, which is a more complicated and laborious process than one might think, and requires someone with sufficient training to navigate its nuances.
“They need to get a seed from that geographic area, from the right elevation, from the right species of tree, and grow those seeds in a nursery for a year or plus,” Marcus Selig, vice president of field programs at the National Forest Foundation, tells Wired. “Then they take the seedlings back to that exact place to regenerate the trees. It’s just a really involved process.”
Whether predictable, long-term funding from the public or private sector that would be necessary to ramp up seedling production will materialize remains to be seen. Increasing protections for existing forests or even expanding their boundaries shouldn’t be overlooked, Karen Holl, an environmental scientist at the University of California, Santa Cruz who wasn’t involved in the study, tells National Geographic.
Finally, even if the U.S. can increase its seedling production and put those trees in the ground, there needs to be a plan for making sure a large percentage of them survive. Fargione tells Wired, on some projects, 85 percent of seedlings die within a year of being planted.
“A plant-and-walk-away approach doesn’t work,” he tells Wired.
It takes time, money and expertise to ensure that the right trees are planted in the right locations and given the care they need to thrive, explains Greg Edge, a forest ecologist with the Wisconsin Department of Natural Resources’ Forestry Division, to National Geographic.
“You can't just stick a tree in the ground and come back in 100 years and have a forest.” Edge says. “We don't want to just waste our time sticking a seedling in the ground that'll die."