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A trillion trees could cool the planet. But where to get them? There’s a massive disconnect.

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A trillion trees could cool the planet. But where to get them? There’s a massive disconnect.

Scientists audited the capacity of U.S. nurseries to grow enough seedlings for ecologically-minded tree planting campaigns. The results were not pretty.
August 9, 2023

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Everyone, it seems, wants to plant trees. Environmental groups have a goal of a trillion trees. Saudi Arabia wants to plant 10 billion. China has pegged the number at 88 billion. In the U.S., the 2021 federal infrastructure law opened the door to plans for 1 billion new trees within a decade.

But there’s a critical question that’s often overlooked: Where are the trees going to come from?

At least in the northern United States, the nursery system needed to crank out all these plants is profoundly unprepared for the job, a group of scientists is warning.

“Trees are this amazing natural solution to a lot of our challenges, including climate change. We urgently need to plant many millions of them,” said Tony D’Amato, a forest ecologist and head of the University of Vermont (UVM) forestry program. But “we are woefully underserved by any kind of regional or national scale inventory of seedlings to get the job done.”

In just one illustration of the shortcomings of the existing system, when D’Amato and his collaborators surveyed the more than 50 industrial-sized nurseries in the central and eastern parts of the northern U.S., they found just 800 ecologically important red spruce seedlings for sale from two nurseries in 2022—enough to plant about a hectare of land, the scientists reported July 31 in the journal BioScience.

 

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The team of scientists, which included federal U.S. Forest Service researchers, conducted what is essentially an audit of the nursery system, ticking off a number of shortcomings that could hobble tree planting initiatives.

The nation’s nursery infrastructure is aging and dwindling. The U.S. Department of Agriculture (USDA), which houses the U.S. Forest Service, once operated 59 nurseries. Today it has six. Seedling production in the northern U.S. fell by more than half between 2012 and 2020, the researchers found. By one estimate, nursery production will need to more than double to meet targets in the U.S.

The seedlings grown at nurseries are typically robust species sought for commercial forestry such pine trees or a few hardwoods like the northern red oak. Overlooked are the diverse climate-change adapted species needed for ecological restoration such as red spruce and bitternut hickory.

“The number of seedlings is a challenge,” said Peter Clark, a UVM postdoctoral researcher and forest ecologist who was the paper’s lead author. “But finding the diversity we need to restore ecologically complex forests — not just a few industrial workhorse species commonly used for commercial timber operations, like white pine — is an even bigger bottleneck.”

Add to that, efforts to grow trees best evolved for local conditions or for a variety of different climate scenarios are sabotaged by poor record keeping and a narrow range of seed sources, the scientists report. For instance, in 2022, red oak seedlings at nurseries originated from less than a third of the “seed zones” where the tree is found. Those zones are based on different ecological regions and how cold the temperatures get.

“People want trillions of trees,” said Clark. “But often, on the ground, it’s one old farmer walking around to collect acorns. There’s a massive disconnect.”

There are ways to fix the problem, say the scientists. But it sounds both costly and complicated. It includes investing in new nursery infrastructure, updating policies to give more weight to the ecosystem benefits of various trees, recruiting a new generation of people to work at nurseries, setting longer-term seed production plans to give nurseries more certainty, improving paperwork systems to track seed sources and beefing up monitoring to see how different seed stocks fare once they are in the ground.  

With ambitious targets and short time frames for many tree planting campaigns, it could be a big ask to make such reforms fast enough. Perhaps people trying to fix the nursery system and plant trees will need to take a few hints from the trees they are trying to raise: It can take a while to get big so be patient, but start growing now.

Clark et. al. “A lack of ecological diversity in forest nurseries limits the achievement of tree-planting objectives in response to global change.BioScience. July 31, 2023.

Image:  Photo by Markus Spiske/Pexels

 

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