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A forest landscape in Colorado.
A forest landscape i A forest landscape in Colorado. © Mark Godfrey/The Nat

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New Study Finds Barriers to Accelerating Reforestation

1.7 Billion More Trees Needed to Meet Climate, Jobs, Fire Recovery Goals

  • Lindsay Schlageter

In order to accelerate reforestation in the United States, the entire pipeline for tree planting would need to be scaled up.  The nation’s tree nurseries need to increase seedling production by an additional 1.7 billion each year, a 2.4-fold increase over current nursery production. These numbers, taken from a new study, show the promise of increased reforestation as a way to fight climate change, create jobs, and recover from catastrophic wildfires.

Across the U.S., large-scale reforestation has been identified as a key natural climate solution to increase carbon sequestration as a complement to ongoing work to decrease greenhouse gas emissions from fossil fuel use.

The study, published in the science journal Frontiers in Forests and Global Change, was co-authored by 18 scientists from universities, nonprofits, businesses, and state and federal agencies.

In Colorado major wildfires on the Front Range since the 1990s have left large patches of previously forested landscape barren, with few if any mature, cone-bearing trees surviving. In these areas, known as burn scars, the “the lack of a seed source creates a barrier to natural regeneration for some conifer trees, like ponderosa pine.” commented Dr. Teresa Chapman, a scientist at The Nature Conservancy in Colorado and one of the co-authors of the study.

As a result, reforestation of burn scars presents a clear opportunity as a natural climate solution in Colorado, especially as wildfire size, frequency, and severity are predicted to further increase with warming temperatures and increased chances of drought.

To illustrate the prospects for increasing reforestation capacity in the U.S., the researchers of the study identified 64 million acres of opportunity on natural and agricultural lands, nearly half of the total reforestation opportunity. Accounting for different planting densities by region, it would require 30 billion trees to reforest these lands. This equates to 1.7 billion more tree seedlings produced each year for this land to be reforested by 2040.

To achieve this large increase, investment is required across the entire reforestation “pipeline.” Additional investment would be needed to expand capacity for seed collection, seed storage, tree nursery expansion, workforce development, and improvements in planting practices.

For numerous tree species in the West, such as ponderosa pine, there are additional considerations for expanding reforestation. For example, ponderosa pine has years of mast seeding, when seed collection can be easily achieved, on a decadal time scale.

Even if seedling production can be greatly increased, many burned areas suitable for reforestation are remote and difficult to access. In Colorado, The Nature Conservancy is working with partners to test new ways to reforest less-accessible areas through direct sowing of seeds, which is not simply a matter of scattering seeds on the soil surface. TNC is also testing the timing of seed distribution, novel seed activation methods, and different types of seed coatings and seed pellets to identify how best to achieve high germination and survivorship rates. If successful, this effort could also relieve some of the pressure on tree nurseries since seeds could take the place of seedlings in some settings.

 “Direct seeding could complement traditional tree planting efforts, lowering the cost of reforestation in those areas far from roads and unlikely to be planted using traditional means,” said Catherine Schloegel watershed forest manager for The Nature Conservancy in Colorado, who is leading these efforts. “By focusing our research on testing coatings and seed pellets, we aim to protect the seeds from predation and be more flexible in terms of suitable weather for planting.”

In December 2020 and early 2021, scientists distributed seeds and pellets on the burn scars of the 2000 Bobcat Gulch fire near Fort Collins and the recent 2020 Calwood fire near Boulder. Monitoring will reveal if seeds germinate and tree seedlings can establish on these challenging sites.

“By working together with our partners to increase seed collection and tree and seed planting, we can make great strides towards increasing our own reforestation pipeline and the benefits these trees will provide for communities and wildlife,” added Schloegel.

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 76 countries and territories: 37 by direct conservation impact and 39 through partners, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit www.nature.org or follow @nature_press on Twitter.