Forests Will Sequester Less Carbon in the Coming Decades. Afforestation Programs Could Change That.
A new report estimates that, over the next four decades, the rate of carbon dioxide stored by US land each year will fall by 21 percent—a finding that spells trouble for national carbon removal goals.
💡 What’s the story?
A new report released today by scholars at Resources for the Future (RFF) estimates that, over the next four decades, the rate of carbon dioxide stored by US land each year will fall by 21 percent—a finding that spells trouble for national carbon removal goals.
The United States aims to sequester over 1 gigaton of carbon dioxide-equivalent per year—a goal comparable to taking roughly 223 million passenger vehicles off the road each year. While afforestation programs could increase the amount of carbon dioxide stored by American lands, even a program that supports an unprecedented 90 million acres of new forests would not meet that national goal, the paper finds. To make up the difference, the authors suggest that investments in novel carbon sequestration technologies will be needed.
🌳 Why is this happening?
Between 1987 and 2017, market-driven changes spurred US forest growth. Over the span of 30 years, new forests expanded across an area the size of Kentucky—roughly 21 million acres. But new RFF modeling has found that, as these forests have aged, their average annual rate of carbon sequestration has naturally decreased from 0.89 gigatons of carbon dioxide-equivalent between 1990 and 1995 to 0.81 gigatons of carbon-dioxide equivalent between 2015 and 2022. This difference is equivalent to the carbon emissions of 18 million passenger vehicles.
Land use is also changing. As human settlement expands, particularly in the Southeast and Pacific Northwest, forest loss is contributing to the decline in carbon sequestration rates.
The authors emphasize that they expect this decline to continue under a business-as-usual scenario: between now and 2062, they expect US forests to sequester, on average, 0.73 gigatons of carbon dioxide-equivalent per year.
Historic and projected land carbon dioxide removal
“Forests take in less carbon year over year when they’re older as opposed to when they’re young and hungry to grow and outcompete their neighbors. Old forests, in fact, are in ‘stasis’ – they take in little, if any, net carbon. As the forests that used to sequester vast amounts of carbon age, we’re finding that the sequestration levels we saw in the early 2000s were not a new normal, but rather a peak.”
—David Wear, RFF Nonresident Senior Fellow
📈 How can we change the trend?
Aging forests and land use change mean that the rate of carbon sequestration is falling at a time when climate goals call for an increase. The report digs into a potential policy option to alleviate the decline: a massive federal program that would encourage the planting and regeneration of forests.
But such a program can only go so far, the report finds. Growing 3 million acres per year for 10 years—30 million acres total, and on the same scale as the largest conservation initiative ever funded by the US federal government—would create an additional 3.6 gigatons of stored carbon dioxide-equivalent compared to business-as-usual, a 12 percent increase, raising the average rate of sequestration to 0.83 gigatons of carbon dioxide-equivalent per year.
A larger program, which would entail growing 3 million acres per year over 30 years—90 million acres total—would create 8.5 gigatons of stored carbon dioxide-equivalent compared to business-as-usual: a 30 percent increase. Planting at this unprecedented scale would store an average of 0.95 gigatons of carbon dioxide-equivalent per year, which exceeds historical rates but still falls below US sequestration goals.
“The US has ambitious carbon removal goals. Even under the optimistic scenarios that we’ve modeled, our forests alone aren’t enough to get us there, although it could come close. This means that as a nation, we’re going to need significant investment in afforestation and developing technologies to pull carbon out of the air.”
—Matthew Wibbenmeyer, RFF Fellow
🔎 How do we know?
The report authors, RFF Nonresident Senior Fellow David Wear and RFF Fellow Matthew Wibbenmeyer, used RFF’s new Carbon and Land Use Model (CALM) to conduct their analysis. The model first estimated “business-as-usual” carbon sequestration projections on nonfederal land based on land use changes and other metrics. They then predicted which areas are most likely to switch to forests based on historical patterns of change, and how afforestation programs could change the status quo.
This report is the first published use of the CALM model, which RFF scholars designed to predict the effects of land use change on carbon dynamics.
📚 Where can I learn more?
To learn more, read the report, “Prospects for Land Sector Carbon Dioxide Removal in the United States,” by RFF Nonresident Senior Fellow David Wear and RFF Fellow Matthew Wibbenmeyer.
Resources for the Future (RFF) is an independent, nonprofit research institution in Washington, DC. Its mission is to improve environmental, energy, and natural resource decisions through impartial economic research and policy engagement. RFF is committed to being the most widely trusted source of research insights and policy solutions leading to a healthy environment and a thriving economy.
Unless otherwise stated, the views expressed here are those of the individual authors and may differ from those of other RFF experts, its officers, or its directors. RFF does not take positions on specific legislative proposals.
David N. Wear
Nonresident Senior Fellow; Director, Land Use, Forestry, and Agriculture Program
David Wear is a nonresident senior fellow and the director of the Land Use, Forestry, and Agriculture Program at RFF.
Report — Jun 21, 2023
Prospects for Land Sector Carbon Dioxide Removal in the United States
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