Trees and Forests as Natural Climate Solutions
This training reviews the need for approaches to remove and sequester carbon from the atmosphere, the role trees and forests can play, and the other benefits that those solutions provide.
Background on the need for carbon sequestration
We can think of Earth’s atmosphere as a bathtub, and greenhouse gasses are equivalent to the water filling the tub. The tub is already overflowing and beginning to cause increasing damage to the floor and the rest of the bathroom as the water spreads, like the worsening extreme weather damages resulting from Earth’s rapidly changing climate.
To limit the damage, there are two main categories of solutions. First, we need to rapidly turn down (and eventually turn all the way off) the faucet. That will mainly involve phasing out the burning of fossil fuels by building a clean energy economy. Second, we need to drain water from the bathtub. That’s where carbon removal and sequestration in natural and technological “sinks” comes in. Trees and forests are a key example of natural carbon removal and sequestration:
It’s also critical to understand that many climate advocates are wary that carbon sequestration efforts will distract from measures to reduce emissions, or that carbon polluters will use them as an excuse to continue burning fossil fuels. The latest Intergovernmental Panel on Climate Change (IPCC) report was very clear that carbon removal and sequestration measures “cannot compensate for delayed emissions reductions.” Meeting the Paris targets will require both maximal emissions reductions and maximal carbon removal and sequestration efforts.
How much carbon sequestration is needed?
Removing at least 10 billion tons (gigatons, or Gt) of carbon dioxide from the atmosphere per year by 2050 is a reasonable ballpark target, as discussed below.
The IPCC report noted that carbon removal and sequestration can serve three purposes over different timescales:
- In the short-term, it can reduce net human greenhouse gas emissions.
- In the medium term, the IPCC noted that “the deployment of carbon dioxide removal to counterbalance hard-to-abate residual emissions is unavoidable if net zero CO2 or GHG emissions are to be achieved.” These hard-to-eliminate emissions include certain industrial activities, agricultural practices, and long-distance transport.
- In the long term, it can draw down the amount of carbon in the atmosphere to gradually reduce global temperatures to safer levels.
In a 2019 report, the National Academy of Sciences estimated that more than 10 Gt of greenhouse gases come from sources that will probably be very difficult or expensive to eliminate. So, since meeting the Paris targets of limiting global warming to less than 2°C above pre-industrial temperatures and ideally close to 1.5°C will require reaching net zero emissions somewhere between 2040 and 2080, 10 Gt of carbon dioxide removal and sequestration per year by 2050 is a reasonable global target.
Nationally, a 2022 study in Science suggested that to meet its 2030 Paris commitment, the U.S. would need to boost its annual natural carbon dioxide removal and sequestration from about 790 million tons (Mt) today to between 860 Mt and 1.16 Gt over the next 8 years (a 7–50% increase). The analysis found that most of that increase would likely come from trees, whose growth currently accounts for 95% of U.S. annual carbon removal and sequestration.
How much carbon sequestration can trees and forests provide?
Research suggests that just natural systems alone could deliver the carbon removal and sequestration we need by 2050, if we could fully maximize their potential.
Earth’s plants and soils collectively store more than three times as much carbon as currently resides in the atmosphere, so boosting that natural carbon storage offers significant potential toward curbing climate change. Several studies, including the aforementioned National Academy of Sciences report, agree that at a relatively modest cost of under $100 per ton of carbon dioxide, natural systems could remove over 10 Gt per year globally by 2050, including about 1 Gt from the U.S., much of which would come from forests.
In the United States, nearly one-third of the nation’s land area today is covered by forests, comprising about 1.4 trillion trees. They currently offset about 12% of American annual greenhouse gas emissions. The National Academy of Science report and several other studies suggest that fully replenishing all forestland that’s been depleted by factors like harvesting and wildfires, plus improving forest management practices could increase American forest carbon dioxide removal and sequestration by about 200–500 Mt per year (20–50% of the 1 Gt increase the National Academy of Sciences suggests the U.S. could achieve). This would offset a total of 15–20% of current annual national emissions, up from the current 12%.
About half of U.S. forest land is privately owned and harvested for products like wood and paper. Three-quarters of American forests' carbon removal and sequestration comes from these “private working” forests. While large old-growth trees commonly found in publicly-owned non-working forests are an important carbon storage system, it’s younger trees whose growth draws more carbon dioxide from the atmosphere every year. It’s thus important to both conserve old growth forests and the carbon they store, and to sustainably harvest and plant new trees that can pull additional carbon dioxide out of the atmosphere, especially if those harvested trees are used for durable wood products that can also continue to store carbon.
Are nature-based solutions big enough to merit CCL advocacy?
Yes. A recent study found that, to meet America’s 2030 Paris commitment, nature-based solutions (especially forests) will need to play a key role, accounting for about 8% of the greenhouse gas reductions needed over the remainder of this decade.
CCL has advocated for the single most efficient and cost-effective policy to reduce greenhouse gas emissions: an economy-wide carbon fee and dividend that directly tackles the pollution causing the problem. Nature-based solutions alone can’t match the huge potential to reduce greenhouse gas emissions that a robust carbon price can. But that’s true of all other potential climate solutions – there is no policy of similar size to a carbon price that targets greenhouse gas pollution in every sector of the economy.
Forestry policies specifically have only about one-tenth the potential effect of a carbon price. For example, maximizing afforestation (expanding forests) in the En-ROADS global climate policy simulator only reduces global temperatures by around 0.1°C compared to a business-as-usual scenario, while an aggressive carbon price can curb global warming by as much as 1°C.
But few individual solutions impact global temperatures by more than one or two tenths of a degree in the En-ROADS simulator. That’s why Project Drawdown’s list includes 100 solutions and a famous 2004 paper by two Princeton scientists identified 15 emissions ‘stabilization wedges.’ As Bill McKibben wrote of the climate problem way back in 2006, “There are no silver bullets, only silver buckshot.”
One might say, however, that carbon pricing is more like a silver shotgun – many of the solutions listed in Project Drawdown would be facilitated or incentivized by it. But it still can’t do everything. Natural carbon sequestration in plants and soils are particularly difficult to capture under the umbrella of a carbon price for reasons of measurement and verification in addition to ensuring permanence, as discussed below.
Of the available additional policy objectives, staff sought to identify those that could have a significant impact on greenhouse gases, have bipartisan appeal, would complement a carbon fee and dividend policy, and could benefit from CCL advocacy efforts, among other criteria. Nature-based solutions starting with forests fit the bill. And putting a price on fossil fuel carbon would not affect nature-based solutions, making them a smart complementary policy to add to CCL’s advocacy quiver.
Proportion of emissions cuts needed in each sector by 2030 to meet U.S. Nationally Determined Contribution (NDC), according to the average of model scenarios. Created by Dana Nuccitelli based on data from Bistline et al. (2022), Science.
In short, while forestry and other nature-based solutions may not match the scale of an economy-wide carbon price, they have similar potential for emissions reductions as other possible policies, are a good match for CCL’s advocacy strategy, and are a key solution needed to meet America’s 2030 Paris commitment.
What about wildfires and other climate impacts on forests?
Forests are vulnerable to a variety of climate change impacts including wildfires, expanding bark beetle populations, droughts, and heatwaves. When trees burn or decay as a result of these climate-worsened impacts, their stored carbon is released back into the atmosphere.
For example, an analysis by Carbon Plan suggested that, due to its recent large wildfire seasons, California’s forests may have released more carbon than they removed from the atmosphere over the past several years and will likely continue to do so in the future. As a result, carbon storage permanence is a challenge for forestry solutions. It’s thus important for forestry policy to take climate change into account, as discussed in the section below.
Fortunately, the southern states include the largest proportion of forested area in the country, with about half of their land area covered by forests, and this region has not been subject to the record droughts, wildfires, and bark beetle outbreaks plaguing the western states.
Percent of land in each county that is forested, according to the US Forest Service.
Co-benefits and the importance of tree equity
Trees provide many valuable benefits, in addition to helping to curb climate change. For example, conserving and restoring depleted forests can help protect biodiversity in those ecosystems, and climate-smart forestry practices can help lessen the severity of wildfires.
Trees also provide physical and mental health benefits. Research has shown that spending time around trees reduces stress, lowers blood pressure and improves mood. Trees also improve air quality and provide cooling, which are particularly important services in urban areas whose residents face significant physical health risks due to a high density of local pollution sources and heat emanating from surfaces like asphalt and concrete. One recent study found that in 35 U.S. metropolitan areas, about 36,000 premature deaths could have been avoided over the past 20 years by planting more trees.
According to a Tree Equity Score analysis done by American Forests, communities of color have 33% less tree canopy on average than majority white neighborhoods, and poor communities have 41% less tree canopy than wealthy neighborhoods. Smart urban tree planting can thus both contribute to slowing climate change and begin to reverse this source of environmental injustice while improving those neighborhoods’ resilience and ability to adapt to certain climate change impacts like extreme heat.
Bipartisan support and local engagement
There have been numerous bills related to forests that have been introduced in Congress and include both Republican and Democratic cosponsors. Among these is the FOREST Act, which would restrict goods originating from illegally deforested land. It has bipartisan support in both chambers of Congress and has been included among CCL’s supporting asks.
It’s important to ensure that forestry legislation does not encourage activities such as clearcutting forests or monoculture tree planting that do more harm than good. CCL will not support counterproductive forestry legislation. A 2010 study showed that higher temperatures and CO2 levels can actually increase carbon sequestration in forests, but only if adverse climate effects like fires and drought don’t wipe out any potential gains.
Volunteers can also engage with solutions like tree planting at the local level. For example, the Girl Scout Tree Promise aims to plant five million trees in five years. Local tree projects offer the opportunity for volunteers to engage in climate solutions in their own communities, while potentially helping to alleviate the problem of tree inequality in low-income neighborhoods and communities of color.
Intro & Agenda
Forestry Opportunities, Challenges
Tree Equity & Benefits
- Dana Nuccitelli
Intro & Agenda
Forestry Opportunities, Challenges
Tree Equity & Benefits
- Dana Nuccitelli
- American Forests website
- Reforestation Hub tool
- World Resources Institute CarbonShot federal policy options report
- Tree Equity Score analyzer
- Sustainable Forestry Initiative website
- National Academy of Sciences report on carbon dioxide removal
- IPCC Sixth Assessment Report, Mitigation Volume
- What you need to know about carbon dioxide removal
- Talk to your local tree and forest experts