Counting Carbon in US Forests, with David Wear

Notable Quotes

• US forests help offset carbon dioxide emissions: “If we look at the standing inventory of carbon in forests today, it’s about 52 times the annual emissions from the US economy. Now, if we look at how that reservoir of carbon is changing over time, it’s evolving at about … half a percent per year … The growth in that reservoir is the amount of carbon that forests are extracting from the atmosphere every year … That amounts to about 13 percent of US emissions of greenhouse gases in any given year.” (3:08)
• Federal government may be overestimating how much carbon US lands can sequester: “Right now, our projections indicate that we would have less carbon benefits from the land sector than, say, our US strategy for net zero anticipates. If we have less carbon dioxide removals, then we need to accomplish more emission reductions in other parts of the economy.” (13:47)
• Protecting existing forests is an effective strategy: “It’s clear that the benefits of avoiding deforestation are greater than the benefits of new afforestation over the next 40 years in every ecoregion in the United States … Effective policy addressing land-sector carbon should be focused on avoiding deforestation, minimizing the land use footprint of additional development, as well as incentivizing afforestation or building out those kinds of nature-based climate solutions moving forward.” (19:29)

Top of the Stack

• “Land Use Change, No-Net-Loss Policies, and Effects on Carbon Dioxide Removals” by David N. Wear and Matthew Wibbenmeyer
• “Managing Wildfires to Combat Climate Change” episode of Resources Radio with David Wear
• A Sand County Almanac by Aldo Leopold
• The American West as Living Space by Wallace Stegner
• “The Great Cash-for-Carbon Hustle” by Heidi Blake

The Full Transcript

Daniel Raimi: Hello, and welcome to Resources Radio, a weekly podcast from Resources for the Future (RFF). I'm your host, Daniel Raimi. Today, we talk with Dave Wear, a nonresident senior fellow and director of the Land Use, Forestry, and Agriculture Program here at RFF.

Along with our colleague Matt Wibbenmeyer, Dave has recently published some new analysis that seeks to improve the way that we account for carbon dioxide (CO2) removals from the forest sector in the United States. This might sound a little wonky, and it is, but it's also extremely important. That's because forests are the dominant tool we currently have to remove CO2 from the atmosphere, and reaching net-zero emissions targets will almost certainly include them—but how do we measure the emissions that forests remove, and how do we make sure that projects designed to remove CO2 really do what they claim? That's what we'll talk about in today's episode. Stay with us.

Dave Wear, my colleague at Resources for the Future, welcome back to Resources Radio.

Dave Wear: Thanks, Daniel. It's great to be here.

Daniel Raimi: Dave, we're going to talk today about some new work that you've recently published with our colleague Matthew Wibbenmeyer at RFF about forestry and land use changes and effects on carbon dioxide removals. It's going to be a really fascinating conversation.

We usually ask our guests to introduce themselves the first time they've been on the show, but you've been on the show before so we're not going to ask you to do that. We had you on—I think it was about a year and a half or two years ago—talking about wildfire management.

Dave Wear: That's right.

Daniel Raimi: Since that time, you've joined us at RFF on a full-time basis, so it's really great to be working with you more regularly.

Dave Wear: It's great to be doing this work.

Daniel Raimi: My favorite part about talking and working with you, Dave, is that you live in Durham, North Carolina, where I grew up. Every time we talk, I get to hear about the latest and greatest happenings in the Bull City.

Dave Wear: That's right.

Daniel Raimi: Let's dive into our subject matter, Dave. As I mentioned, our conversation is going to revolve around this paper that you and Matt wrote, and that's called “Land-Use Change, No-Net-Loss Policies, and Effects on Carbon Dioxide Removals.” If that doesn't make sense to the listeners, we're going to break it all down in the next 30 minutes or so, and, of course, we'll have a link in the show notes to the paper so people can dig into the details.

Let's start with two really basic questions. First, when we're talking about carbon dioxide removal, or CDR, what role do forests and other vegetation play in the United States, in terms of removing carbon dioxide from the atmosphere each year? Second, have there been changes to that rate of CDR over time, and why?

Dave Wear: I’ll start by pointing out that forests of the United States store a vast amount of carbon in solid biomass, and this carbon comes from basic photosynthesis, as forests absorb carbon dioxide from the atmosphere and use it to build biomass. If we look at the standing inventory of carbon in forests today, it's about 52 times the annual emissions from the US economy.

Now, if we look at how that reservoir of carbon is changing over time, it's evolving at about 0.5 percent per year, or half a percent per year. That's a description of how fast that reservoir is growing. The growth in that reservoir is the amount of carbon that forests are extracting from the atmosphere every year. Half a percent doesn't sound like a lot, but, across this vast inventory, that amounts to about 13 percent of US emissions of greenhouse gases in any given year. It is consequential, and, as we look to the future, carbon dioxide removals are a really important part of strategies to reach net-zero emissions, because clearly there are parts of the economy that are very difficult to decarbonize, and finding some way to pull carbon dioxide out of the atmosphere is really important.

Daniel Raimi: That's great. One technical clarifying question—when you talk about forests, are you talking about just the standing biomass, or are you also including carbon that might be stored in soils and other vegetation in and around forests?

Dave Wear: Following standard practice, we include the soil, as well as the above-ground and below-ground vegetation.

Daniel Raimi: Great. Let's talk now about the analysis that you and Matt carry out. In the paper, you focus on accounting protocols, which turn out to be really consequential, and you talk about two different kinds of accounting protocols for how to measure changes in the extent of US forests and the carbon stocks that they hold. Can you tell us about those two accounting approaches? And then we'll talk more about which one is preferable in a couple of minutes.

Dave Wear: Well, first I'll back up and talk a little bit more about carbon dioxide removals. I mentioned that the rate of change is about a half a percent per year. If we break that down a little bit, that's the net change. The net change comes as the result of gains that are accumulating due to photosynthesis and the accumulation of biomass in forest lands and losses that are also constantly occurring. Those can be emissions that are due to wildfire or to insect and disease outbreaks. There's also a set of carbon transfers from forest into wood products and also emissions from harvesting.

Then, another and really critical part of this is land use change. The amount of forest matters a lot. In any given year, we have forest area that's being converted to some kind of developed use, or we have agricultural land that's being planted or otherwise regenerating to forest. As we've looked at dynamics—understand that land use change is a really critical driver in determining what carbon dioxide removals occur in the land sector and, specifically, in forests in any given year.

That said, how we account for land use change can have a big effect on our estimates of carbon dioxide removals. Especially as we are trying to project what carbon dioxide removals will be in the future, we need to account for how land use change is likely to affect our forest.If we think about it, one way to do it is just to track the amount of forest from year to year, which is basically looking at net change. If we have an accounting approach that just takes the area of forest over time and looks at net change, we have one accounting approach. The other accounting approach, which is more detailed, is to account for where and how forest is lost to other uses and where and how forest is gained—both across space and time.

This is important, because we have a lot of discussion of land use policy that goes to net-loss objectives or it goes to specific afforestation and deforestation objectives. We found, in doing our analysis, that there are some really important and consequential differences in the results you get when you use those two different accounting rules.

Daniel Raimi: Take us a level deeper on that. What are some of the implications of using those two different approaches? You make the case with Matt that one is sort of clearly preferable over the other.

Dave Wear: In some ways, this isn't surprising. If you use a net-loss approach in an area where you're seeing a lot of gains and losses offsetting one another, you can overestimate the amount of carbon dioxide removals you're likely to get from that landscape. So, regardless of where we apply this model across all the regions of the United States, using a no-net-loss approach—or a net-loss approach, I should say—leads to a positive bias. That's a clear indication that you want to avoid using that kind of accounting to look at carbon dioxide rules.

Daniel Raimi: Can you maybe give us an example to help us kind of intuit that? Maybe like an example forest where part of it is being changed and put into some kind of developed use, whereas biomass is growing in some other part of the forest? Can you just talk us through—not the math, necessarily—but the intuition for why this makes sense?

Dave Wear: The intuition is this: There is a reservoir of carbon in a given forest area. When that forest area is bulldozed for development, that carbon is lost to the atmosphere. So, the emissions of carbon from that loss are much greater than the gains in carbon, at least in the early years, from a newly planted forest area.

That's the underpinning of all of this: You need to account for how each of those mechanisms generate some kind of net emission, whether that be a negative emission, which is sequestration of carbon, or positive emission, which is an exchange that leads to carbon dioxide in the atmosphere.

Daniel Raimi: Right. So, in that example, the area that's bulldozed is replaced by some new planting elsewhere, so that's a no net loss in forest land, but there are still emissions, because the carbon that you lost from the bulldozed area is greater than the carbon that you've sequestered in the newly planted area. Is that right?

Dave Wear: Exactly. Yes.

Daniel Raimi: Great.

You and Matt also examine some of the carbon dioxide removal implications looking toward the future using these different types of accounting approaches. Can you talk about some of those projections and what they tell us about how CDR might play a role in the decades ahead in the US forest sector?

Dave Wear: I should probably point out that this is the second paper that Matt and I have written on this topic of carbon dioxide removals from the land sector. In the previous paper, we spend a lot of time looking at specific projections of carbon dioxide removals. Carbon dioxide removals in the forest sector are substantial and consequential, I would argue, but they've also been declining over time. Over the last 30 years, the rate of removal has declined by about 10 percent. If we take a business-as-usual future, over the next 40 years, we would expect the rate of carbon dioxide removal to decline another 20 percent.

That's largely because forests in the United States are getting older. We've had a fairly young age class distribution of forests, especially in the eastern United States where most of the carbon sequestration occurs. As those forests have aged to a certain point, the rate of carbon dioxide removals has been declining. So we expect that to continue moving forward.

If we begin to play out the differences between these accounting approaches, the rate of carbon dioxide removals that would be estimated if we used a net-loss accounting approach would be 50 percent higher than what we see by accounting for both afforestation and deforestation.

Daniel Raimi: There are clear implications here for policy and also for international accounting to bodies like the United Nations Framework Convention on Climate Change and the Paris Agreement, is that right?

Dave Wear: That's true. I should point out that the United States does a good job of accounting for the detailed dynamics of historical change. I think it's especially important for how we build out our expectations for net emissions moving forward. CDR, or carbon dioxide removals, are expected to play an important role and we need some realistic expectations about what the land sector can continue to provide.

Right now, our projections indicate that we would have less carbon benefits from the land sector than, say, our US strategy for net zero anticipates. If we have less carbon dioxide removals, then we need to accomplish more emission reductions in other parts of the economy.

Daniel Raimi: That's so interesting. It makes me wonder how much you're engaged with policymakers. On this question, are you talking to the folks at the US Environmental Protection Agency or the US Department of Agriculture or wherever else these accounting protocols are actually being implemented?

Dave Wear: We're in the process of building out our models, and, as we go, we've been involved with a community of modelers and policymakers who need to understand these outcomes.

Daniel Raimi: Yeah, great. Once again, RFF research—it's detailed, and it's high quality, and it's academic work, but it's also informing the real world, so that's great.

Dave, one thing that you and Matt talk about in the paper is regional variation. I think it'll be intuitive to people that there are different types of forests across the United States with different ages and species, and they're affected by factors that vary regionally. Can you talk a little bit about that regional variation and how it plays into this question of carbon dioxide removals?

Dave Wear: Sure. If we look at the forests of the United States, there are some really important differences on either side of the 100th meridian and, at finer grain, across the landscape.

Daniel Raimi: Dave, I'm sorry to interrupt, but for the geographically challenged among us, including myself, what's the 100th meridian?

Dave Wear: Well, let's just say east and west of the Great Plains.

Daniel Raimi: Got it.

Dave Wear: If we look at the eastern United States, we've benefited from a century of reforestation in this region. Forests are relatively young, and this is where the lion's share—about 80 percent—of forest carbon sequestration occurs in the eastern United States. We expect that that share is going to increase to at least 90 percent in the coming decades.

If we look to the west, we see fairly old forests that are being impacted by wildfires in many places. We've seen forests in the western part of the United States actually move from being a small sink or producing net carbon dioxide removals to being a source of carbon emissions, as those forests adjust through wildfire and land use change. There's some really important regional differences that we need to pay attention to in terms of building out policy.

Daniel Raimi: That's so interesting, and it makes me think of another question that is almost certainly an entire podcast unto itself, which is, when we think about projecting future CDR in these western forests that are exposed to wildfire risk, how much confidence do we have in our ability to make those projections, given—from my lay perspective—the rapid increase in extreme wildfires in the western United States and parts of Canada?

Dave Wear: That introduces a certain amount of uncertainty, for sure. I would say that, in most cases, the wildfire crisis is driven by overstocked stands—in other words, fire suppression has largely eliminated fire from its natural role in forests, so you have more carbon dioxide than can perhaps be sustained. One way to look at this period might be that we're in the process of adjusting those carbon reservoirs in western forests to a more appropriate level, and that's going to involve some net emissions.

Now, the big question is, how will climate change interact with those forests in determining what the ultimate sustainable level of carbon storage would be? I think a really important part of looking at our wildfire strategies is trying to manage or maybe mitigate the emissions signature of our fuel treatments and of our difficult challenges of negotiating this change.

Daniel Raimi: For listeners who are interested in learning a little bit more about our approaches to managing wildfire, I would point folks to the previous conversation that we had, Dave, a year and a half or two years ago. We'll have a link to that in the show notes, too.

One more policy question. We've already talked about a couple policy issues. It seems clear from this work that using a net change approach in accounting is not the right way to go. Can you talk about some other policy implications that you and Matt draw from this work?

Dave Wear: Well, if you look under the hood of this big modeling effort to try to get at accurate projections of change in carbon dioxide removals, it's clear that the benefits of avoiding deforestation are greater than the benefits of new afforestation over the next 40 years in every ecoregion in the United States. Now, what that says is that effective policy addressing land-sector carbon should be focused on avoiding deforestation, minimizing the land use footprint of additional development, as well as incentivizing afforestation or building out those kinds of nature-based climate solutions moving forward.

Daniel Raimi: Is that just because, when we're planting new trees, those trees are just physically so small that they're not sequestering a large amount of carbon until they're maybe 40 or 50 years older, or are there other dynamics going on there?

Dave Wear: That's essentially the idea that's driving this. At least in the immediate- or medium-run future, it takes a while to recapture any kind of forest loss from development in a new forest. So, given the time frame of our climate commitments and the rapidity of climate change, it's an important consideration.

Daniel Raimi: Right. I've managed to very slowly get to the very simple point that trees grow slowly.

Dave, one other question that I can't resist asking you—and this is a little bit off topic, but it sort of connects—is about the role of forestry offsets, which listeners have certainly heard about. I feel like there's always new stories about forest carbon offsets and problematic examples of them, but there was a new round of them maybe a month ago or so. There was a story in the New Yorker that I read that is all about a company that was developing a very large carbon offset project in East Africa. The reporting was pretty compelling, including getting quotes from some of the project developers that a lot of the carbon offsets that companies were purchasing on the back of this forest project were mostly hot air. That is, these carbon offsets were really not actually offsetting much carbon at all. The name of the article was, “The Great Cash-for-Carbon Hustle,” which gives you a flavor for the tone of the piece.

I'm just curious if you can talk about this issue a little bit? How concerned are you about these potentially “hot air”–type projects? Then, how concerned are you that the reputation of forests as a useful tool in our carbon toolbox are getting this really potentially bad reputation?

Dave Wear: Well, I will start with just the general observation that we know that we need carbon dioxide removals to get to net zero. As I mentioned earlier, there're just parts of the economy that are very difficult to decarbonize. We're anticipating that technology will begin to deliver some scalable approaches to carbon capture and storage and effective CDR. But, in the meantime, forests in the land sector are the only mechanism for withdrawing or capturing carbon from the atmosphere and generating CDR. We know, through this modeling effort and others, that it is possible to grow that sink from some kind of baseline level—that it can be grown in a consequential way and generate some benefits for society.

We face this conundrum of, well, how do you incentivize that? What mechanisms do you use? Do you use some kind of command to control? Some policy approach at the federal level that actually generates that benefit through additional afforestation, whether that be through subsidized tree planning or some other tax incentive or subsidy? Or do you use the private sector to generate these benefits?

That article in the New Yorker is a case study of some fairly egregious behavior by some early efforts to capitalize on the demand for carbon offsets. I think there are lessons to be learned from it. At the same time, I know that there's an awful lot of really good work going on, especially in the forest sector, about how to generate verifiable, transparent, and useful credits. That is encouraging to me. We've come through perhaps the “Wild West” period of carbon offsets, and now we're moving toward something with some really hard-nosed science and hard-nosed accounting behind it.

Daniel Raimi: Right, and that's exactly the work that you and Matt and many others are doing so that we can have verifiable CDR in the forest sector. That's really important.

I'm curious—just one last question about this reputational issue, Dave, before we go to the Top of the Stack. When you talk with people outside of the research community who understand the ins and outs of accounting and maybe the progress that's been made in recent years, do you encounter a lot of skepticism with regard to CDR in the forest sector, and do you think that it might be difficult to rehabilitate the reputation of forest CDR projects?

Dave Wear: I hope not. As I talk to people, especially in the forest sector, it seems that we're moving toward good, verifiable, solid, transparent credits and offsets. You're getting at a really important element of the question, and that is, how do we maintain the social license to pursue this avenue for generating climate benefits?

Daniel Raimi: It's going to be really interesting to watch it play out in the years ahead, and, hopefully, the work that you and Matt and others are doing can maybe rehabilitate some of that reputational risk that comes when splotchy stories like this come in the New Yorker.

Well, Dave Wear from RFF, this has been a really fascinating conversation. It's technical, but it's so interesting and so important. I really appreciate you explaining it to us.

We'd love to close out the conversation now with the same question that we ask all of our guests, which is to recommend something that's at the top of your literal or metaphorical reading stack, that you've read or watched or heard. It could be any kind of media. It could be related to the environment or maybe just loosely related to the environment. We're pretty flexible around here. What's at the top of your stack, Dave?

Dave Wear: Well, I'm staring across the room at the stack, which is a little too tall right now, but I've lately been rereading some conservation essays from the past. Things like Aldo Leopold’s Sand County Almanac, but especially Wallace Stegner's writing about living in the western United States and the limits of climate and topography on living in the west and just stimulating some thought about the land ethic and how to contemplate the land ethic in an era of climate change. One thing that's especially interesting to me is, as I read Stegner, who is writing in the seventies and eighties about life in the West, it's focused on aridity and the limits of water or limits imposed by water, and it doesn't mention wildfire. I have to believe he'd be talking about wildfire if he was writing today.

Daniel Raimi: Yeah. Well, Dave, this has again been a really fascinating conversation. Thank you so much for coming out to the show and sharing your expertise with us. We really appreciate it.

Dave Wear: It's a pleasure. Thanks, Daniel.

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