 I'm going to go with actually is the role of nature-based solutions in negative emissions portfolios kind of like gets at some of the work we've been doing lately and the work we have some funding from CERC for, so. Just briefly, some of the key people involved, yeah, my name is Connor Nolan. I'm a postdoc with Chris. I've been here at Stanford for about three years. I got my Ph.D. at University of Arizona doing paleo climate, paleo ecology. Now I've been doing a lot of cool stuff here with Chris. You guys all know, don't really need an introduction, but. And then Katherine Mock is a, she was a research scientist with Chris for years and now as a professor at University of Miami doing lots of climate adaptation, decision making under deep uncertainty, a lot of cool stuff. And then some other postdocs and students. So Kyle Hems was a postdoc here with Chris and he and I worked on this grant proposal that we got funded from CERC. Anela Arifi is a current Ph.D. student with Chris. And then a couple of really great undergrads, Cecilia of Vampassion and Jevin U. So, yeah, I'm going to jump in. Much more kind of like big picture and conceptual than some of the awesome deeply informed, deeply modeled energy systems and other cool stuff we've been hearing about today. But talk about forests and negative emissions. So, negative emissions, we know we've been slow to decarbonize and in order to meet ambitious warming goals to limit warming to two degrees or 1.5 degrees, we pretty much surely need some amount of negative emissions. Negative emissions are intentional human efforts to remove CO2 from the atmosphere. And we're going to need them from a portfolio of different technologies. So, ranging from things like natural climate solutions like aphorization, reforestation and soil carbon sequestration to more technological like bioenergy, direct air capture, weathering, ocean fertilization and so on. Let's see, this portfolio, we were really inspired by this really good report by Livermore National Lab about getting to neutral and negative emissions in California that came out in 2020. And in this report, they found that California likely needs around 125 million tons of negative emissions to get to net zero but on the state's kind of climate timeline. And about 20% of that, 25 million tons can come from natural and working lands. Some 84 million tons can come from biomass energy with carbon capture and storage from waste biomass. And the balance comes from implementing direct air capture and with carbon capture and storage. So, we're interested in the, wait, what like these kind of portfolio approaches and what they look like. And we're interested in what they look like on the ground at the local scale and like scaled up to the earth system impact in terms of what are the kind of global feedbacks and accounting challenges and how do you make sure that you're actually removing CO2 and lowering the atmospheric CO2 in order to make progress on climate goals. Not just kind of creating a market that might not do anything. And then how do you like avoid burdens on local communities and how do you make sure you're doing good beyond carbon and having co-benefits and not having bad costs. So, we started with a bunch of like a couple of years ago with a grant from Climate and Leisure Alliance to do some scoping work about realistic potential from nature. So, there's all these different, you know, estimates out there in the literature, some really high numbers for the potential role of nature. But we wanted to kind of go through a little bit more systematically and that's, I'm going to talk a little about that paper which is out in Nature Reviews, Earth and Environment. And then we also let a report for a science assessment report about forests and climate for the Climate and Land Use Alliance that kind of gets at this kind of how forests are simultaneously impacted by climate change and part of climate change mitigation and adaptation. And so, that's here. So, forests are at risk from climate change because heat and drought stress from fires and other insects and other disturbances, they're a part of the problem from climate change in terms of deforestation and forest degradation contributing major carbon emissions in the atmosphere. But they can also be a part of the solution to climate change contributing significant mitigation and adaptation benefits. So, some of those climate change mitigation benefits come from these kind of categories of protect, manage and restore, avoiding deforestation, can have significant positive impact on the climate and it can really maintain biodiversity and another important role of intact forests. Changing forest management, like by reducing harvest times and lengthening rotations can have a lot of potential globally on the scale of a billion tons a year. We see a lot of these kinds of projects in the California compliance market. And then reforestation, deforestation is maybe a very large technical potential, a much smaller cost effective potential and it can really have contribute negative emissions. So, talking through some of these more often, aren't any new ideas like when going through some of this work we found, you know, papers going back to early 90s saying tropical forestry response options to global climate change. And so, this has been in the literature for a long time. It hasn't been implemented at any large scale. It's still on the order of a million tons a year or something like that right now. But there's a lot of recent interest and trillion trees and other big kind of funding and press interest in the role of nature to solve climate change. And so, we want to come up and think about a realistic role for nature that kind of recognizes the full range of constraints. And so, we gathered a bunch of different estimates that we could find from the literature. We did a big meta-analysis where we gathered 42 natural climate solutions estimates from the literature. Things like papers we've seen like vasten at all the global tree restoration potential with that really big maximal estimates and other things about soil carbon and kind of summary papers and some of these old reports and new reports. So, we kind of searched far and wide for what we could find. And we converted them all to carbon gain potential over the 21st century. We found the total CO2 sequestration from these papers kind of estimates range from well over 1,000 billion tons of CO2 removed by natural climate solutions to, you know, under 100 depending on the kind of regions and the types of activities considered. But this orange shading in the middle is the IPCC AR5 estimates for negative emissions needed to limit warming to 1.5 degrees C and really only the maximal estimates for natural climate solutions potential anywhere near that. And we think a lot of those maximal estimates aren't possible because of a lot of these constraints. Like there's near term constraints around financing and governance and then there's longer term constraints about what's actually biogeochemically possible in terms of sequestering additional CO2 and ecosystems and then maintaining other ecosystem services, maintaining social political support, local indigenous access, all these things. So, we think near term governance and financing constraints are a big limiter and in the longer term biogeochemical constraints kind of set the long term potential. And so, doing a lot of these analysis looking at what papers consider what kinds of constraints, looking at a lot of the detail that you can all find in the paper, we come to this estimate that natural climate solutions can contribute something like 100 to 200 billion tons of CO2 removal over the next century. So, it's a significant amount and it's way bigger than any implementation that's out there right now. It's become a gigantic industry of natural climate solutions but it's nowhere near kind of like solving the climate crisis on its own. So, we need like a portfolio approach of negative emissions. And another big piece of this is that the kind of ability for net nature to contribute climate change mitigation is contingent on the overall climate trajectory that we're on. So, under high emissions scenarios, where we fail to limit warming, I mean getting this kind of three to four degrees C world, there's severe impacts on climate on forests and the opportunities become much more limited versus in a Paris consistent path, there's, you know, still significant to moderate impacts on forests but there's really big potential for forests to contribute. So, there's this kind of like contingency on overall climate actually because forests are like a solution that's at risk to the problem that they're trying to solve. And just showing this another way like so in a continued high emission scenario, you could actually have a situation where ambitious forestry interventions actually end up failing and worsening climate change impacts and, you know, maybe more moderate modest interventions can have limited and like limited positive benefits in any scenario. One interesting paper that came out recently showed that even if all nature based solutions are temporary, in this case they like implement like a hundred gigatons of reforestation and then they say it all reverses after 50 years. If you're on a SSP1 kind of scenario where you limit warming, even if all of the nature based solutions are temporary, they still significantly decrease the peak warming and can have a real effect. But obviously the decrease long-term warming is only like, only happens if the storage is permanent. So, there's benefits to doing nature based solutions even if you're not sure they're going to be permanent on thousand year timescales. So, yeah, that's kind of the summary of some of the stuff we were working on before. And now I'm going to jump into a few other pieces that kind of expand out to those other kind of our system impacts and portfolio approaches. And so, at the air system impacts one thing that's important to consider with nature based solutions is they have to be distinct from the already existing background sync. So, the background sync comprises natural and indirect effects, so natural effects like the CO2 uptake by photosynthesis and emissions from respiration and disturbance that kind of in equilibrium balances out to zero. And then with carbon with CO2 fertilization, nitrogen phosphorus fertilization, growing season length increases, we see this indirect background sync that does a lot of climate change mitigation in the background for us alone but isn't a natural climate solution in the way of negative emissions. And then there's direct management interventions like decreasing harvest rates or reforestation that can actually result in increases in carbon storage uptake. So, like this, these big bars that kind of balance each other out right now have this sync, are the environmental change background sync. This middle bar is the management and deforestation sync. And we really want to avoid natural climate solutions just being moving things from this small bar to like, or this environmental change and background bar to this managed bar and saying we did something when in reality that actually isn't doing anything and from the atmospheric perspective. We don't want to do that. So, this is a big problem for natural climate solutions. It's also a problem for things like enhanced weathering potentially and other kind of things that are taking advantage of ongoing earth system processes that create carbon sinks. So, one way that people have talked about doing this is adjusting the, adjusting integrated assessment models to match naturally determined contributions. So, integrated assessment models have this very clear distinction between managed and unmanaged land. These managed lands are the direct impacts that we want to capture in terms of natural climate solutions. Whereas nationally determined contributions have a significant land sink component that is on managed lands, but that's using a accounting quirk called the managed land proxy where you don't actually have to do anything. A country can just declare land to be managed and then the fluxes on that land become part of their progress towards their nationally determined contributions. So, this is not like, this kind of works and you can do this, you can do a Rosetta Stone approach for translating between these in the nationally determined contribution context, but it really doesn't work in a carbon market kind of context. You can't go back and easily adjust like the contribution of the land sink and the things. So, there needs to be a way to actually ensure that carbon market projects aren't taking credit for the background sink in a way that they shouldn't be. So, let's see. So, like, yeah, the background sink, it's super important. We want to maintain it, but we, it's not what we're talking about when we're talking about negative emissions from land. So, we have to really carefully distinguish between indirect and natural effects and then direct effects, the managed, that we really want to care about. One thing that would help to align these things is if countries would start reporting their nationally determined contributions with and without the contributions of the land sector. And, like, additional carbon uptake relative to the existing background sink has to be proven for carbon market forestry projects. So, one thing that is, you know, we are always keeping an eye on is that avoided deforestation projects can't take credit for something like a foregone sink or a foregone foregone sink if you get into the double negatives of it. So, yeah, that's some, the earth system accounting that's kind of in the weeds, but it's important to make sure as these things scale up. One thing that we're also working on in terms of negative emissions portfolios is these corporate climate plans as a big kind of proving ground for climate action and what these negative emissions portfolios can look like. So, Microsoft is a big leader in this space. They have a carbon negative by 2030 goal and remove all historical carbon emissions by 2050. They've, last year they purchased a million tons of CO2 removal and wrote a nice comment in nature about their lessons from that. And we're working with the Microsoft sustainability team to think about the role of nature in their portfolios. A kind of different approach is the Stripe Climate or the recently announced Frontier Climate, a partnership of Stripe and Alphabet Meta Shopify where these companies are just committing a big chunk of money, not necessarily trying to be carbon negative or net zero or anything like these, but they're committing a chunk of money towards expensive carbon removal. And so these, the two different approaches for corporate climate actions lead to different approaches on nature. So the Microsoft approach success is based on tons of CO2 removal versus the climate company approach. These are based on just levels of investment. The Microsoft approach because it requires them to get to a certain number of tons to meet their net zero goals, they have to have more widely available now and cheaper carbon dioxide removal versus these Frontier Climate approach. They are willing to spend any amount of money and they're spending in the kind of hundreds of dollars a ton range in some cases. And then, so the Microsoft approach just leads to a large role for nature-based carbon dioxide removal in their portfolio versus the Stripe and others approaches almost completely excludes nature because they're interested in these truly, for sure, permanent solutions. So it leads to a really challenging question of how do you compare nature-based carbon removal that's on this cheaper and widely available to these really expensive direct air capture and other things that are more permanent? So just to walk through some of the things that are in the market right now, you have these low quality carbon forest offsets that everyone agrees are not good. But these have comprised a large part of the voluntary carbon market as it currently exists. They're very cheap. They have a very low likelihood of limiting CO2 in the atmosphere and they have moderate to minimal co-benefits because they maybe are contributing to some amount of protection of land but they're not doing that much. On the other hand, some technological CO2 like bio-oil injection or biochar you have direct air capture. These are much more expensive, over $100 a ton in many cases. They're very likely to limit atmospheric, they're very likely to result in lowering atmospheric CO2. And their co-benefits, I don't know, questionable. We'll talk a little bit about that, not that much. That's not a focus of them. The focus is doing what, of lowering atmospheric CO2 and they're pretty good at doing that, it seems. And then, so what we wanna think about is what is a next generation nature for climate offset that might be more comparable in terms of price and have big co-benefits, have a good likelihood of lowering atmospheric CO2. And then we can start to say like this is actually comparable and we can start to make value judgments about what direction you wanna push your investment into. So nature-based, nature for climate next generation looks like nature-based climate solutions need to under-promise and over-deliver. This is a big change from how nature-based solutions are being sold right now. Nature can do a lot, but we don't have to oversell it. It doesn't have to provide billions of tons of additional CO2. It doesn't have to solve everything with all the co-benefits you can imagine and be at low cost. It can be, we want to under-promise and over-deliver. So one solution that we're thinking about is this kind of like over-buying approach where you, right now there's in the markets there's like a buffer pool that are 10 to 20% of the credits are saved out for reversals. We're thinking, what happens if you flip that? What if 50% or 80% of the credits are in the buffer pool and you only get credit for a small amount of the work that projects, the carbon that projects are measuring to do but you're much more light, much more confident that you're getting what you're paying for. You're getting some real carbon removal from nature. It's gonna make nature-based carbon dioxide removal more expensive, but it's also makes it more likely to deliver real benefits. And then the other piece is, how do you value the co-benefits that come with this? There's many reasons to invest in force beyond their carbon capacity. We want to not make carbon the main metric, but these have largely been external to carbon markets. It may be possible to try to internalize some of these co-benefits or take a different approach, like saying we do these really strong carbon focus and then we say you've graded on some co-benefits around your biodiversity protection and your sustainable development contributions and other issues that goes on top of the like more rock solid carbon numbers that you're getting by our over buying kind of reverse buffer pool approach. So this is really important because nature's high leverage. That this is kind of my starting to wrap up here. It's an investment in nature, has a potential for these big win-wins across climate and conservation and sustainable development. But if it's done poorly, there are risk of big lose-lose outcomes across all these things we care about in terms of climate, conservation, sustainable development. So we want to make sure to get nature right. And right now there's a big risk in the market of getting nature wrong. So some of our future work is to keep going on all these and start to think about what are these portfolios really look like on the ground? We're working with, like I said, some of these corporate partners and they have real money that they're spending and they're doing to try to implement these projects and figure out the standards that work for across the buyers and the providers of assets across the verifiers and all these things. And then I think one thing that like we've been thinking about is like extending some of these concepts you see in nature-based solutions and talks about what are the co-benefits of direct air capture and other of these things? Like there's how do you value things like jobs and rural economies and just transition for fossil fuel workers and things like that? How do you weigh something like that which has real value against something like the biodiversity protection? It's not necessarily straightforward but there's real opportunities to kind of lay out the options and make decisions based on data and based on like what we actually want to do to get climate right. So just wrap up with this. Negative emissions are necessary, are likely to be necessary. We want to make sure there's quality and there's a real constituency for quality that's emerged. Nature's got a role to play but it's only one piece of the puzzle and carbon essential but it's not everything. So thanks everybody for listening. Happy to be able to be here and talk about some of our work. There's my email down at the bottom. Thanks Conor. We have a couple of minutes if anyone wants to ask any questions. Hi, yeah, thanks. Thank you Conor, that was great. I just want to make sure I understand something and also a question. So it seems very complicated the direct and indirect, you know, like those categories. And I noticed in the indirect you had extended growing season and all that. I'm just wondering where like modified crops or that would potentially fit into this assessment. And correct me, are you just looking at trees like reforestation? Are you looking at other crops or plants? Is there a way to have these natural climate solutions and carbon benefits? We are literature research was looking at mainly it was a lot of mostly forest and some soil carbon sequestrations like summaries. We didn't look a lot about like the individual like some of the kind of technological plant type stuff that's really cool. And I think has the benefits. I think those things would be very clearly in the kind of direct managed aspect of this because they're, you know, doing a implementing a project that with a specific goal of carbon in mind. So, and that you could, you know, see how they're doing compared to standard plants and make a clear assessment of what the additional carbon storage was from that. And that would be like, you know, very much worthy of carbon crediting under standard. Yeah. And is there much of that going on anywhere in the world right now? I don't think so. I think like with a lot of things we see like there's a lot of talk about natural climate solutions and things but there's very little on the ground when you try to dig into these things happening right now. So with the teaser of your next work how would you compare biodiversity benefits versus job benefits? Do you have initial thoughts on that? That sounds tricky. Yeah, it sounds, it's definitely tricky. I mean, I think it's gonna, I don't know that there's like a quantitative, there's probably, there's so many like, you know, like choices and ethic, like just, you know, involved about, so to make it quantitative. But I think one thing we're thinking about is that projects should have some co-benefits and like they should be doing good beyond carbon. And so like that might look like some kind of standards body that evaluates the co-benefits, the suite of co-benefits for a project. And that could be biodiversity or it could be water or it could be jobs and just transition. So like, I think there's gonna be a lot of like qualitative judgments involved. And but it's just, we wanna make sure that project developers are thinking about these things and thinking about how they're doing good beyond carbon.