The Climate Biotech Podcast

Unveiling the Role of Trees in Methane Removal with Vince Gauci

• Homeworld Collective • Season 1 • Episode 3

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How do upland trees contribute to the fight against climate change? Join us as we uncover the unexpected climate services of trees with Vince Gauci, an ecosystem scientist and biogeochemist at the University of Birmingham. 

In this episode of The Climate Biotech Podcast, we delve into the fascinating world of methane uptake by trees with ecosystem scientist and biogeochemist Vince Gauci. His groundbreaking research at the University of Birmingham offers new insights into the hidden roles that trees play in mitigating climate change. 

Throughout the episode, Vince's passion for ecosystem science and his dedication to addressing climate change are evident. His work underscores the importance of interdisciplinary approaches and integrating process-level research with large-scale modeling to provide a holistic understanding of ecosystem dynamics. This episode is packed with thought-provoking insights for researchers, policymakers, and environmental enthusiasts alike.


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Dan Goodwin:

Welcome to the Climate Biotech podcast, where we explore the most important problems at the intersection of climate and biology and, most importantly, how we can solve them. I'm Dan Goodwin, a technologist who spent years transitioning from software and neuroscience to a career in climate biotechnology. As your host, I will interview our sector's most creative voices, from scientists and entrepreneurs to policymakers and investors. We are thrilled to have Vince Gauci joining us from Birmingham, England. Vince is an ecosystem scientist and biogeochemist who leads a research group at the University of Birmingham in the School of Geography, Earth and Environmental Sciences. He specializes in atmospheric interactions with carbon-rich ecosystems such as forests, wetlands and peatlands. His work frequently covers methane-nitrous oxide cycles, which are both increasingly driving climate change.

Dan Goodwin:

Today, our conversation will focus on Vince's exciting new findings, published on July 23rd in Nature, that implicate methanotroph-colonized woody surfaces climate change. Today, our conversation will focus on Vince's exciting new findings, published in July 23rd in Nature, that implicate methanotroph colonized woody surfaces as a major contributor to terrestrial methane budget. We will explore the potential of leveraging these findings for atmospheric methane removal, the challenges to getting there and the remaining open questions. For preview, you can check out the perspective Vince published on July in environmental research letters for the role of trees in methane mitigation. So, Vince, thank you so much for joining us today. How are you doing?

Vince Gauci:

Thank you, dan, and thanks for that lovely introduction. I'm delighted to be here.

Dan Goodwin:

Great, it's wonderful to have you, vince, and so the question we ask everyone before we get into the science is who are you and where did you grow up?

Vince Gauci:

Okay, so as you can probably tell from my accent, I'm not from your shores. I grew up in suburban West London. I went through a kind of a range of different interests, but I was always fascinated by the natural world, from quite a young age and as I grew up. Unfortunately, one of the things with UK education is that we specialise very early, and I specialised at 16 in mathematics, physics and chemistry. That was it. That was all I did, and I didn't do them particularly well. It wasn't a great time for me to be engaging in something that I thought would be great and actually it didn't float my boat so much. I should really have been doing things like geography and biology, which would have been far more useful coming through. So with that, I ended up starting a degree in mathematical physics and it was just so abstract and it just didn't appeal to me. I remembered my interest in the natural world and I ended up switching. I had to switch university. I couldn't just switch course. I switched university to do environmental science and as a part of that I had the option to spend my third year of four normally they're three years, but you could take an extra year and I did that as an intern with the US Forest Service and with Oregon State University. So I ended up spending a year in the Cascade Mountains of Oregon. Hey, I was lucky. That was great. I had a lovely time and that's what really turned me on to this sort of subject and what I was doing.

Vince Gauci:

I was working for a professor who sadly a couple of years ago passed away, called Bob Griffiths, and he was fascinated by roots and mycorrhizal fungi and their respiratory functioning. So my job out there, this guy who's still an undergraduate he's only done two years of anything even remotely relevant. I was running his program out there. I was making measurements on the forest floor of CO2 exchange, soil respiration, so that sort of got me into ecosystem processes at the ecosystem level. And then after that I went on.

Vince Gauci:

I did a PhD with the Open University in tandem with the Centre for Ecology and Hydrology in Edinburgh. So I was mostly based in Edinburgh and I was working on peatlands there. I was mostly based in Edinburgh and I was working on peatlands there. I applied because I saw there was potential in this area which at the time, in the mid sort of 90s, it was already starting to become old hat, and that was the effects of acid rain pollution. So I essentially simulated sulfur deposition on peatlands with the idea that sulfur pollution and the sulfate that would go into the peat under anaerobic conditions would stimulate a competition between sulfate reducers and the methanogens, the things that are actually producing the methane. So that was fun and I was operating at that kind of ecosystem level again.

Vince Gauci:

But that's where my curiosity led me in a direction that sought to integrate over different scales. So I did some process level work. But then I got a visiting fellowship at NASA Goddard Institute of Space Studies in New York City and I don't know if you guys remember, or what was it called, seinfeld, okay, so you must all know Seinfeld, of course you do. So it's above Tom's Diner where they would regularly go that, that diner so I spent a summer there in a heat wave with no AC.

Vince Gauci:

It was really challenging in in many respects. I didn't know how to code but I was mixing with all these people who are working. Elaine Matthews was the main one who I was working with and she'd developed one of the early sort of wetland models wetland distribution maps and then I started working with a few other people. One of the consequences of having a general circulation model is that they have sulfur in the atmosphere because of aerosols but they have to drop out. So I was interested in that sulfur that was dropping out and how that would stimulate competition with the methanogens.

Vince Gauci:

It was very nice and that was my second paper for my PhD, which ended up in PNAS, and Jim Hansen was the editor of that. He's guided it through, and Jim Hansen was the editor of that and he's guided it through. So it was lovely at that early stage in the early 2000s to be producing that sort of work and it got some interest as well in the media etc. And yeah. So I think what that approach taught me was that it was quite important and interesting to not just examine at a process level and how it manifested at the ecosystem level, but also what that could potentially mean at large scales, at the global level, and that I've carried that through with a number of studies I've done, and certainly with this one. That's possibly why the nature paper took so long to publish.

Vince Gauci:

It was the challenges of upscale were of upscaling were not trivial. So, yeah, that's how I got into postdoc lectureships and became a chair in global change ecology at the Open University and then I moved about five years ago just immediately pre-COVID moved to university of birmingham with birmingham institute of forest research. Uh, which has been wonderful. Yeah, that's my background. That's not quite a nutshell, is it?

Dan Goodwin:

but I think it's quite comprehensive it is, and what I really like about your story is that you've got the nitty-gritty like hands-on research work with the work that you did in Oregon, mixed with really high level computational modeling, which, frankly, I haven't seen a lot of good integration of biology into climate models.

Vince Gauci:

So this was work that you were doing far before you started focusing on what we now know as the methane work and it's hard to do and I understand why people don't do that and quite often it's the last paragraph of a paper where it's an envelope calculation, and that never quite satisfied me. And the reason it's hard to do also is because these processes that we're discovering and then trying to highlight don't often operate in isolation. There's a number of different things going on, and so that becomes a challenge when you go up to the large scale. But yeah, you've got to have a go, I think.

Dan Goodwin:

And as we go into the technicalities of your paper, we're going to need to call in Paul Reginato, science Director of Homeworld, to help us work through this.

Dan Goodwin:

The one preface I would have, as we pass off, is that Paul and I both did our PhDs in a neuroscience lab, or we spent a lot of time in a neuroscience lab, and our professor there, ed Boyden, had this phrase which was always really funny, which was he would call it papers so scary that neuroscience promptly ignored it. So we have these mental models in neuroscience where things fire from axons to dendrites and then something shows that it goes backwards and everybody freaks out and ignores it. I wanted to say this to set up your paper when I was reading it, it just broke my mental model of how trees work and what goes into trees and how trees grow, and so I think, before we go too much in the technicalities, I would just love to hear your high-level story of what this work means and is and how we should think about it as we charge in, and then, after you finish that, we'll let paul jump in yeah, um, certainly so, this work.

Vince Gauci:

I think one of the things it does is it shifts attention in trees from the thing that has been the greatest focus, which is the photosynthetic apparatus that occurs in the leaves and that's quite rightly doing a huge job, to something entirely different, which is the tree stand above the bark surfaces, on the trunk and on the branches and down to the twigs, etc. And I think that was the moment when we realised, oh, there's something here beyond this discovery in itself. I think, once we realised that there was this huge real estate in forests that is vertical, I think that was an eye-opening moment generally for biology and, yeah, we do know things like tree bulb respiration happens and that there's things that we do appreciate, but it's relatively understudied given the the large surface areas. Essentially, just to give that high level overview of the work, we examined trees. We actually set out to look for trees that were emitting methane, and so this is a bit of an accident, in a way, and we patched together studies. That was done independently different PhD students, different postdocs from within my team that were working all the way from Sweden down to Amazonia and a couple of places in between and using those data.

Vince Gauci:

We're going to appreciate that upland trees on upland soils and I use the term upland as a distinction from wetland. That's the only distinction I make. There's a confusion sometimes in the UK when I say upland, I think it's up a mountain somewhere, but these are essentially trees on fruity draining soils that we thought it was worth a punt to have a look and to investigate those. And then it was about the uptake how much uptake there was. So we found a substantial amount and that's where the last four or five years has actually been about the scaling. We've had the data. Some of the data is like from 2013. We also plugged a gap in the methane budget to accommodate this sync term. There's some issues relating to the way the methane budget is calculated and this sort of helps that approach. So that was good.

Vince Gauci:

And then, of course, in in completing a part of the picture, the global methane budget we also then realized hang on there, this is an additional climate service served by trees and that's where it also got exciting and interesting and I think certainly a lot of the interest I've had since the publication has been from people who are interested in the direction that can take in terms of carbon credits etc.

Dan Goodwin:

Super interesting, and so, as we pass it over to Paul, I'm going to give it like a very pedestrian playback, which is that I always think about trees as sucking in nutrients and water from the roots and then photosynthesizing in the leaves, and what you're saying is that's a hyper simplistic model, because it turns out there's a metabolism in the woody surfaces that has significant climate impacts.

Paul Reginato:

Thanks, dan and Vince. Thanks, dan and Vince. Let's talk a little bit about methane and how it gets emitted, because I think when most people think about emissions, we're used to thinking about CO2 emissions, which come from chemical processes that humans carry out combusting fuel or producing concrete or producing chemicals. But that's not where most of the methane emissions come from, and the human impacts on methane emissions are largely not through those processes, but are through our impacts on other natural processes. So for our listeners who might not be familiar with biogeochemistry or with methane cycles, how should we be thinking about the methane cycle?

Vince Gauci:

The thing with methane is it's got a short lifetime, so around 10 years. It's very sensitive to the sources and sinks and that's why we're interested in characterizing those sources and sinks. And by far the largest source is natural wetlands. There was a recent study, though, which showed that about I think something like 20% of the natural wetland sources has been reduced from certain wetlands that have, particularly in temperate regions where it's they've been drained peatlands etc. And coming from the UK, certainly the east of the peat is being used for growing vegetables and salad crops. There's a use for that, and so there's been a lot of draining. But on top of those natural sources there's a little bit that comes from the marine realm, from oceans. There's other freshwater places like lakes etc. Don't count as wetlands, and there's other freshwater places like lakes etc don't count as wetlands, and there's some technical issues around how you characterize a wetland versus a lake, and it's about depth and all sorts of things like that. But then you also have natural animal emissions. So you have things like termites. They give off methane, but then you also have other ruminants in the wild. Animals give it off as well, and to some extent the the population of wild animal ruminants has sort of reduced a huge amount since we've encroached on, kind of been replaced on the great plains by things that eat grass that we then eat or drink, from cattle primarily, but also sheep are a significant source. So those are considered anthropogenic sources. And then you have fossil fuel emissions. You have fugitive emissions, things that come as a consequence of leakage from fracking, for example, but also natural gas pipelines that are a bit leaky, that haven't quite been tightened up. That comes out, and also just from our domestic appliances a little bit comes out as well. So, yeah, those are. And then there's landfill. Of course, waste management is a huge uh contributor to methane.

Vince Gauci:

As for the sinks, because we have to think of and I'll probably missed a few there, um, but as for the sinks, it's relatively simple, I mean up until this paper, and I'm sure there's going there, um. But as for the sinks, it's relatively simple, I mean up until this paper, and I'm sure there's going to be some people who are going to debate the findings that we presented in nature a couple of weeks ago. But it's simpler in that you only have the main one is the atmospheric sink, and that's the big cleaning agent, the big washing machine of the atmosphere and things like hydroxyl radicals, et cetera. They break down the methane in the atmosphere. And then the other sink is the soil sink. It doesn't change hugely. Yes, it will respond to things like changes in deposition of nutrients, like nitrogen, for example, changes in temperature. That will all affect the processes and operation in the soils.

Vince Gauci:

There's complexity across each of those sources and sinks. Now one of the challenges and I think just to get everyone up to speed a bit on some of the problems associated with this is the Global Carbon Project. Every year they'll come up with a new methane budget, along with other things, and they use a range of techniques to come up with the sources and sinks and they have what are called bottom up approaches. So that's assuming that we know everything that is going into the models and then building those up. So it's assuming we know the processes and it's taken them upscale. And then there's the top down approaches, which use a variety of integrative approaches satellites, chemical models etc. And those don't assume quite so much because they're integrative and that integrative global picture is smaller than the bottom-up picture. So in terms of sources and sinks and calculated things, that bottom-up approach either is missing a sink term or the sources have been overestimated, and so there needs to be some kind of reconciliation there between those approaches.

Paul Reginato:

I think it was great to hear about all the different kinds of sources and sinks from kinds of sources and sinks, and I think just to cover a couple key points that I extract there, I think a big takeaway about methane is that the methane sources are largely from landscapes, and so the human impact on methane emissions can be a little bit more out of reach in terms of our control, because it isn't like just stop burning a fuel. Right as we change landscapes, as we change the atmosphere, there are these relatively low flux but but very high surface area sources across landscapes that can go into the atmosphere, and this comes from biological activity right under mostly anaerobic conditions yeah and can I just add to that, because this has been a bit of a debate recently uh, in the sort of wetland methane world, in that the wetlands are responding to climate warming.

Vince Gauci:

if you turn up the heat on the wetlands, they'll be producing more methane and there's a danger there that we attribute the harm that results to the wetland itself, whereas actually it's amplifying the climate signal. That's the way I choose to look at it. I try to look at wetlands as a sort of an innocent ecosystem, if anything, that they've been hammered in the past and disparaged in all sorts.

Paul Reginato:

And the methane warming potential is also just, I think, a really important thing to highlight here. It's more potent than CO2. Over 100 years it's roughly 30-fold greater warming potential than CO2. But over the short term, like on a 10-year scale, it's something like 80-fold more potent than CO2. And the more methane we add to the atmosphere, the more we absorb the oxidative potential of the atmosphere, which actually extends the lifetime of methane. So this is a real, serious concern in terms of emissions and climate change mitigation. Let's talk about trees now. So Yafani's discussed the role of trees in CH4 fluxes, or CH4 being methane fluxes. So you initially were wanting to look at the emissions of methane from trees, which I think many of our listeners will be surprised that there would be emissions of methane from trees, and then what you found is that there's actually a sink in the woody surfaces of trees. So could you describe how do these processes work inside the tree? What should our mental model be for how methane emit from a tree or how it could be absorbed by a woody surface?

Vince Gauci:

Yeah, okay, yeah, definitely can explain those. So, yes, I focused on wetland trees to start with, and that was to solve another problem in the Amazonian floodplain, for example. We did that in 2017. We had a different nature paper out where we looked at that. There was an issue with top-down, bottom-up, albeit on a regional level.

Vince Gauci:

But these floodplain trees and trees that grow in wetlands they need to have oxygen in their roots, they need to survive, they need to get air down there and get oxygen down to their roots, otherwise it would be anaerobic and they would just die. So what happens is, with these wetland adapted trees, they develop these morphological features that allow for the gaseous exchange. So the by by morphological features, you might have seen some sort of the things called adventitious roots, which are roots that kind of near the surface or at the top or above, and they come out and they boost aeration. Also lenticels. So I don't know if you can see on the bark, especially on a relatively young tree, like a young cherry or something, you can see these little pores on the bark of the tree and that's part of the internal aeration system. But when it gets wet, you also get this tissue being called a renkema, and that tissue allows air to get in and down and into the roots. So that's the process of keeping the tree alive. The methane that's been produced in the rhizosphere, which will result from breakdown of carbohydrates, photosynthase, is allocated down into the roots and just leaks out as sugars and what have you? The methylogens will take those up, produce methane and then that just gets funneled out the other way Now, going upstream and away from wet environments into the uplands.

Vince Gauci:

The reason we actually went there in the first place is we thought four billion hectares of forest, the vast majority of it is upland forest, even if there's a small sort of production of methane in anaerobic micro sites in the soil, even though it's free draining, you can get these. Then if that isn't trained by the roots, maybe that's coming out. So that was the objective. That's why we went there. We thought a little but extensively emitted would be important and yeah, we found some being emitted at the very base, but then it was only when we started going up to about one metre. So in the tropics it was all uptake up to about one metre. So in the tropics it was all uptake, but at about one metre it switched one to 1.2 metres and went to zero and then it switched to uptake.

Vince Gauci:

It's unfortunate that the standard measurement high on tree trunks for processes in forest science happens to be what we call breast height. It's 1.3 metres. So if anyone's been doing that standard measurement's 1.3 meters, so if anyone's been doing that standard measurement 1.3 meters, that's the pivot point. That's where you're going to see zero, pretty much or not much happening. And it's when we got up to around two meters that we we saw a very strong signal, particularly in some of the locations in temperate ecosystems and certainly up in Sweden where it's cooler and a lot less going on. So we understood what was going on there. We were measuring this and it was a big surprise to us and we thought, okay, if you're upscaling from a source the smaller emissions that might be happening at the trunk base straightforward, because it diminishes quickly, it goes to, goes to zero.

Vince Gauci:

Straightforward. You treat the tree as a cone. We can add some metrics and upscale that. But once you get into this extra dimension and you find that the methane uptake signal strengthens the higher you go up the tree, that creates problems because you then have all the branches and everything else that's going on there, the twigs. Characterizing those areas is a challenge. But in terms of what's going on and what's determining that spatial pattern that we're observing, is that essentially you have those two processes in conflict.

Vince Gauci:

You have a small amount of methane production in the rhizosphere, in the soil, and you have methane uptake higher up in the tree and as you go higher up the trunk, the influence of the soil diminishes as the methane leaves or gets consumed and the higher you go the influence becomes on the methylotrophs that are inhabiting the tree surface and taking up the methane. It's likely the methylotrophs. We haven't actually characterized those individually. We have made isotopic measurements of chamber air that has been experiencing uptake. So normally in a chamber that's attached to the tree and that's how we measure the fluxes you would see an increase in concentration. That tells you there's an emission.

Vince Gauci:

But if there's uptake which is a bit more difficult to characterize because it tends to be a lower rate you see a decline and it's in that remaining air that we measured the isotopes, and the isotopes of the methane tended to be heavier and the isotopes of the methane tended to be heavier, which suggested that the methanotrophs were scavenging more easily the lighter methane it's something you see also in soils as well. So the lighter methane gets consumed preferentially, leaving behind heavier methane, and that's a pretty good signal that methanotrophy is taking place. So that's what's going on in both the wetland trees and in the far more extensive upland trees. And I should stress that the wetland trees fluxes, the emissions are huge, they're real point sources. It's a very tight area that you're considering, whereas for the upland trees it's a bit more difficult. It can be a bit more noisy, you're a bit more open to some sort of error in the measurements because you're operating at that boundary, just around ambient. But that's essentially what's going on. It's small uptake fluxes, but over an extensive area.

Paul Reginato:

Got it, and so it blows my mind that there are these microbes living in surfaces of bark that are able to consume such low concentrations of methane, where two parts per million is very low, and so these are really slow growing organisms that have really found a special niche.

Vince Gauci:

Yeah, it could also be that the microbes that are living there are doing something else entirely, but kind of opportunistically taking up the methane when it's available. So that's another thing that could be happening. There are esteemed microbiologists who are listening in on this who may have some interesting ideas on what's going on there. But yeah, you're right, slow-growing methanotrophs at Ambien. It's not what you would expect that way.

Paul Reginato:

So, yeah, okay. So I want to take us. There's two more points. I want us to make sure we hit before we move into audience questions, before we get to mitigation potential. I just want to get a sense for what is the remaining. What's the remaining work to be done on understanding the extent of this? In Bethane Sink, your paper, it said in the abstract. It seemed like you were careful to say these are some preliminary estimates of what the true role of trees could be. So it sounds like there's a lot of remaining work to to hone in on that and I think you're going to be doing some of that work. Yeah, absolutely.

Vince Gauci:

I have the editor to thank for for suggesting we tone it down a little in the abstract, and that was utterly fair enough. When we're presenting the world with a surface of exchange that's equal to the global land surface area and we've only just looked at this it means that we need more measurements and we need to do them higher up in the tree as well. Some of the measurements we did 11 metres. Very few measurements 11 metres within the crown of the trees. We also measured at five metres for some of the Amazonian trees.

Vince Gauci:

We need to do more measurements in far more locations and really it could be that by chance we've happened upon a bunch of trees that are happy taking up methane. It could be that there are others that don't do that and we know, for example, that in oaks in the UK where we've measured from those, it's next to nothing in terms of methane exchanges. It's very odd. So there is a huge variety, huge taxonomic variety of trees which may all have different influences, the traits of their bark If that's the habitat, what is it about that skin on a tree that is either helping exchange or reducing that exchange? Huge number of questions to go there.

Vince Gauci:

But the big challenge is doing measurements from a lot of trees at height. That's key getting up into the canopy. So one of the things I've got a project going on in it's about to start where we're going to go to Ghana. One of the questions we have is about the hydrology effects. That affects the interplay between any methane that's produced in the soil, but it could also affect the ability of methanotrophs on the surface If there's low humidity, for example. Are they going to be functioning as well? That's the kind of question we're looking at.

Vince Gauci:

And Ghana's great because you have over a few hundred kilometers. You go from humid tropical forest through to dry forest, then into savannah trees as well, but all at the same temperature. So hydrology is the one control that we can then disentangle. And also we decided we'd go to Ghana because it's Africa and there are no numbers in Africa, so collecting some data from there would be great. But we yeah, essentially we it's a call to arms to the community who make these measurements to go out there and make these measurements, because we really do need to refine this and and I'll add that we were cautious with our estimates. So the average that we measured at around two meters was what we plugged into our models that we then extrapolated from. But even in the Amazon trees, when it went up to five meters, we found twice as much methane being taken up. So there's potential for us to underestimate the sink as well as, you know, overestimating it for drier trees, for example as overestimating it for drier trees, for example.

Paul Reginato:

And some of these remaining questions also can relate to ways that we could leverage this right. Yeah, because some of the heterogeneity there, some of the factors that would make these estimations complex or require many measurements, could also be things that we could account for in our forestry and in the way that we cultivate trees. Let's make sure we say the number. So how big is this sink that you found? And then what's your estimate of how much it could be increased, let's say through land management or other kinds of choices we could make, and what are the levers that we would have to intervene on this?

Vince Gauci:

Okay. So there's a number of points there. So in terms of the size of the sink, it's uncertain and we had different estimates to come up with our broad uncertainty bands. But it's around 25 to 50 teragrams or million tons of uptake a year and, just to put that into some context, 50 is approaching 10 percent of the global sink term. The budget is roughly 55 to 60, no 550 plus thereabouts, and the numbers vary of emission and that's balanced by the uptake. So that's that number.

Vince Gauci:

And one of the questions we're seeking to ask, also through that project in Ghana, is whether deforestation has maybe increased methane by diminishing that sink. So that's a key thing we're looking at. But in terms of how we can, what levers we have, and and this sort of is more elaborated on in the ERL paper that was mentioned earlier, that perspective where I outlined some avenues of where we can harness this process the most obvious one is reforestation and that's key. And one thing that's really good about this is that for natural forest regeneration, especially trees that don't grow too fast, a young forest stand, you will have lots of young trees that take a long time before they start accumulating the carbon that you find in a mature forest stand. But because of the nature of topology, even though they don't contain much carbon, they will have almost a very similar surface area. So if that surface area is colonized relatively quickly by the sort of microbes that are forming this function, then it's possible that we have a faster climate win by taking up methane before the carbon accumulation really kicks off down the line. So that's useful to know In terms of other very happy to have recently secured a SPARC exploratory grant.

Vince Gauci:

So thank you for that. The SPARC team who are out in the audience and we're really excited to. This is proof of concept and we're really excited to. This is proof of concept. There are many things that we think we can do to move some levers to try and enhance methane uptake, and one of the things a couple of things we're going to be doing with the SPARC grant is, just as a proof of principle, to see if there's somehow some nutrient limitation on existing methanotrophs in certain environments and if we can lift that nutrient limitation for those already there, if that can improve their function. The other one that we can do is look at this let's get some methanotrophs and just add them. It's's a brutal approach but again as a proof of principle, to see if that kind of phyto microbiome engineering but without going down at the molecular level on the microbes, but just seeing if existing communities that we can access, if we can add those or encourage those, if that can also boost uptake. And I should add also that these approaches, essentially if you're playing with or manipulating the microbiology of the tree that's part of the ecosystem, the natural place to do this would be on commercial forestry plantations and to really look, because there's a especially in terms of the carbon that they take up.

Vince Gauci:

For certain species acacia or pulp paper type tree species you know that they're essentially co2 neutral. They'll take up the co2. After their cycle of growth they will be turned into paper and a few years down the line that then goes back into the atmosphere. But the difference here now is that we have that surface area that could be harnessed while they're growing. So that's another thing that we're looking to investigate a bit deeper. You had a number of points. I probably didn't cover them all.

Paul Reginato:

That's all right, vince, we're blazing through here. There's so much to cover and I really love this conversation. You've uncovered something very new here and there's a lot of really cool directions to go. I think now we're going to switch modes to taking some questions from the audience. There's been questions streaming in throughout the conversation, and so I'll hand it over to Dan now to pose an audience question.

Dan Goodwin:

Awesome, vince, this is so cool. I just want to echo what Paul is saying. The reason this is such a great topic is that it makes every biotechnologist in the audience think oh wow, here's these tools. I know how to study biology. Now there's this new phenomenon we've never thought about. So bravo, it's really cool. I'm going to try to clip this through a handful of questions, so we're trying to go for speed to get as many, and I think everyone's going to leave with more questions. I'll try and speed up my answers. How dare you have good things to say? So? How does nitrogen deposition in forest areas, such as from urban air pollution?

Vince Gauci:

impact, methane cycle and uptake from trees. That's actually a good question, because methanotrophs are also implicated in the N2O cycle, so we don't know there could be like a pollution swapping effect or there could be some kind of effect whereby the methanotrophs start giving out N2O and that would be a bad thing. Right, that's even more powerful as a greenhouse gas than methane and I think Mary had a paper out in Science recently tackled this question brilliantly. I think Mary had a paper out in science recently tackled this question brilliantly and really highlighted the issue of of nitrogen and trying to manage for one could create a problem for the other. So, yes, but equally, we know from rice paddy soils that some methanotrophs are nitrogen limited, so they're not substrate limited and so that nitrogen limitation could be lifted if that's what they're limited by on trees, and that could increase their methane uptake. Again, there's a number of ways this can go and it's a question of going out there and actually measuring what's happening.

Dan Goodwin:

Great, I'm forcing myself to continue going through questions because I would love to ask some questions there, but we're going to keep going through. A great question is could this phenomenon be driven by the methanol being emitted by bark being emitted by bark?

Vince Gauci:

It could be. Yeah, like I said earlier, I think there's the chance that the methylotrophs that are on the bark or within it are actually specialized or doing something else, and it could be that they're consuming methanol, for example, and then the lower concentrations of methane that are not so abundant in the atmosphere they come across it and they also take that up.

Paul Reginato:

sure, that's a great hypothesis to test so I'm going to jump in with one here. So there are other surfaces to trees other than woody. Right there's leaves, and I have seen some literature suggesting that there may be a methane uptake in leaves and there's other plants that are not woody that have a lot of surface area. Do we know about the methane flux on these other surfaces and how might they be contributing? Is there a chance that there's an even greater methane uptake or in what direction do we expect? Yeah, would it could.

Vince Gauci:

you're absolutely right, and there was a paper not long ago, uh, from a canadian team who a really interesting study where they um looked at leaves, uh in deciduous forest and they measured uptake um. I always caution whenever we apply the techniques that we use for things like stem surfaces or soil surfaces, because there's a real challenge once you get into the canopy especially, and you have high light levels and you have the photosynthetic apparatus of the tree is there and it's doing what it does and there's transpiration photosynthesis there and it's doing what it does and there's transpiration photosynthesis and there's always the worry that the chamber that you're putting on the leaf to make the measurement is in itself altering the conditions, which in itself is altering the, the variable you're interested in and and I know there's teams in finland marie pilati is one and there's a number of other teams where they've you have to modify for things like to keep the climate, the temperature, the same here, temperature can skyrocket. In these things you have a greenhouse, essentially. You know that. I think that is the big challenge and it's also something we've been thinking about for a long time, because I don't know if any of you I suspect most of you were probably in school still, but back in 2006, there was this sort of seminal paper that fascinated a whole community and that was this paper by Frank Kepler. Again, it was in Nature and the idea was that all green things, essentially, was producing methane and was giving it off.

Vince Gauci:

And it's been a real challenge to make those measurements on those even ordinary sort of herbaceous plants at ground level, to say nothing of getting up into the canopy and measuring from a large number of trees. So I say that the jury's still out and, just like I'm saying, for our study with the stems and the trunks and the branches, we need more data. But I think this is a real uncertainty and a real unknown. And if it's a microbial issue and if there's slow growing, methanotrophs for example, it could be that deciduous trees just aren't capable of building that population quick enough in order to have an appreciable effect. But it gets really complicated once you get into the leaves.

Vince Gauci:

And I will say that Frank Kepler's team have been amazing. They've produced a lot of really excellent work and they've also identified production in most living things. I've called what they call it, but there's a term they have for it, but I always argue that if there's methane being produced. That's a meal that's too good to miss in in the ecosystem, so you will find the methanotrophs there, and that's possibly why we don't see appreciable emission from upland trees. There's some will, and that could be a termite or something.

Dan Goodwin:

Let me just punt to one more simple, short question before we go to some rapid fires, which is that are there clear types of trees that you think should be prioritized?

Vince Gauci:

It's good you mentioned that.

Vince Gauci:

I'm of the opinion that if you're going to reforest, natural regeneration is probably the most effective way to do that, and that's normally a broad assemblage of trees. And certainly for carbon uptake in trees, some evidence suggests that mixed stands perform better than monoculture stands, so that could also. I don't have a hypothesis as to the mechanism behind it, but that could also be something that's going on. I will say, though, that for the trees in the Amazon, if you're going to go and select trees, the average that we used from around two meters I'll call it 50 units of uptake 50 micrograms per meter squared per hour of uptake was what we used, but we did find trees that had five, six times as much uptake.

Vince Gauci:

The answers aren't necessarily all about prodding a tree with additional methanotrophs or additional nutrition. It could be about understanding the traits of that tree. Why is it that individual species is taking up five, six times more methane than the average that we've found, and how can we harness that? So, to answer your question, if you want natural regeneration or you want to encourage some planting and you want to manage for methane, which is a supplementary question here then I'd be looking at those natural tree species.

Dan Goodwin:

Fantastic Vince. This has been so much fun and we want to wrap with four rapid fire questions that are zooming out of the tree question for now and also just for you as a person who's done beautiful work and really impactful work. So I'm going to ask you the first one, which is that can you remember one article, personal result or idea that totally changed the way you think about biology? Okay, rapid.

Vince Gauci:

First thing that comes to my mind is it's actually not a paper, it's. I think I was a 12 year old and I came across JE Lovelock's Gaia Hypothesis, which was a book, and it caused me to look at biology in entirely different ways. A 12 year old considers biology, but in this case it was wow the whole earth system and the knock-on effects and the feedbacks and that I think that is something that actually is carried with me throughout.

Dan Goodwin:

I love it. So second question what's the best advice line that a mentor gave you?

Vince Gauci:

Okay, I'll do two things. I'll answer that question, which was the one that sticks in my mind, is David Fowler, who was one of my mentors, and I gave a horrible talk once as a PhD student in Denmark for this workshop this like training workshop. It was horrible and it was partly horrible because I didn't analyze my data correctly and it was a mess. And it was a mess and I was hugely embarrassed and he just said to me Vince, it's fine, it's fine, this happens to everyone. Prepare, and I've tried to do that ever since I've just I have his voice in my head before at all. Can I just add the second one, which is me as a mentor.

Vince Gauci:

What I tell some of my PhD students and that's the tendency to overwork is in our culture, and I think that has potential to limit the space for creativity sometimes. So I do make sure that they stop at a reasonable hour. They get things done, but they take their breaks. They have their holidays. They lie on a beach somewhere with a trashy done, but they take their breaks. They have their holidays. They lie on a beach somewhere with a trashy novel. They do that sort of thing, and I think that's something that they tend to have appreciated whenever I've said that.

Dan Goodwin:

That was the third question I was going to ask, and if you weren't already about to be inundated with PhD applicants, I think you definitely will be now, and so the last question here is that and I think this is going to be a very obvious answer but if you did have a magic wand to suddenly get much more attention and resources into one part of biology, what would it be?

Vince Gauci:

I think it's the large unknown world of tree bark. It's got a surface that has had some study. Of course we know some important things about it, but it's clear we're barely scratching on the surface, so I think that's where it's got to go. I'm totally biased there.

Dan Goodwin:

And that is a fantastic end on. So, vince, thank you so much for taking time to educate us and entertain us with your stories and really to inspire, showing that you can do things that go from the molecular scale metabolisms to the Gaia scale models, and you can do the whole thing while reading trashy novels on a beach. So that's fantastic. And so please, for everyone here in the audience and for everyone listening, let's please say a huge thank you to Vince for hanging out with us.

Vince Gauci:

Thank you for having me. It's been a real pleasure to share the work. Vince, for hanging out with us. Thank you for having me.

Dan Goodwin:

It's been a real pleasure to share the work. Thank you so much for tuning into this episode of the Climate Biotech Podcast. We hope this has been educational, inspirational and fun for you as you navigate your own journey and bring the best of biotech into planetary scale solutions. We'll be back with another one soon and in the meantime, stay in touch with Homeworld Collective on LinkedIn, twitter or Blue Sky. Links are all in the show notes. Huge thanks to our producer, dave Clark, associate producer Arya Natarajan and operations lead, paul Himmelstein, for making these episodes happen. Catch you on the next one.