Sustain Episode 2: Can planting more trees slow climate change?

Transcript

Maria Armoudian: Hello and welcome to Sustain! The podcast of Nga Ara Whetu: Center for Climate, Biodiversity and Society, I’m Maria Armoudian. Governments and others have advocated to offset carbon emissions by planting more trees, but is this really the long-term solution? Our experts say it won’t be enough, and in some cases, it can make matters worse. With us are three experts from the University of Auckland.

MA: Kevin Trenberth is a professor of physics studying climate change. George Perry is a professor of ecology. And Cate Macinnis-Ng is an associate professor of biological science. Welcome to Sustain! Thank you so much for being with us here on this new podcast that we’re doing. And we want to understand some of these processes and what’s going on with climate change. I thought, Kevin, we would start with you. What are we up against now in 2023 with climate change? We’ve seen the weather. We’ve seen the storms. It looks really awful. What’s the scenario?

KT: Well, climate change is happening, mainly because of humans changing the composition of the atmosphere. Emitting carbon dioxide and other greenhouse gasses produces a warming effect. Pollution of various kinds blocks the sun and can produce cooling effects, but it’s much more regional and adds considerable complications to the climate change. If you look at the carbon dioxide record in the atmosphere, it’s going increasingly upwards.

KT: All of the Kyoto Protocol and then the Paris Agreement was designed to bend that back down and there is no sign of that happening yet. And so, although quite a number of countries around the world have decreased emissions, New Zealand has decreased emissions somewhat in the last three years, or four years or thereabouts. Not a lot, but, you know, a little bit. And many other countries have too. But it’s all been overwhelmed by huge increases from China and India in particular, a little bit from Russia. And so other countries are not necessarily helping in this regard.

KT: And so climate change is with us, it produces extra heat. The oceans are warming as a consequence. The oceans are at their warmest point ever on record for the top 2000 meters. We can track it very well now. And the sea surface temperatures are at record high levels. The atmosphere has also been at record high temperatures over the last four months in particular, and there are melting glaciers, Greenland, Antarctica, putting more water into the ocean. The ocean is expanding because it’s warming up. And as a result, sea level is rising.

KT: This threatens all coastal regions. Anytime there is a storm nearby, the storm surges are worse than they were before. And erosion is much greater as a consequence. In general, because of the high temperatures over the ocean, there is more water vapour in the atmosphere. Water vapour is a powerful greenhouse gas, and it amplifies the climate change. That’s one of the things which is accelerating the climate change in some sense. And the water vapour itself gets caught up in storms. It means it rains hotter. When it rains, the storms are more vigorous than ever before, but at the same time, a lot of weather continues, much as it has before. Natural variability continues as it has before.

KT: But the consequences of both the weather and the natural variability are greater than they were before. And so now we’re going from a La Niña over the past three years, up until the end of, say, April this year. And we’re now in an El Niño going on. And so this very much affects the patterns of weather around the world and especially across New Zealand. Let me pause there.

Maria Armoudian: Since you mentioned La Niña and El Niño, you might want to explain what those mean for people who don’t know.

KT: El Niño refers to a warming of the central and eastern tropical Pacific along the equator, all the way from the dateline to the Americas. It covers a huge area. It’s actually an area larger than North America. So, it’s a big hunk of the ocean. And when those conditions are cool, as in a La Niña, that means the weather is not occurring in those regions.

KT: And in an El Niño, all of the thunderstorm activity and tropical cyclone activity gets attracted into the central and eastern Pacific. And so that affects the middle and high latitudes with regard to the jet stream and the storm tracks, it has what we refer to as teleconnections around the world. These are connections related to what’s going on in the tropics, and they can be quite profound.

MA: Let’s turn to George Perry. What about fire? We’ve heard about the rising sea levels. We’ve heard about the weather patterns. We’ve heard about the storms. What about fire and climate? What’s that relationship?

George Perry: Kia Ora. Fire has been a really important part of the Earth’s system for several hundred of millions of years, since plants moved onto land, and there were changes in the atmosphere, increasing oxygen levels and so forth. And so, just as climate has varied naturally over time, so too does fire activity through time and space. If we look at the fire triangle that we learn at school, we’ve got oxygen, fuel, and ignition.

GP: If we put oxygen to one side for now, we’re definitely changing patterns of ignition, both through human land use, urbanization and so forth. But also, there’s evidence of catastrophic shifts and lightning activity shifts from wet to dry thunderstorms as a result of climate change. And climate is undoubtedly driving changes in the nature of the fuel itself. So, it’s drying the fuel out.

GP: And basically, what drives most wildfires is, how dry is the fine fuels? Things that are skinny, like sticks and twigs and bits of grass. They have an equilibrium moisture content and under warmer conditions, and some starting earlier, going later. We’d expect more fuel to be dry for longer, basically. It’s fair to say that the patterns of fire activity are very variable.

GP: So although we see that in Canada this summer, austral summer, in parts of North America there were very large fires and fire frequencies increased in the west of the US due to drying. In Africa, we think that over recent decades fire activities actually declined and that’s because of widespread transformation of agricultural land to urban areas.

GP: And so it’s not as simple as it gets hotter and drier. We get more fire. In some ecosystems we’ll actually expect, as it gets hot and dry, fire to drop because there will be insufficient fuel to carry fires. In some settings we’ll expect fire to become more common as fuels become drier and there are more ignition sources available. The main concern we have ecologically is that plants aren’t actually adapted to fire per se, they’re adapted to patterns of fire. What we as ecologists call a disturbance regime.

GP: So many plants, for example in Australia, are cued into a reasonably predictable interval between fires. They accumulate seeds, they may flower in response to smoke or so forth, and plants just can’t keep up with the rate of change. If we have plants that are used to fire every 15 years, that’s what they’ve evolved under, and it suddenly becomes every five years. Then they’re simply not going to be able to regenerate. And that’s what’s led to concern about things that have been in the media recently, the risk of a wholesale tip of Yellowstone into a grassland, the collapse of the Amazon with associated changes in global circulation and so forth.

MA: What about the other way around with fire affecting climate?

GP: Fire affects climate at multiple scales. We know that individual fires are perfectly capable of generating their own weather. And so, we have these spectacular pyro cumulus clouds that occur when there’s huge convective activity around fires, but fire, and it’s not really my expertise, fire climate. We know that in some parts of the world the presence of smoke particles and ash in the upper atmosphere can inhibit things like cloud formation and change patterns of rainfall.

GP: And as Kevin said, there are pretty strong positive feedback loops between fire, deforestation and climate. So, they’re interacting alongside each other and amplifying each other. So, if we have a fire and that results in forest being replaced with more flammable material, in a drier climate, we get more fire, so we see these positive feedback dynamics driving forest systems to non-forest states. That could be very difficult to reverse.

MA: That sounds like a perfect cue for Cate McInnes-Ng. What are these climate relations with forests and biodiversity?

Cate Macinnis-Ng: Kia Ora Maria. Perhaps if we go back a step and think about what forests can do in terms of addressing climate. Any photosynthetic material, any kind of plant -type biology is able to take up carbon from the atmosphere through the process of photosynthesis. And so, this includes forests as a big example of that. But actually, all plants will be taking up carbon, that includes aquatic plants.

CMN: Seaweed, seagrasses, forests, savannas, grasslands, all kinds of plants are taking up and.

MA: And storing.

CMN: Taking up and storing the carbon.

MA: Holding it so it doesn’t go into the atmosphere?

CMN: Yeah, that’s right. We talk about fluxes and stores of carbon. So fluxes are the processes of uptake and loss and a nice old-growth forest is generally in kind of equilibrium, where it’s maybe taking up as much carbon as it loses each year and the loss is through processes of respiration from the plants themselves and also from soil microbes and other things in that system. And then the uptake is all through photosynthesis.

CMN: We think of forests a lot in this kind of space, because as aboveground ecosystems they store a lot of biomass, they have a lot of biomass. So, if we compare a forest to grassland, you can see there’s a lot more material there in the plants and so they’re storing more carbon. But what we shouldn’t forget is that it’s not just what’s above ground. There’s also a lot happening below ground. And so, some of the grass-type systems, the tundra in the colder parts of the world, they’re really carbon dense below ground as well.

MA: So, if you disturb the ground, you also release carbon.

CMN: Yeah, that’s right. So, when we’re thinking about how we can address climate change, we often talk about planting trees. But in fact, maybe conserving other ecosystems is just as important because those are carbon stores that are already in place, and we should be making sure that we look after those as well. This is all part of this idea of nature-based solutions where we think about not just trees for carbon, but we think about whole ecosystems, we think about the other services they can give us. And this includes things like water cycling, preventing floods and providing habitat and food for biodiversity.

MA: Well, since you mentioned planting and the storage of them, that has been one of the solutions that has been proposed. But it seems like it can sometimes be a problem. Is that right?

CMN: I don’t know if we want to say it’s a problem. I’m always a big fan of planting trees, but I think we need to be thinking about the fact that there’s a limit to how much planting can help us in terms of addressing climate change. Really, we should be thinking about reducing emissions as the front-line approach. And then any planting can give us some extra support. And obviously too, like I said, we need to be conserving and looking after those existing carbon stores as well.

MA: George Perry, what would you add?

GP: Yep, Cate. I think from my perspective, it’s a matter of the right tree in the right place. We have natural globally grassland ecosystems that are under threat from trees, so going and planting trees in prairie habitats is probably not a particularly good idea. We have complicated dynamics around invasive plants, New Zealand is heavily invested in Pinus, which ironically perhaps is critically endangered in its native range.

GP: But we spend a lot of money, millions and millions of dollars trying to control it while also planting it for carbon sequestration. And I think the main point I’d echo that Cate made nicely is that we’re not going to sequester our way out of this problem. If we don’t deal with emissions, then this isn’t really a solution, I don’t think.

KT: Firstly, just with regard to the disturbances in soils, we might add to what Cate said, something about permafrost, because permafrost has a lot of vegetation matter frozen below ground and a lot of it is thawing. And as it comes out of the ground, some of it will come out as carbon dioxide, effectively, if it’s dry enough and there’s enough oxygen around, but more likely it comes out as methane. And so, there’s the potential release of methane, which is a very powerful greenhouse gas.

KT: The second point relates to some of the discussion that was just initiated, but nobody actually mentioned this term offsets, and trees can be a good short term offset, but trees have a finite lifetime. And as was mentioned before, an old-growth forest is actually neutral with regard to carbon dioxide. It takes up as much as it emits back into the atmosphere as leaves fall on the forest floor and twigs, and trees die and they emit carbon dioxide back into the atmosphere.

KT: The other aspect that I thought I would comment briefly on is the use of monocultures, which has been a substantial issue, and especially with some of the wildfires in Canada recently.

MA: Oh, that’s actually a great place, because I wanted to talk about Canada. I think I have shared with you all a piece that ran in the New York Times about, not just the fires, but it said that Canada’s forests have emitted more carbon than they’ve absorbed since 2001. What’s going on here?

CMN: This is all about the fluxes that are happening in the forests, and I think what we’re seeing with the change in climate, there’s a number of factors that influence the fluxes. One of the big ones is, as temperature is increasing, the rate of respiration is also increasing. Photosynthesis does increase too, but respiration is increasing faster. And there’s been global studies to establish that that’s consistent across all planted ecosystems, that this increase in respiration is outpacing the increase in photosynthesis.

MA: And the respiration is the emitting of?

CMN: That’s the loss of carbon back to the atmosphere and that’s often driven by the heterotrophic respiration and that’s the respiration coming from the microbes in the soil. It can also be to do with enzyme processes being sped up, but there’s a lot of different factors that really influence that. So that’s the first thing, that’s the effect of temperature.

CMN: Then we’re also seeing other things like extreme events. We’ve talked about fires, but also droughts can have an influence on fluxes of carbon. For instance, I’ve got some data showing that kauri forest flips from being a carbon sink to a carbon source during drought years. By that I mean during the good years when it’s nice and wet, kauri will be taking up more carbon than it’s losing.

MA: And kauri is an indigenous tree here in New Zealand.

CMN: That’s right, and they grow for a very long time. A thousand years or more they might live to, under the right conditions, and under those good years it’s a carbon sink. But then during drought years we’ve found that the system becomes a carbon source because kauri is drought deciduous, so that means they lose their leaves as a response to the drying soils.

CMN: And that’s a strategy to save water so that the plant will survive the drought. But that extra leaf litter going into the soil then creates more carbon going back to the atmosphere as that leaf litter breaks down. So, what we don’t know yet is, what’s the limits to that? How bad does the drought have to be for that to be an issue?

CMN: We don’t know much about the recovery processes, so we know that if we look at annual carbon budgets, we can pick this up. But perhaps in subsequent years it’s accounted for quite quickly. But we do know that droughts are becoming more frequent and more severe, so likely to be an issue.

MA: Anything you would add George Perry?

GP: The Canada thing, it was brought to the fore really by Canada worrying about whether it was going to meet various carbon accounting protocols. And I’m not sure how surprised forest ecologists in Canada were about this. About 15 years ago, the Canadian forest, which is largely boreal, very large expanse of forest, tipped from being a sink to a source. The first decade of that was almost certainly insect outbreaks, which may have a climate relationship, it’s not very well understood.

GP: And then fire. And so, part of the issue around the very large fires is not just that they kill trees, but the carbon’s released extremely quickly compared to the natural rate of release in a forest. We see a change in the rate that carbon is being released. Canada’s plantation forests are actually still a net carbon sink, a very small net carbon sink, and that’s driven by ongoing planting.

MA: When we’re saying carbon sink, we mean that they are holding carbon, rather than releasing it into the air, storing it within themselves.

GP: Yes, so they’re a small sink, driven by replanting and also the rate of carbon release from wood products is slower than in a fire. So, the rate at which carbon is returned to the atmosphere is quite an important part of the process. It’s been a very steep decline in Canada’s forests. There’s a lot of concern in North America about links between forest insects and fire, and a lot of debate about how they are linked. But yeah, that’s sort of where we’ve ended up.

MA: You also mentioned, George Perry, about invasive species, and I had read that in Hawai’i, those fires were partly because of an invasive grass. Is this something that should be addressed? What’s that relationship that we need to know?

GP: In Hawai’i, again, it’s been known for a long time that in some of these shrublands, fires don’t spread necessarily well, because the shrubs are separated. And so when you get, in these more semi-arid environments, grass in, it connects it up and burns. In Hawai’i, there’s also, as in much of Polynesia and the Pacific, been long-term degradation and fragmentation of wet forest, which acts to dry it out and make it much more vulnerable to fire in general.

GP: So, it’s a combination of invasive plants, fragmentation of forests, humans more in the environment and that sort of thing. Invasive species clearly have a role to play, but even without them, I suspect we’re looking at, just getting rid of invasive plants out of these landscapes, isn’t going to mitigate the entire fire hazard that we face. And as I said, the irony is some of these invasive plants are also commercially extremely valuable. And so, it’s a trade-off.

MA: Which actually brings us to the issue of commercial logging. Does that play a role in all this?

GP: In New Zealand there’s very limited commercial logging of old-growth conservation estate. New Zealand has a weirdly binary set up. Clearly in a production forest environment, there’s a balance between what you plant and what you chop down. If you just chop down all your trees and don’t plan them, it’s not a particularly good business model. So there are probably market norms that drive you towards a sort of carbon equilibrium.

GP: But as Kevin said earlier, widespread deforestation is definitely problematic. If you are removing trees en masse from the landscape, as in the Amazon, then that is going to change the climate with flow-on effects to biodiversity and fire. If you’re carefully removing a single tree with a helicopter, that’s quite different.

MA: Anything you’d add on that Cate Macinnis-Ng?

CMN: Forestry isn’t necessarily a bad thing because what you’re actually doing is taking up carbon and storing it into wood. And if that wood is then used to make furniture, for instance, then that carbon is kind of locked away. It really depends in some ways what that forestry is being used for. If we’re going to think about the kind of role it can play in carbon mitigation.

MA: So, if you do turn it into furniture, it keeps the carbon in it?

CMN: Yeah, that’s right.

GP: Until it rots away.

CMN: Yes.

GP: I think the key to remember is that commercial forestry has an economic imperative and it’s not necessarily storing carbon, it’s returning money to shareholders, all the things that go on in the sort of markets we live in. So, there’s going to be a trade-off between those demands, environmental demands, climate demands.

CMN: Yeah. And also, other ways that we might use the land.

GP: Yeah, the opportunity cost of having forest there.

KT: The big picture is that about half of the emissions that are coming, mostly from fossil fuels, that go into the atmosphere are carbon dioxide, end up in the atmosphere and about 25% to 30% goes into the ocean and part of that causes acidification of the ocean and the other 25% or so evidently goes into land. It’s not as well-documented as we would like, but it does relate to this so-called fertilisation effect of carbon dioxide. And so, it does mean that trees can, and other plants can grow a little faster or more than they would have otherwise.

KT: The biggest risk near to us here in New Zealand is actually from wildfires in Australia. And the best example of that was in the summer of 2019-20, which was a relatively weak El Niño condition. And as I mentioned before, we’re moving into El Niño conditions now. The risk of wildfire in Australia is much above average as a result and a number of times in early 2020, I think it was, there were plumes of smoke that came all the way across to New Zealand and here in Auckland we were bathed in smoke for a couple of days.

KT: So, the prospects of that happening this coming summer are increased over what they have been over the last three years, in particular. I think the way to think about it is that there’s a risk of wildfire. Whether it actually eventuates or not depends a lot on fire-fighting capabilities and prevention. And I’d like to hear the other guests actually talk a little bit about that and the use of firebreaks and proper management of forests.

GP: Thanks Kevin. I would also say that there’s been quite a lot of work done in Australia and California, around the fires in the 2010s and 2020s. The indirect costs of wildfires dwarf the direct economic costs. The public health burden in south-eastern Australia of the large fires, the cost to tourism, the other costs to infrastructure, are enormous.

GP: So, when we think about, say, increased wildfire risk, there’s a lot going on besides the loss of natural capital that we need to be aware of. And these things are all coupled into each other. In terms of managing fire risk, New Zealand has a complicated association with fire in the sense that, prior to human arrival around 750 years ago, fire was quite infrequent, it wasn’t absent, but it was infrequent.

GP: And we know that from sedimentary charcoal and pollen records, it was concentrated in the eastern parts of both islands. And we believe the reason for it to be rare was simply there wasn’t an ignition source, there wasn’t lightning of sufficient frequency to trigger large fires. When people arrived, Māori and then Europeans, they brought fire with them and transformed the landscape.

GP: Nevertheless, New Zealand still has, globally, extremely small fires, the average fire size is less than ten hectares still, but it’s clearly growing. We’ve already had a fire in the Mackenzie Basin this summer. We’ve had fires in Northland in the last few years, so the fire threat in New Zealand is growing. The question of how to manage it is a complicated one.

GP: Traditionally we’ve run around and tried to put fires out. A very suppressive policy and I think that’s because New Zealanders see fire as a land-use tool, not an ecological agent. In places like Australia and in North America, fire suppression is a much more debated activity. Really the question is, how long can we just run around with hoses for? Are the other ways that we could stop fires?

GP: Especially with my colleague Tim Curran at Lincoln, we’ve been looking at ideas like green firebreaks. So if we can identify low flammability fuels, can we plant them in strips in the landscape to act as green firebreaks with, potentially, co-benefits, such as Cate was talking about before, to do with biodiversity, habitat provisioning, pollinator services, and I guess probably not a large amount, but a contribution to carbon in the landscape.

GP: I suspect that we are going, in New Zealand, to have to get used to living with fire in a way that we haven’t in the past. We’ve focused a lot on tectonic and seismic events, volcanoes and earthquakes, but I suspect that we will have to adapt to live with fires in a way we haven’t before, especially in what people call the wildland-urban interface.

GP: The Port Hills in Christchurch is a good example, but the Mackenzie Basin has urbanized a lot in recent decades, and those are very fiery parts of the landscape. And where we have people in the landscape, and infrastructure, we’re likely to see fire. So, it’s a way we have to face to adapt to that, I think.

CMN: I think we’ve got to adapt to a few other things as well. I mean fire, big one, but also mentioned drought already, cyclones, got a lot of things to adapt to. Plenty of ways we need to be changing how we live and do things.

GP: Yeah, I completely agree Cate. I wouldn’t say fire is the only thing, especially in New Zealand. It’s one that’s getting a lot of activity. But if you think about New Zealand for humans, probably things like sea level rise and I was recently reading about insurance retreat in New Zealand.

MA: It’s happening all over the world.

GP: Insurers walking away from insuring high-risk locations. How is that going to play out?

MA: It’s happening in other parts of the world.

GP: There’s fire retreat in parts of the world, but I suspect in New Zealand that’s a long way off.

MA: Many countries have looked at trading schemes and offsets and all of these. But we’ve already said in this conversation that you can’t really trade your way out of this. You can’t really store your way out of this. You’ve got to reduce emissions. What are the ways forward in addressing climate change and what is the role of the natural world?

KT: The main strategy is certainly to decarbonise the economy. That means especially trying to cut down on the use of fossil fuels of all kinds, especially coal. That often relates to industry and coal-fired power stations. We have Huntly here in New Zealand, which is burning coal and I think it should stop, quite frankly.

KT: So decarbonising, that means electrification of a lot of things, like our vehicle fleets. The incentives are in place to increase electric vehicles in many places around the world, it’s especially going quite strongly in China. And I think we’re going to be seeing a lot more EVs from China in New Zealand, but they’re growing enormously in North America as well at the moment.

KT: This brings with it other kinds of issues about; can we generate enough electricity? This is an issue for New Zealand. Can we move it around with transmission lines and can we do it renewably? That is, can we use hydro, solar and wind power, especially, and how do we put those together in ways which make a more integrated system?

KT: I think this is actually a major issue for New Zealand. It’s something that is not being done at all well now, and New Zealand is way behind in terms of things like rooftop solar. Rooftop solar is picking up enormously in Australia, but they were very far behind and there’s been a big change going on in Australia since the change in the government and the Labor Party came in. But these are all substantial issues about, can we decarbonize our economy in various ways?

CMN: Totally agree with what Kevin’s saying around the challenges and opportunities of decarbonizing, but it’s a really important thing to happen. But when we’re talking about decarbonizing, say for instance, if we do shut down the Huntly coal power station, then that stops the carbon going into the atmosphere straight away. Whereas the difference with offsets is that there’s a lag time between the carbon being taken up and our planting.

CMN: So, if we’re planting trees as offsets, we put tiny baby trees in the ground. They take decades to grow. During that time, they are continually taking up carbon as they photosynthesize and they’re increasing their store. So, it’s all a good thing. But as I said, there’s this lag time, so we can’t actually hop on a plane and use the offsets and think that, oh, it’s all being sorted out, because the carbon is already into the atmosphere. As soon as we’ve had that plane trip. But it takes a while for those trees to take up that carbon. So, it’s another reason why we can’t be relying just on offsets.

MA: And sometimes they’re releasing carbon, both in the dropping of leaves and twigs, but also when they’re burning down and that sort of thing.

KT: Perhaps we should also talk a little bit about biofuels at this point. And so wood is a potential biofuel and that’s one way actually you can replace coal in some places. The potential for using woodchips, high quality woodchips, for drying milk, for instance, in Fonterra, and even in Huntly, I think they’re importing some woodchips. But these are highly processed woodchips, torrefied wood, where the moisture content has been reduced and there’s no factory in New Zealand that can even produce these right now.

KT: And it’s the sort of thing we could even export because of the need for fuel in winter in Europe for instance, since it’s not coming out of Russia now and there hasn’t been any discussion about these kinds of things, or no adequate discussion. And in the meantime, you see all of this slash and the damage from slash that has occurred from wood that has been left behind after the major culling of and harvesting of wood.

CMN: I wouldn’t say biofuels are my area of expertise but some thoughts on the, I mean really good points Kevin about how we need to be doing some creative thinking and we also need to make sure that our processes are, I guess, as efficient as possible, sustainable. And, you know, thinking about how we’re doing harvesting and things is a useful approach to take. But is slash something that you’re suggesting should become a biofuel?

KT: I don’t fully understand that, but I don’t think slash should be just left behind like that. It ought to be processed and it could be processed into woodchips of various kinds. It has extra cost for those who are trying to raise trees for wood logs that are exported to China. And quite frankly, I hate to see that. I would much rather see much more processing going on to higher level products within New Zealand, because one of the things which is going to be a major challenge as we move into the future is the whole cost of shipping, exports and imports, are going to go up because of the cost of carbon, because of the cost of moving things by either ship or by airplane are likely to increase because of the decarbonisation process and tariffs and other things like that, that get put in place.

MA: Well, why don’t we do one more round of, what can we do in terms of creative thinking for addressing climate and addressing biodiversity in a positive way?

CMN: As a tree physiologist, I’m always a big fan of planting trees, as I’ve already said. So I really encourage people to do that when they can. Getting out and enjoying the native environments that we have here, I think is a really good thing to do. So I encourage people to do that and do remember to vote with the election.

GP: I’m perhaps a bit more pessimistic than Cate and Kevin. I don’t think that we are going to engineer our way out of this, and I don’t think reliance on market norms is going to help us resolve this. And at heart, I’m not even convinced these are science questions that we deeply need to grapple with. I think we have to address the fact that we live well beyond our means.

GP: And we’ve talked about budgets for the last hour and as a species, we’re well outside our budget. There was a paper in Science last week suggesting we’re outside six of the safe operating spaces for humanity now. I think we really, all individually, speaking as someone who’s a middle-aged white man with immense privilege, look at our consumptive behaviors, how we engage with the world, how we engage with the people around us.

GP: And you can do that through small things. You could become vegetarian, you could eat less meat, you could try and get an electric vehicle. But we also need to make those things accessible and just in the way they’re provisioned. So, I’m a firm believer at the risk of sounding trite, that the individual things we all choose to do, do matter, but we have to choose to do them.

MA: Well, thank you so much, all three of you, for joining us here on Sustain. And I really appreciate your wisdom and your time. And that’s it for today’s programme. Thank you to all of our guests and most of all to you for listening. We’ll see you next time.