HANNAH RITCHIE: My name is Hannah Ritchie. I'm a researcher at the University of Oxford, and I'm deputy editor of "Our World in Data". I recently published a book called "Not the End of the World: How We Can Be the First Generation to Build a Sustainable Planet."

- [Interviewer] Tackling Our Biggest Environmental Problems with Hannah Ritchie. Part One, Climate Change. Has your thinking on climate change evolved over time?

- I think many people today feel doomed about the state of the planet. They see climate change and all the other environmental problems evolving, and they think these problems are insurmountable and we just won't be able to solve them. Now, I've previously been in the same position. Go back a decade or so, I definitely would've called myself a doomer. I just couldn't see how I would possibly be able to tackle these problems. But actually, by stepping back to look at the data and looking at how the world has changed over centuries, I feel slightly differently about this now. It's not that I don't think these problems are big or that they're urgent, but I can start to see that these problems are solvable. You can actually find examples of really big environmental problems that we've already solved. Like, when did you last hear about the ozone layer? Hardly ever because we've actually solved that problem. The same applies to acid rain, another big problem that was front page news a couple of decades ago, but we just don't hear about anymore. We can also see the massive human progress that we've made over the last few centuries. So it's not like humans aren't capable of solving problems. We are, and you can only see that when you really switch off from the news and step back to look at the data. You can see that while we face really, really big and urgent problems, we are developing the solutions and these challenges are solvable.

- [Interviewer] What is driving climate change today?

- So there's a really long list of arguments that climate change deniers would use to debunk that humans are driving climate change or there's any climate change at all. I think some of the key ones that they would use is that the climate has always changed and actually the world has been much warmer previously. And of course, there's truth to this. The world has gone through various cycles in and out of glacial periods and interglacial periods. I think what's really key about this is that these large changes over time have been driven by natural cycles such as cycles of the sun. The changes that we're seeing today are not caused by that, and there's various streams of evidence that we can point to to suggest that we know that this is not the case. So the the main driver of climate change today are human emissions of greenhouse gases. Now, these come from a range of sources. I like to split it up into kind of two main categories. First, we have energy and industry. So that's powering our homes, heating our homes, moving around, so transport on the roads or in the skies, and also industry, producing cement or steel or the stuff that we buy every day. That accounts for around three quarters of our greenhouse gas emissions. There's another quarter which comes from our food and agricultural systems. So this is stuff like deforestation, using fertilizers, cows burping. Our food emissions tend to contribute around a quarter of the world's greenhouse gas emissions. So if we look at carbon emissions over the last 50 years or so, we saw really rapid growth during the 1980s, 1990s, and early 2000s. If we look at where we are over the last five to 10 years, we have seen a significant slowdown in the growth of CO2 emissions globally. Over the last five years or so, we've kind of tended to see a kind of oscillating peak where we're not sure we're exactly at the peak, but our emissions are growing much, much slower than they were in the past, and we hope that we will reach a peak and start to decline emissions in the next few years. Now when we look at global emissions per person or per capita, what we see is that we actually peaked around 10 years ago in 2012. Now since then, emissions haven't fallen dramatically. They've fallen a little bit, but it looks like we have actually passed the peak of global per capita emissions. So over the last few decades, many rich countries have reduced their carbon emissions. Now, the argument that people always put forward is they've only managed to achieve this because they've been offshoring emissions to other countries. So rather than the UK or the US producing stuff, they've just got China or India or other countries to produce our stuff for us. So these emissions reductions are kind of faking it because we've just offset them and offshored them to other countries. Now, we can adjust for this in the data. We can calculate what we call consumption-based emissions, which try to adjust for the carbon that we import from other countries. Now when we do this calculation, we can see that most rich countries are net importers of emissions. We are offshoring some of our emissions, but even when we adjust for this, we have seen a significant decline over the last few decades. So offshoring is a bit of this reduction story, but it's not the entire story.

- [Interviewer] Are the goals set by the Paris Agreement still achievable?

- So in the Paris Agreement, the world agreed to try to keep global temperatures well below two degrees of warming compared to pre-industrial temperatures and as far as possible to limit this warming to 1.5 degrees. For me personally, I tend to think that the 1.5 degree target is no longer feasible. I think the scale and the pace of emissions reductions that we would need is probably out of reach at this point. I would love to see it happen and we should pursue this as much as possible, but I think it's gonna be very, very difficult and I don't see us achieving that target. But I think the key point is that doesn't mean game over. That doesn't mean we are flipped into a world and to a point of no return. For every increment of warming, the risk of climate change increase. So that means that we need to fight for 1.6 and 1.7 and 1.8 because it reduces the risks and impacts of climate change. Now, we still think it's feasible to keep temperatures below two degrees. I think it'll be incredibly ambitious and incredibly difficult. But actually, if you look at the targets that each country has on the table, if they were to achieve them, we would actually possibly sneak just under two degrees. So I think it's really difficult, but I think it's still achievable that we limit temperatures if not below two degrees, very, very close to it.

- [Interviewer] How do we solve climate change?

- So I think there's four key areas that we need to target in order to solve climate change, energy, transport, food, and construction. So what's really key to transforming our energy system is that we need to move away from fossil fuels to low carbon sources of energy. Now these include renewables such as solar, wind, hydropower, geothermal, but it also includes nuclear energy. These are our low carbon sources of energy. Now we need to do this in various ways. We need to decarbonize our electricity grid, which is basically replacing coal and gas with these low carbon energy sources. What we also need to do is try to shift as much of our energy towards electricity as possible. We know how to decarbonize our electricity grids, but there's other aspects of energy which are much, much harder, such as industry or transport. What we need to do is then try to shift those towards electricity so they can then decarbonize by deploying renewables and nuclear. What's really, really key about this transition is that the alternatives to fossil fuels need to be cost competitive. We will not make progress on this problem if solar, wind, or nuclear are more expensive than coal or gas because countries just will not make that transition. But there's some good news here. If you go back a decade, for example, solar and wind were among the most expensive energy sources that we had. But over the last decade or so, we've seen really rapid reductions in their costs such that they're now cost competitive or even cheaper than coal or gas. That means that making this transition is not just about economic gains in the long term when we factor in the impacts of climate change, it's already cost competitive and economic to make this transition today.

- [Interviewer] What impact does renewable energy have on land use?

- So many people are quite rightly concerned about the potential implications for land use by moving to renewables. They picture, you know, fields full and full solar panels and all of our landscapes transformed into wind farms. But actually when you run the numbers, they tell a slightly different story. When we look at how much solar we would need to to meet demand for the world's electricity today, we could actually produce that on less than 1% of the world's land. For wind, obviously the amount of land we would need would be more than this. You're probably talking between 10 and 15%. I think what's important to highlight about wind is not necessarily about the direct impact on land use that's the problem, is more the visual aspect. Actually the direct impact of actually putting a wind turbine in the ground is very, very small. Much, much less than 1% of the world's land. You can actually use the land between wind turbines for uses such as farming. The farmer gets additional profit from the wind farm and can continue to farm between the different wind turbines. So the direct impact on land use is actually very, very small there. You just have the visual impact of stuff that you can see in your eye line. I think it's important to also highlight how this contrasts with other stuff that we use land for. We often imagine that our impact on land use in the world is very much about urban landscapes and roads and infrastructure, but actually this makes up less than 1% of the world's land use. In contrast, we use almost half of the world's habitable land for farming. Our biggest footprint in terms of land use is farming, it's not energy infrastructure and it's not urban infrastructure. Now, if you wanted to spare as much of the world's land as possible, your best option would be nuclear. The land footprint of nuclear is incredibly, incredibly small. It's by far the lowest of all of our energy technologies. You could feasibly power the world on probably less than 0.1% of the world's land. So if it's land use that you're most concerned about, your best option is nuclear power.

- [Interviewer] Is mineral extraction required to increase renewable energy?

- So as we move to a decarbonized energy system, we will need more of different minerals. We need less fossil fuels, but we'll need more lithium and copper and silver and a range of other minerals to build electric vehicles, to build solar panels, and to build wind turbines. Now, many people are concerned that we might not have enough of these minerals, but actually when you look at the data, it's very clear that we do. We can look at scenarios of how much of different minerals we would need to decarbonize our energy system. And for most minerals, these tend to be lower than what we know we have in reserves. That's the stuff that we know we have underground and can feasibly dig up. I think what's also key to highlight there is that these numbers are never static. We tend to find new resources and new reserves that we can use. So actually our known reserves tend to increase over time, not decrease. I think the other concern that people have is the sheer environmental impact of all the stuff that we'll have to mine out of the earth and we will need to mine a lot. If you look at scenarios, we probably need to mine 10 to hundreds of millions of tons of different minerals to build all the infrastructure that we need. Now at first glance, that sounds really alarming. 10 to hundreds of millions of tons. But contrast that with what we're currently doing with fossil fuels, where we're digging out 15 billion tons every single year. What we're doing when we're building a low carbon energy system is we'll initially have an extraction period, which will be orders of magnitude less than annual use of fossil fuels. But we'll also move is to a more circular economy of these minerals. We won't have to dig them out year after year after year. We can start to recycle them and rebuild infrastructure that we had previously. You just cannot do that with fossil fuels. You have to keep digging.

- [Interviewer] How do we transform our transportation systems?

- So transport accounts for around a fifth of our CO2 emissions. Now most of that comes from cars and trucks on the roads. So around three quarters comes from road transport and the rest comes from rail, which is very, very small, shipping, which is quite significant, and also aviation. I think the most obvious way to reduce our transport emissions is just to drive less, to walk or to cycle or to use public transport. Now that requires us to rethink the way we design cities and design communities, but it does have additional benefits. If we design really productive cities which have good public transport networks, we don't just see a dramatic reduction in emissions. We also see health benefits, we see improved communities, and more livable cities for us to live in. But I think we should also acknowledge that we won't be able to get rid of cars completely, but we can start to decarbonize cars as well. You know, the question I always get is, is an electric vehicle actually better than a petrol or diesel car? And the answer is yes. If you just take the cars when you initially manufacture them, the electric car will actually have higher embedded emissions than a petrol or diesel car. That's because it does take more energy to produce the battery. But once you start driving the car, this very, very quickly pays off. So in the UK, for example, after just two years of driving, the average driver will have paid off the carbon debt of manufacturing the car in the first place. And from then on, you just get really rapid reductions in the CO2 emissions compared to a petrol or diesel car. So over the lifetime of the car, you're probably talking about a reduction of around half to two thirds compared to a petrol or diesel car. But what's really key about this is that your electric car will get cleaner and cleaner over time. That's because we'll also be decarbonizing our electricity systems as we move over the next decade. That means your electric car 10 years from now will emit much less CO2 than it does today 'cause hopefully that will be powered by solar and wind rather than coal or gas from the electricity grid. What's really, really key about this transition from petrol and diesel to electric cars is that they need to be cost competitive, right? People will not choose an electric vehicle if it's much, much more expensive than a petrol or diesel car. And what's been really, really fundamental here is the really rapid reductions in cost we've seen for batteries. So most cars today are powered by lithium iron batteries and actually since the 1990s, we've seen really rapid reductions in the cost. We've seen reductions of more than 98%. So if you look at the standard battery that you might find in a Tesla car today, if you go back to 1991, it might have cost between half a million and a million dollars for the battery alone. Today, that same battery probably costs between 10 and $15,000. Much more economic and very much in line with the price of a car that you might see on the market today. So many people might think that this transition is impossible because we've just keep seeing more and more and more petrol cars on the road. But actually the world has already passed the peak of global sales of petrol and diesel cars. They peaked in 2017 and they're now falling. All of the growth in the car sector is now coming from electric vehicles and we see this progressing at a much, much faster rate. Year on year, we see really rapid increases in the uptake of electric vehicles.

- [Interviewer] What can we do to transform construction?

- So the final source of emissions is construction and manufacturing stuff. Now, I guess there's a couple of components to where these emissions come from. One is just using energy to produce the stuff and we know how to decarbonize that. But for some key materials there are another source of emissions, more direct emissions. Take the example of cement. So how we produce cement is that we take limestone, which is calcium carbonate. We turn it up at very, very high temperatures, probably around 900 degrees Celsius. And what we get out of that process is calcium oxide, which is the molecule we then use in cement. But as a byproduct, we also produce CO2. Now that CO2 is simply emitted into the atmosphere and it contributes to global warming. So what we really need to do is get rid of that CO2 byproduct from this process. Now there are a couple of key ways that we can reduce emissions from cement. One is actually to just use less cement. Now that doesn't necessarily mean using less building materials, but we can use a lower grade or a lower composition of cement in our final product that we then use to produce buildings. I think the second key one that we can do is we can capture that carbon dioxide at the end of the process. We can then either actually put it back into the cement where it can potentially make it stronger or we can capture it and store it safely underground so it doesn't escape into the atmosphere. This is typically what we call carbon capture and storage. The final way, which some companies are innovating on, is not using limestone as the source rock in the first place. They're experimenting with sources such as calcium silicate, which will give you the same cement, the same product that we need. But because there's no carbon in there, you won't get the CO2 at the end of the chain. So we have a couple of key solutions which might come online in the next decade in order to decarbonize cement. I think what's gonna be really, really critical is that these can be cost competitive with cement that we have today. Although we might be able to do this feasibly from a technical perspective currently, what's really, really key is that we drive the cost down such that there's no more expensive than what we already have.

- [Interviewer] Who will be hit hardest by climate change?

- So the people that will be hit hardest by a rising global temperatures will typically be those that are poorest in the world. There are a couple of reasons for this. We expect that temperatures will probably hit the tropics and the subtropics hardest, zones that are already quite close to a very high temperature threshold. Increased warming obviously pushes them much, much further and possibly over the temperature threshold which is habitable and comfortable for humans to live in. I think there's another dimension to this, which is that the poorest tend to be less able to adapt to these changes. Adapting to warming temperatures may be okay if you can turn on the air conditioning, but if you can't afford air conditioning or can't afford other ways to adapt, then you're just exposed to these elements. So it will primarily be the poorest typically in the tropics and sub-tropics, which will be much harder hit than those of us typically in the global north. I think what's really key to highlight about climate change is the really large inequalities in the world, not only on where the impacts of climate change will hit, but also who's contributing most to the problem. When we look at per capita emissions across the world, we see really, really large inequalities. These differences between countries can be as much as 10 to 50 times as much emissions per person from countries such as the US, which tends to be a pretty high emitter, to many countries in Africa where most people actually don't burn very many fossil fuels at all.

- How would you define sustainability?

- So as an environmentalist, I previously would've defined sustainability as having a low environmental impact to protect future generations and other species. This is a crucial part of this definition, but I actually think it's only one half of it. I think there's another half, which is that we also need and want to provide a good life for everyone on earth today. So my kind of definition of sustainability, which is kind of in line with the definition of sustainable development, is providing a good life for eight or nine or 10 billion people that we'll have on the planet while also reducing our environmental impact to protect future generations and other species. So I actually think one of the key things we need to do to adapt to the inevitable climate changes that we'll see is to pull people out of poverty, and that's a very, very generic solution, but I think it's very, very critical if we're to protect some of the poorest in the world. When you increase your income, you increase access to energy, you increase access to resilient infrastructure and resilient housing, and you also increase resilience to spikes in energy prices or spikes in food prices. So this is really, really fundamental. We need to, as much as possible, to lift people out of poverty so they become more resilient to the climate changes that we'll inevitably see. Another key thing that we need to do, and a big concern for me is the impact on our food systems. As climate change progresses, as temperature rises, we will expect that we'll see a reduction in yields across the world. Now, it's not that we can't adapt to that. There are things we can do to mitigate some of those impacts. We can produce more drought or temperature-resistant crops, for example, or produce crops that are more resistant to diseases and pests that we might see at higher temperatures. We can also improve access to irrigation, for example, such that when there is a drought or when there are water shortages, farmers still have access to the vital water they need to keep the crops going.

- [Interviewer] What can individuals do to progress sustainably?

- So I think this generation is actually in a really, really unique position. I think we have a really unique opportunity ahead of us. I think if you look at the evolution of human history, human progress was often very much in conflict with environmental impact. The more that humans progressed, the more the environment degraded. I think we're in this really unique position where I think these two things are no longer in conflict. We can progress humanity, we can provide a better life for everyone today while also reducing our environmental footprint at the same time. This is a really unique position to be in. No generation has been in this position before, and we can do that because we have technologies that decouple our human well-being with our environmental impact. We have institutions that can put policies around this to drive this further. And we have more intelligent, educated humans than ever who are really, really serious about working on these problems. But I think it's important that we can see that there's an opportunity there and it's really up for us to grab it and to make it happen. So you might be asking what can you do in order to reduce the impacts of climate change? I think many of us focus on what we'd call our individual carbon footprint. So that's trying to reduce the emissions that we have from the behaviors and products that we consume. That's a very, very valid goal. There are a range of things you can do here. For me, what's really key is to focus on the really big stuff. We will not solve this problem by focusing on plastic straws and plastic bags. We need to focus on maybe the five big things that contribute to emissions. What you eat. So primarily eating less meat and less dairy would make a big impact. Wasting less food, thinking about how you transport. So if you have a car, switching to an electric car or walking and cycling. Flying is obviously a big contributor to your individual carbon footprint. And stuff in your home, like how you heat your home or if you put a solar panel on the roof. These are the really big things that will reduce your individual carbon footprint. I think people see these individual changes as very, very separate from the systemic changes that we need, but I actually don't think the division here is as clear as people assume. When you are working towards a low carbon lifestyle, while you are buying low carbon products, you're both signaling to the government that this is what you want. When you're buying electric car, you're signaling we need more charging stations, we should be putting more policies in place to increase electrification of transport. But you're also signaling to the market that this is where people are shifted. So manufacturers and innovators start to move from petro and diesel to electric cars and push forward innovations in this area. So I think when you individually are moving to these lower carbon products, you're also pushing government and the market and innovation in that direction as well. I like to frame myself as an urgent optimist. Now this is different from a complacent optimist or a stupid optimist, which is someone that just assumes that the future will be better than it is today and no, it won't. It will only be better if we make it better, but that's where the urgent optimist comes in. I think an urgent optimist sees that we can build a better future. We do have solutions and if we implement them, the world can be a better place, but is really serious about how to drive that action forward.

- [Interviewer] Part Two, Food Production. What impact does food production have on our planet?

- I think there are very, very few environmental problems that food doesn't touch on. In fact, I think there are very, very few environmental problems that food doesn't sit at the heart of. So around a quarter of our global emissions come from food and that comes from various sources. One of the key ones is land use change. So expanding agricultural land causing deforestation and our land use changes emits CO2 into the atmosphere. I think some of the other key ones are emissions on the farm and here some of these key emissions are actually not carbon dioxide, but other greenhouse gases such as methane and nitrous oxide. So one of the key emitters, for example, is what we call enteric fermentation from cows, which is basically just cows burping, but they burp methane, which is really powerful greenhouse gas. There are other contributors to greenhouse gas emissions from food such as applying fertilizer. We apply nitrogen fertilizer to the soil. We get nitrogen oxide emissions, which is a really powerful greenhouse gas. You also get the same from manure, which also emits these nitrogen greenhouse gases. Now what that means is that we look at projections of our emissions from food systems out towards the end of the century. Even if we were to stop burning fossil fuels today, those emissions from our food systems would blow us right past our target of limiting warming to 1.5 degrees Celsius and also use up nearly all of our carbon budget for keeping temperatures below two degrees. In other words, if we do not transform our food systems, we won't be able to limit climate change to our international targets. Our food systems are the leading driver of deforestation, the leading driver of biodiversity loss, the leading driver of fresh water use, and the leading driver of water pollution. If we don't address these issues, we'll see the continued acceleration and loss of the world's species and ecosystems. We put severe pressure on our fresh water systems leading to fresh water stress and scarcity, and we pollute our water systems disrupting ecosystems and making them less amenable to life.

- [Interviewer] How do we build a more sustainable food system?

- I think we look at the wide range and magnitude of the environmental impacts of our food system. I'd say we are already eating ourselves into unsustainability. Our food system today is unsustainable, and if we don't change the way we produce our food and the way we eat our food, we will make this problem worse and worse. So when we look at our food system, we have two key goals. The first is that we want to be able to provide everyone with a good sufficient and nutritious diet. The second problem that we also want to solve is to do this with a very, very low environmental impact. So the big overarching problem of our food system is how do you feed eight, nine, 10 billion people with a very, very low environmental impact? So the average person in the world tends to need around two and a half thousand kilocalories per day. Now that varies depending on the type of person, their size, their activity levels, but let's say around two and a half thousand kilocalories per person per day. Now you might think we just produce about enough to feed everyone. In reality, we actually produce around double that amount. The actual crops coming out of the ground is probably equivalent to around 5,000 kilocalories per person per day. Now you might ask, how do we go from 5,000 to only two and half thousand that actually goes into people's mouths? And there are a couple of really big losses that we have in the system from crop production to actual food consumption. I think there are three really big things that we need to do in order to build a more sustainable food system. The first one is to invest in more productive agriculture. We need to be able to produce more food using less land. The second big thing is changing our diets and changing the way we eat. That typically means moving away from meat and dairy, which can include moving to more meat substitute products or dairy alternatives. The final one is simply wasting less food, and that is moving away from consumer waste, stuff we just throw in the bin, but we also have food losses along the supply chain. So these are losses that are unintentional, but food that just rots or goes off because we don't have the storage or the transportation or refrigeration we need in order to get it from the farm to the consumer before it goes off. This type of problem a colleague once explained to me is just a Tupperware problem. It's a problem of, for example, just not having a plastic crate to transport crops from the field to the market. So in some sense, this is good news. This is a very, very solvable and tractable problem. We could not only reduce the environmental impacts of these food losses, but it also means that farmers who ultimately have planted these crops and get them out of the ground, have much, much more to sell at the market and can increase their incomes.

- [Interviewer] How do we increase global crop yields?

- The first thing we need to do is increase crop yields across the world. It's actually one area we've already made a lot of progress. Over the last 50 years in many countries yields have doubled, tripled, in some cases, quadrupled. That means we can produce much, much more food using less and less land, Going forward, that will also be a really key solution. Our key here is to use as little land as possible in order to produce the food that we need. Crop yield will be a really, really key solution to this. Now we know that we can further increase crop yields. We know this because researchers can estimate what they say is the attainable yield. Now the attainable yield is the yield that you could get using best practices and best technologies that we already have today. If you compare that to the yields that farmers are currently getting, there's often a really, really big gap. That means that by increasing access to technologies such as improved seeds, fertilizers, pesticides, and irrigation, farmers can close that gap that exists today. In some regions, this gap is really, really wide. Take Africa, for example, where wild crop yields have increased over the last 50 years. They're much, much lower than the rest of the world and it has started to fall behind. Now what's really key about this investment, it doesn't just improve environmental benefits, but often also provides benefits to the farmer. A farmer will get higher yields and higher income. That's really, really key for some of the lowest income farmers in the world that are living just at or below the international poverty line. They can produce more food, they can get a higher income and move out of poverty. It'll obviously be really key also for regions where we'll see high population growth, not only will farmers get higher income and we'll reduce the environmental impact, we'll also be able to feed more people at the same time.

- [Interviewer] Are we reaching a point of no return for harvesting?

- So this is really common statistic which has kind of become a zombie statistic that the world only has 60 harvests left. Now, there are many phones onto this. Some have said it's a hundred, some have said it's 30, but it tends to be this statistic that hits the headlines and says, "Because of soil degradation, we only have around 60 harvest left in the world." Now this statistic is false, and if you were to ask any soil scientist, they would probably laugh at this claim, not because soil degradation isn't happening or isn't a serious problem, but the notion that all of the world's soils would suddenly stop working exactly the same time is nonsense. The world's soils are so heterogeneous, some are degrading at really rapid rate, some are stable, actually some are rebuilding. So you need to look at this at a very localized or regional level, and you cannot throw out statistics that the world only has 60 harvests left because the world's soils are so diverse and moving in such different directions.

- [Interviewer] How do we address soil degradation?

- So soil degradation is a very, very serious problem and one we need to tackle in our food system. There are a couple of ways that we can start to restore the health of our soils. Some key ones is a low or no-till effect when rather than digging up the soil over and over in a really intense way. You use very low or no tillage in order to keep soil carbon where it is. Some other key ones to restore soil carbon is stuff like we call cover crops. So between different harvests, planting crops that you might not need but are there to keep the carbon in the soil and to keep it in a really, really healthy way.

- [Interviewer] Will land usage increase with population growth?

- So I think that people assume because we've got a growing population that we'll just see us using more and more and more agricultural land year on year. We actually think that we might have already passed the peak of agricultural land. So statistics from the UN Food and Agricultural Organization actually think we reached peak agricultural land a few decades ago around the year 2000. What we've seen since then is a decline in the amount of land we're using for grazing primarily in arid or temperate regions. Whilst we've also seen an increase in crop lands. So while there's some good news there, we know we can produce food in a much more efficient way using much, much less land, we still do face significant problems. We're still seeing the expansion of grazing land, especially in the tropics, that comes at the cost of deforestation such as the Amazon rainforest. We're also seeing continued growth of croplands, which again is bleeding into forests and bleeding into wild habitats. So while we might have already passed peak agricultural land, we still face really, really serious issues in terms of our land use expansion.

- [Interviewer] Does eating local reduce your carbon footprint?

- I think one of the biggest misconceptions I hear is that the best way to reduce the carbon footprint of your diet is to eat local. Now, the rationale for this makes sense. We know that moving stuff around the world, whether in trucks or ships or planes, emits CO2, therefore, you'd assume that the further the food has to reach you, obviously the higher emissions. I think what's really key to highlight here is that most of the emissions from food do not come from transport or food miles. Globally, transport is only around 5% of food system emissions. Most of the emissions come from deforestation or land use and emissions on the farm. So that's stuff like the use of fertilizers, application of manure, or the burping of cows. Cows tend to burp methane, which is a really powerful greenhouse gas. So actually most of the emissions of our food come from the type of food we're eating and how it's produced. And actually the food miles is a really, really small component. Now, what that means is that the classic argument that my local beef is lower carbon than your soy shipped in from South America is just not true. When you step back to look at the data because the transport emissions are so small, it actually doesn't matter that it's been shipped across the ocean. It's the fact that the beef has a much, much higher carbon footprint than the soy that makes all the difference.

- [Interviewer] Is organic food better for the environment?

- I think another big misconception is that eating organic is automatically better for the environment than eating from conventional agriculture. Now, there are some metrics for which organic might be better for the environment. For example, if you're looking at local biodiversity impacts on the farm itself, organic methods might be better than conventional methods that use synthetic fertilizers or synthetic pesticides. But this doesn't apply to all metrics, which really the key about organic agriculture is that you tend to get slightly lower yields. Now what that means is that to produce the same amount of food, you'll typically need more land. Now, of course, land use in itself is a big problem, but it also can result in deforestation or other wild habitat changes and can also result in higher carbon emissions. So when you compare organic and conventional agriculture on greenhouse gas emissions, there's actually usually no clear winner. They tend to be around the same, or even for some products, conventional agriculture can have a lower carbon footprint.

- [Interviewer] Is vertical farming a viable solution?

- Now, one solution that tends to get a lot of attention and to some extent I'm a little bit excited about, but I don't think is a feasible technology today is vertical farming. Now, vertical farming takes crops from out in the field and brings them indoors. Rather than using sunlight, you use LED lights inside in order to have that photosynthesis process. There are obvious advantages to this. You need much less land, for example. You can also use less fertilizers or less pesticides because the crops aren't exposed to pests or diseases. The big trade off here though is that you're substituting land for energy. Typically, vertical farms need a lot of energy to produce these crops. They've been used most commonly for crops, kind of high price crops such as leafy greens or other vegetables. Even there we've seen many big companies start to go bust in the last few years because of a spike in energy prices. It's just not economically feasible for many of these companies to continue producing. I think the economics gets even worse for cereal crops where actually most of the world's calories come from. Estimates suggest that a loaf bread produced from wheat from vertical farming would cost around $18. Now in the future, LED lighting and other energy systems might get more efficient. So we might start to see that cost fall, but you probably still expect a loaf of bread there would cost at least six times as much as the prices that we pay today. So while I think this is an exciting technology and one that might produce some of our food in the future, I think the economics of this technology just don't work today and won't be able this silver bullet solution that many people think it is.

- [Interviewer] Should we de-modernize our farming methods?

- So I think when people see the unsustainability of our food system today, they think the solution is just to go backwards, right? The problem of our food system today is the modern ways that we produce our food. If we could just rewind the clock and go back to how our ancestors did this, our problems would be solved. Unfortunately, this is just not true. The issue there is scale. The food systems that might have worked for tens of millions or hundreds of millions of people just don't scale to a population of eight, nine, or 10 billion people. The solutions of everyone lives on their farm, has their own plot of land, produces free organic agriculture with no inputs, just doesn't scale when you need to feed 8 billion people. That's why we cannot go backwards to the ways that we used to do farming and food production. We need to find a way of building solutions that take us forward, that can feed billions of people, but in a much more sustainable way.

- [Interviewer] How do dietary changes impact our environment?

- The second big thing we need to do is to change our diets. I think we need to be really, really careful when we're talking about dietary change and environmental impacts of food that we're not preaching to people or telling them what they should and shouldn't eat. It is none of my business to tell you what you should eat. I think what's really, really painful for me is that when people have really good intentions, they want to reduce the environmental footprint of their diet. They're just working on poor information. So what I try to do is put out good information such as those that do want to make this change and want to make a difference have good information to make better decisions. Now here the top recommendation is to reduce the amount of meat and dairy that you're eating. Now, the reason for this is if you look at the environmental footprint, now here we can think about carbon footprint, but it also applies to land, to water, water pollution, and biodiversity loss. If you rank foods in terms of their impact, at the top you tend to see a cluster of animal-based products, and at the bottom, you tend to see plant-based foods. Most plant-based foods have a lower impact than meat and dairy. Now here the differences between different food products are really, really stark. For example, if you look at the carbon emissions per hundred grams of protein of plant-based proteins, they can be 10 to 50 times less the impact of really big emitters like beef or lamb. Now, it's important to think about not just the total amount of meat that we're eating, but also the types of meat. This is because the carbon footprint of different meat products is also very, very different. The bigger the animal, typically the higher the carbon footprint. So you tend to see beef is the worse emitter followed by lamb, then pig, then chicken, then fish. So one solution is to eat less meat overall. Another solution is to also substitute the type of meat that you're eating. So for example, substituting beef for chicken would massively reduce your carbon footprint.

- [Interviewer] Is meat an efficient source of nutrition?

- So we have this metric that we call calorie efficiency, and that basically tells us for every 100 calories of crops or feed you feed an animal, a farm animal such as a cow or a pig or a chicken, how many calories do you get in return in the form of meat? What we see when we look at this data is that the calorie efficiency of all animals is actually very, very low. It tends to be lowest for the biggest animals. So for a cow, for example, for every 100 calories that you feed it, you typically get around two calories out in terms of meat. So that means 98% of those calories are lost just keeping the animal alive. You don't actually get that out in the form of meat. For lamb, it's maybe around four. So 100 calories in, four calories out. For pigs, it's around nine. So 100 in, nine out. And for chicken, which is typically the smallest of the animals, is a little bit better. You give 100 calories in, you get 13 calories out. But even for our most efficient livestock and efficient animals, you can see that nearly all of the calories that we feed it is completely lost in that conversion. And people will often say, "Okay, but we mostly meat for protein, not calories. So is the protein efficiency much better?" Unfortunately not. It's a little bit better than calories, but for cows, lambs, and pigs, it's still under 90%. So 100 grams of protein in, you'll typically get less than 10 grams of protein out in the form of meat. Chicken is a little bit better, but it's still less than 20 grams of protein out for every 100 grams that you put in.

- [Interviewer] Is it possible to maintain a plant-based diet?

- Now, a really well plant-based diet can meet most people's nutritional needs. I think there's one key vitamin that you just cannot get from plant-based products, and that's a vitamin B12. So if you are on a plant-based diet, you would need to supplement with vitamin B12, which is either in the form of direct supplementation. Actually many products are actually fortified with vitamin B12 already. For most other nutrients, whether they're macronutrients such as protein or fat or micronutrients such as vitamins and minerals, you can typically get the full spectrum on a plant-based diet, but you probably need to be much more conscious of the diversity of foods that you're eating compared to a diet with meat and dairy in it. I think a really, really key innovation and solution we need in this area is better meat substitutes. I think we could hope that people would just switch from a beef burger to tofu or peas or beans, but for me, I think this transition globally is gonna be really, really unrealistic. I think what we need is to generate meat-like products that taste like meat, that have the texture of meat, that have nutrition of meat just without the animal and the environmental product. Now, there are a range of companies and innovators working on this, but I think investing in this much more heavily will really help with this transition away from meat to a more sustainable way of eating.

- [Interviewer] Does everyone need to go vegan?

- I think when people come to this issue and they tend to see the stats on how big the carbon footprint of meat and dairy is compared to plant-based products, they have the impression that the only way out of this is for us to all go 100% vegan tomorrow, and I don't think this is realistic, and I also don't think this is necessary. For many people, the transition towards veganism or a completely plant-based diet seems overwhelming and daunting, and this is not the message. I think what's really key is that we could all make a difference by small changes. Actually, if everyone in the world were to eat 10% less meat or 20% less meat, we'd actually have a bigger impact than a few percentage points of the population going completely vegan. So for many people, this is not about doing a full transition of their diet, it's about taking incremental steps, maybe first by stopping eating meat on a given day or reducing it at a given meal and slowly working towards a more plant-based diet over time.

- [Interviewer] What could the future look like if we make these changes?

- I think it's really important to highlight that we would produce more than enough food for everyone. Nearly one in 10 people in the world do not get enough calories to eat. This is obviously an unacceptable position to be in, but we do have the solutions we need to solve this. We do produce enough food for everyone, and we could produce much, much more if close yield gaps across the world and change the diets and the way we eat. Another key factor to take into account is that we've also faced changes in the climate, and in some regions, this might make farming more difficult. So we need to be prepared for this. We need to factor in that we need to not only make up this deficit for the one in 10 people today, we might also have additional mouths to feed over the next few decades. We'll also have to contend with the impact of a changing climate on our agricultural systems. Now, these obviously are massive problems, but we do have the solutions we need to solve them. We know that we can increase crop yields if farmers have access to the tools and practices that we need. We can produce really efficient meat substitute products, which mean that we can release a lot of land from food production and also release a lot of crops that we're currently feeding animals and put it more directly into human mouths. So if we were to implement all of these solutions, if you look at where the world might be in 2060, we'd very comfortably be able to feed a population of 10 billion people. We wouldn't have anyone that are undernourished or malnourished. Everyone had access to enough calories, enough protein, and a diverse diet. But we'd also produce this food with a much, much lower environmental impact. We could massively reduce the amount of land that we use for farming. For example, if the world was to go completely plant-based, which it might not, but even if it did, you could reduce agricultural land use by 75%. We'd use only a fraction of the land that we currently use for farming, which would mean we'd free up lots of land for the restoration of wild habitats and forests. We would end deforestation because food and agricultural expansion is the leading driver of deforestation and biodiversity loss today. We would also massively reduce the pressure on fresh water resources and fresh water pollution. Again, our food systems are the leading driver of fresh water withdrawals and also fresh water pollution. In 2060, we could see a world where 10 billion people are fed nutritiously with a fraction of the environmental impact that our current food system has. What's also really key here is a more productive agricultural system would massively increase the incomes of many farmers around the world. Many of the world's poorest are small holder farmers where most of the family works on the farm and gets very, very little in return. They're often just at the international poverty line of earning a few dollars a day or might even be below it. With more productive agriculture, fewer and fewer people in the family would have to work on the farm, so kids could go to school, to university to move on to different careers, and the farmers still working on the farm would have a much higher income and a much higher standard of living. So don't think we should underestimate the scale of this challenge. I think we should be aware that we do have the solutions to solve this.

- [Interviewer] Part Three, The Plastic Problem. Why is plastic so prevalent?

- I think plastic has completely transformed the world. I think you look before plastic, the materials we had were wood or textiles or metals or other heavy materials. I think plastic has had such a transformative impact because there's really, really almost magic-like properties. It's light, it's flexible. You can almost mold it into anything you want. It's waterproof, it's sterile, and most importantly, it's cheap. Over the last few decades, global plastic production has exploded. In the year 2000, we were producing around 200 million tons. By 2010, we were producing 300 million tons, and by 2019, we were producing 460 million tons. Actually, if you add up the cumulative amount of plastics that were produced since 1950, it comes to around 10 billion tons. That's more than one ton for every person alive on earth today. I think these range of properties have been really, really key to its success, such that over, especially over the last 50 years, we've seen almost this explosion in global plastic production. But I think it's also its downfall because it's so flexible and so cheap, it's so, so easy to produce more and more and more of it. You can almost produce it at very little to no cost, and at the end of the chain, because it's so cheap, there's very, very little incentive to recycle it. It's often costs more in terms of energy or money to recycle plastic than to just produce more of it in the first place. So I think the magical properties of plastic have transformed the world, one in a very positive way and also in a very negative way in terms of the environmental impacts.

- [Interviewer] Why is plastic waste a problem?

- When it comes to plastics, there are two key problems. One is the leakage of plastics into rivers and oceans and the pollutions of oceans with plastic waste. This is a very tractable problem. This is a problem that we know how to solve and could do it. I think there's a second problem, and that problem is microplastics. Now, these are very, very small plastic particles that tend to result from the breakdown of larger plastic particles. Now, almost every week now, we see a study coming out telling us the fact that microplastics are everywhere. They're in Antarctica, they're in the water we're drinking, they're in the food that we eat, and this is a really, really key concern for human health. I think it's important to be clear that we don't actually know what the impacts of this on human health are yet. I think this is a really unexplored but important area of research to delve into. I think some of the key issues with microplastics, and especially because of their really small size, they can get into parts of our bodies that other particles, bigger particles can't. For example, they might be able to get into our bloodstream or they may be able to break the blood brain barrier. This is obviously very concerning, but we just don't know what the scale or magnitude of these impacts are yet. I think another potential problem of microplastics is not the particles themselves, but the fact that other pollutants, other external pollutants may be able to bind to them and then bring those pollutants into our body, into our bloodstream, or into our brains. I think it's important to highlight that this is a very under-explored area, so we can't make any definitive statements on what these potential health impacts would be, if any. But I think that's so important because it really matters for how we tackle plastic overall.

- [Interviewer] Where does plastic waste come from?

- I think when we try to work out where plastic waste is coming from, I think we might assume that it's coming from countries where people use the most plastic. So to blow up a big map of plastic use per person across the world, you'd see rich countries produce the most, typically Europe or North America. Per person, we use much, much more plastic than many other countries in the world. The problem is this doesn't necessarily translate into plastic waste that leaks out into the ocean. This is because it matters how you manage this waste. In rich countries, we use a lot of plastic, but we also have good waste management infrastructure, such that most of this goes to closed landfills or recycling centers or incineration centers, and that means it doesn't leak out into the environment. In contrast, in many middle to low income countries, they use much less plastic per person, but a lot of this plastic waste at the end of the chain leaks out into the environment because they don't have good waste management infrastructure. So I think it's important that we separate plastic waste production problem from the plastic waste management problem. Another key problem is the fishing industry. When we look at global plastic waste, most of this actually comes from land. Most of it comes from rivers and then leaks out into the ocean. Here it's a problem of fishermen dumping nets or ropes or other plastic materials that they're using as part of the fishing industry, and in many parts of the ocean where fishing activity is very high, this is actually the leading contributor to plastic waste.

- [Interviewer] What is the Great Pacific Garbage Patch?

- The Great Pacific Garbage Patch, often referred to as the GPGP is this massive vortex of plastic waste in the North Pacific, a couple of hundred miles north of Hawaii. Now in the North Pacific, there is this oceanic gyre, which tends to circulate waters around in a current. What's happened is that plastic has been pulled into that gyre, such that you now have circulating patterns of plastic waste. To give you some context of the size of the Great Pacific Garbage Patch, it extends around 1.6 million square kilometers, which is around three times the size of France. You know, the density of plastics in this gyre is quite low. It's not that you have lots of plastics stuck really, really dense and tightly together, but actually this is quite a problem for gathering that plastic. It might actually be easier if it was lumped really, really close together so you had a much smaller area to gather it. There are estimates that are around 80% of the plastics in that gyre come from fishing activity, so that's stuff like ropes, lines, or net that fishermen are using and chucking overboard. This is not true of plastics overall in the ocean, estimates are almost that it's the opposite. Around 20% of total plastics come from fishing activity and 80%, so most of it, come from land-based sources such as rivers and and coastlines.

- [Interviewer] Should we stop using plastic?

- I think some people's solution to this is, "Oh, we should just stop using plastic completely." I actually think this is not the outcome that we want. While plastic does have significant environmental impacts and we need to tackle the waste problem, I think we should also acknowledge the benefits that plastic brings. Think of food systems, for example, and food waste. While many food products have too much packaging and we could certainly cut back, the plastic is often there for a reason. It increases the shelf life of the product and stops it from becoming food waste, which also has really high environmental impacts. Think about our health systems and the need for sterile needles or COVID masks or plastic gloves that doctors use. It'd be really, really hard to substitute that with really good sterile alternatives. One of the key areas where plastic is used is in transport. So for example, in the manufacturing of cars or trucks or planes, the key fact there is that plastic is a much, much lighter material than aluminum or other metals that you might use instead. By using these lightweight plastics, we can still have the same strength of the car from other components, but they're much, much lighter, which makes them much more efficient and makes them use much, much less energy. It's also the case when we're transporting particular goods. Goods wrapped in plastic or in plastic bottles can be much, much lighter than the same products in glass or other materials. Again, the transport emissions and energy use is proportional to the weight of those particular goods. By using lightweight plastics instead, we actually reduce fuel use and also reduce carbon emissions. Also, think about the building of stuff and construction. If we weren't using plastics, we might need to use glass or more concrete or other metals, which are also really energy intensive to produce and probably also have a much higher carbon footprint. So while there's certainly massive room for cutting back on plastic and the overuse of plastics, I think this catchall solution of we should just stop using plastics, could actually make many of these environmental problems worse, not better.

- [Interviewer] Is recycling a solution to our plastic problem?

- I think some people might see recycling as the silver bullet solution to plastic waste. Not only do they see that we might just eliminate plastic waste completely, but we might be able to stop producing more of it in the first place. Maybe we can just get into this closed loop where we recycle plastics over and over and over again. Unfortunately, this is not the reality. Recycling can help. When you recycle a product, it can be produced into another product. But I think what's really key to highlight here is that you're often recycling it into a lower value product. The plastic waste bottle that you recycle is not then recycled and reused as another plastic waste bottle. It tends to be ground down and used into lower value products like maybe in a floor tile or other compositions of different plastics. That means that ultimately your recycled plastic bottle will ultimately end up in landfill. It'll just be recycled maybe a few times along the way. So recycling really delays the journey to landfill, but it doesn't stop it completely. When we talk about recycling today, what we're mostly talking about is mechanical recycling, so taking a given plastic product, grounding it down, and making it into something else. There are innovations in what we call chemical recycling, which is basically reusing the chemical components of plastics, not just the mechanical ones. Now, this is a much more efficient way of doing recycling and would massively improve both the environmental and energy benefits of doing it. The downside is that it's currently very expensive and just cannot compete with the cheapness that plastic we have on the market today.

- [Interviewer] How do we fix our plastic waste problem?

- I think the really key problem that we're trying to address here is how do we stop plastic waste going into rivers and oceans and other ecosystems. I think what's really, really key for me to signify here is this is not necessarily a plastic production problem. It's more a plastic waste management problem. It's how the plastic is managed at the end of the chain that matters rather than necessarily the total amount of plastic that we're producing. If we produce a lot of plastic and we can keep it in sealed landfills or recycling centers or incinerators, it doesn't actually leak out into the environment to get into rivers and get into the ocean. So when it comes to actually tackling the problem, one component, yes, is to use a bit less plastic. We overuse plastic packaging. We can cut back on that and that will make the problem easier. But I think a really key solution is just investing in waste management. In many countries where they don't have good waste management infrastructure, plastic production has massively increased and plastic use has increased, but at the end of the chain, there aren't sealed landfills or recycling centers to manage it. So often this waste is either dumped or in open landfill, but it can leak out into rivers and into the ocean. Now, I think many people would see this as only a problem for middle and low income countries 'cause ultimately this is often where a lot of the plastic waste leaks out into the ocean because the waste management infrastructure is not there, and while this is a really key issue and this is where most of the investment is needed, I think rich countries shouldn't be let off the hook. I think rich countries can also play a key role in contributing to this. Many of our politicians stand up and make grand claims about how much we want to tackle plastic waste, but then they often put in policies that make very, very little difference at all. They put in policies like banning plastic straws, for example, which has almost no impact on the plastics leaking out into the ocean. If rich countries want to get behind this, one of the key things they can do is also invest in waste management infrastructure in middle to low income countries. I think what's also key is that countries can also export their plastic waste to other countries. That's currently what's happening today. When rich countries are doing this, knowing that other countries do not have the waste management infrastructure to handle it, they're basically dumping that problem on someone else. That should give them even more drive to invest in solutions, not just at home, but for other countries as well. We need a global coordinated effort to tackle this, but the good news is it is tractable problem. Many countries can manage their waste and with enough investment, this can be the case across the world. I think that building up our waste management infrastructure will take time. So there are also some cool technological solutions that could come online and if not stop the problem, it could at least limit it in some regions. There is, for example, a technology called the Interceptor Original, which is where basically we try to catch the plastic at the end of rivers just before they meet the ocean. This is where most of the plastic waste is coming from. If you can put up a barrier such as a float or a gallery net at the edge of the river, at the mouth of it, you can stop the plastic before it leaks out into the ocean and becomes much, much more dispersed. You can then gather that plastic and manage or recycle it properly so that we don't contribute to this plastic waste problem. This is currently a small scale project and it's only in use in a couple of big rivers in the world, but if you could massively expand it while we build waste management infrastructure, you could stop a lot of plastics leaking into the ocean. I think the ocean plastics problem is one of the most tractable environmental problems that we have. We know this because we know that many countries already emit very little plastics into the ocean. They have good waste management infrastructure, they have landfills, They have recycling centers or incineration centers, and very, very little plastic waste that they use ultimately leaks out into the environment. If you were able to do this everywhere, we could bring global plastic pollution to an end. The key barrier here is investment, investment in waste management infrastructure and investment in different projects that are trying to do this at a much smaller scale.

- [Interviewer] What can we as individuals do to prevent plastic waste?

- Now, you might be wondering, what can you do about this? There are obvious very small behavior changes you can make like limiting plastic use, like reducing the amount of single use plastics that you use, but there are also bigger stuff that you can do. One of the key things and one of the key problems is that plastics tend to, once they go out into the ocean, tend to then wash back up on beaches and coastlines. Why not join a group that goes to these coastlines and tries to collect some of this plastic and manage it properly? Another big thing you can do, if you have the money, is to donate to particular projects working on waste management, whether it's the Ocean Cleanup Project or the Interceptor or many other similar projects or to invest in projects that are trying to improve waste management infrastructure across the world.

- [Interviewer] Part Four, Addressing Overpopulation. Is overpopulation an environmental problem?

- I think if you go back in human history, I'm sure the silver bullet of many environmental problems was just there's just too many people. If we had less people, this problem would be solved. But I think this particular overpopulation concern became really prominent in the 1960s and the 1970s. At the time, the big concern of the day was how we could produce enough food for a rapidly growing global population. I think this is really brought to the fore with the publication of the book, "The Population Bomb" by Paul R. Ehrlich in 1968. I think there are many people of this same opinion today who still really strongly argue that the root of our environmental problems is there are just too many people on earth. So some of the really alarming proposals on how to tackle overpopulation, some of them in the book, "The Population Bomb", are, for example, adding sterilants to the water or food supply, offering responsibility prizes for families that chose not to have children, offering lotteries where you only get into the lottery if you are a couple that hasn't had children, ruining financial support for families of a given size, or some of the most morbid, which is this notion of forced or encouraged sterilization, but also the withdrawal of food aid packages. There's often this framing of a triage system where some countries in the world might be redeemable and maybe we should help those countries to feed themselves, but some countries were past this point, they could never be able to feed themselves and therefore, we should withdraw any food aid.

- [Interviewer] What does the overpopulation argument get wrong?

- I think there was two key things that prominence of "The Population Bomb" or this overpopulation argument got wrong. I think the really key one is that they underestimated the demographic transition. I think they assumed that the world population would continue to grow exponentially and it hasn't. While the global population is still growing, in fact, it is growing a much slower rate, it's not growing exponentially. Global population growth rates peaked decades ago and have halved since then. If we look at projections into the future, the UN, for example, expects that global population will peak well before the end of the century and start to decline. The key thing that they underestimated here was the fall in global fertility rates. Now, this is the kind of average number of children that an average women would have. Now globally in 1950, that was around five, so every women would have on average five children. That has since fallen to 2.3 children per women, and this is true across most countries in the world. I think the other key thing the proponents of this underestimated was the massive technological advancements we've seen in agriculture. The issue at the time is that we wondered how we would produce enough food for a growing population, but not only has global population growth slowed, we've also massively increased the amount of food we can produce. Crop yields across the world have doubled, tripled, or quadrupled over the last 50 years, which means that the amount of food we produce per person has actually gone up, not down despite the fact that we have billions of more people on earth. I think a key argument that people often say in terms of climate change, again, is that there's just far too many people, and they'll often point to particular countries where fertility rates are still very high. There are some countries, for example, across Africa where the average number of children per woman is four or five. I think what's really key to highlight here is in these countries where fertility rates are very high, the incomes are low, and per capita, CO2 emissions are also very, very low, extremely low. That means that when you do the maths on this, you could actually add billions of people at those very low incomes. It would have almost no impact on global CO2 emissions.

- [Interviewer] Why is the messaging around overpopulation damaging?

- I think there is this comparison that's often made by people that say that, you know, the problem is overpopulation, and it was true in the book "The Population Bomb" is that humans are often compared to a cancer, a kind of organism that just self propagates and overtakes complete ecosystems and dominates and that we want to get rid of it. I think this is a very damaging comparison to make for humans in the world. I actually think it's a problem for some environmental messaging overall. I think it leans into this anti-human concept, which I think is just not useful in terms of building solutions that move us forward. The problem with this comparison is that with a cancer, there's very few redeemable qualities, right? When you have a cancer, what you want to do is reduce it as much as you can, and if possible, completely eliminate it. This is a problem if this is the comparison we're making with humans. While it's true that we do have environmental impacts and we do have large problems to solve, I think it's a very dire prediction that we don't contribute anything to the world. If your messaging is that the human front of you is a cancer, what you're saying is that you don't want them to be there and you think that they should be removed. If this is gonna be the comparison we make on how to tackle environmental problems, it's a really damaging messaging and just one that won't get us there.