8th March 2023 Transcript
Host: Nick Petrić Howe
Welcome back to the Nature Podcast. This week, how wildfires could destroy the ozone layer
Host: Benjamin Thompson
And how to protect our food systems with digital twins. I'm Benjamin Thompson.
Host: Nick Petrić Howe
And I’m Nick Petrić Howe.
[Jingle]
Host: Nick Petrić Howe
First up on the show, why wildfires may complicate the ozone layers recovery. Ozone is pretty important. These molecules are made up of three oxygen atoms and are found in particularly high concentrations in a thin section of the Earth's atmosphere known as the ozone layer. This thin layer has been pretty crucial to life on the planet, as atmospheric chemist Susan Solomon explains.
Interviewee: Susan Solomon
We'd have absolutely no life on the planet surface if we didn't have an ozone layer. The ozone layer protects us from certain wavelengths of ultraviolet light that nothing else can help us with, so life as we know it at least evolved because we have an ozone layer on this planet, and if we damage it, we'll have all kinds of biological damage, ranging from skin cancer in human beings, cataracts in human beings, to, you know, whatever you can imagine in plants and animals, much of which we probably don't even know, but it's pretty scary to even think about.
Host: Nick Petrić Howe
The ozone layer is so important, it even managed to persuade humanity to work together. When a hole in the layer over Antarctica was discovered back in the 80s, the nations of the world rallied together to ban the chlorofluorocarbons that were to blame in a treaty known as the Montreal Protocol. But that wasn't the end of the story. For the hole to fully close, it still got a bit of a way to go.
Interviewee: Susan Solomon
We've already seen some signs that the Antarctic ozone hole is healing, and we expect that to slowly continue in the future. That doesn't mean you won't see, you know, a few years here and there where there's a big hole, or maybe even almost no hole, but on the whole, we do expect the ozone hole to recover sometime around the 2060s.
Host: Nick Petrić Howe
But there may be a complication to that long road to recovery — wildfires. This week in Nature, Susan and her team are publishing a paper that’s suggesting that wildfires may lead to ozone depletion. They first realized that this could be an issue in the wake of the devastating Australian wildfires in 2020, when the chemistry of the sky above Australia began to be reminiscent of the Antarctic ozone hole.
Interviewee: Susan Solomon
After the Australian fires, I won't say that it looked like Antarctica, but you know it, it certainly didn't look like the planet I was used to, it was as big of a wakeup call, as I've had in my many years of studying this since the ozone hole was discovered.
Host: Nick Petrić Howe
According to the team's models and satellite observations, during this period, ozone was depleted in the region, and the Antarctic hole also got bigger.
Interviewee: Susan Solomon
Basically, the fire canceled out all the hard work that the planet did for the Montreal Protocol.
Host: Nick Petrić Howe
As it seemed that wildfires could lead to pretty substantial ozone loss, the next step for Susan and the team was to work out how. What was it about the fire and the smoke from it that could cause the ozone to disappear? Working this out was tricky because no one really knew much about how smoke particles behave in the high stratosphere where ozone lives. What they did know is that in the past ozone loss has been due to chlorine radicals, which are not a chemistry punk band, but are some very reactive molecules, and these radicals themselves are produced when hydrochloric acid dissolves. One thing that hydrochloric acid is good at dissolving in is super-cold cloud particles. In fact, a big reason that the hole in the ozone layer is over Antarctica is due to just how cold it is. Another thing that dissolves hydrochloric acid, according to the team's analysis, is the compounds found in wildfire smoke.
Interviewee: Susan Solomon
So initially, you get a compound called levoglucosan when you have wildfire smoke, but it then oxidizes, and you end up with things like alcohols and particularly organic acids, actually oxalic acid, interestingly enough, is one of the dominant things observed, and hydrochloric acid is pretty soluble in those, and that's the key thing. Even at room temperature, hydrochloric acid will dissolve in oxidized organic liquids.
Host: Nick Petrić Howe
To see if this was really what was going on in the stratosphere when the wildfires were raging, the team modelled this chemical process and compared it to the satellite observations of what happened during the 2020 wildfires. It seemed to fit pretty well.
Interviewee: Susan Solomon
We were absolutely, I think the British would say, gobsmacked when we saw how amazingly it actually fit every detail of the observations. It’s incredible.
Host: Nick Petrić Howe
Faye McNeill is an atmospheric chemist who's been writing a News and Views article on the new paper. She was impressed by the new work.
Interviewee: Faye McNeill
It's very fascinating, and in part, it's because we don't know that much about what happens in the stratosphere, especially to these smoke particles. It's a little difficult to make observations at that altitude, and it's difficult to simulate that environment in the laboratory, and I think that this result points to some misunderstandings that the field had about what types of chemistry these particles could participate in.
Host: Nick Petrić Howe
In the past, there have been all sorts of assumptions about how smoke like particles would behave in the stratosphere, for example, that they wouldn't be so reactive. This new paper shows the opposite. For Faye though, there are still some open questions.
Interviewee: Faye McNeill
I think there are a lot of questions about the physical state of smoke particles in the stratosphere, what kind of chemistry they could participate in. We don't have direct evidence of these physical and chemical processes happening in the stratosphere yet, so some laboratory studies under well controlled conditions would be great, some field observations, perhaps of a smoke plume in the stratosphere, all these things would offer us a better picture of what's happening and perhaps other chemistry that might be taking place.
Host: Nick Petrić Howe
Susan agrees, and is keen to do further work on this topic. In the end, though, as the climate continues to warm, wildfires are likely to become more frequent. With this new study in mind, it also means that the ozone layer could be increasingly depleted, which gives us all the more reason to tackle climate change.
Interviewee: Susan Solomon
Those of us who study climate, there's a lot of reasons obviously to be concerned about wildfire from the point of view of, you know, the damage to the ecosystem, the damage to property, so, you know, on that scale, you can say this is just one more of the tragedies of what wildfire will do. From a scientific point of view, we need to be making a lot more measurements, we need for people to go in the lab and actually measure the type of stuff that we talked about in the paper and in detail with modern equipment. I'm very excited about the future of this kind of research. I'm not so excited about what it means for the planet.
Host: Nick Petrić Howe
That was Susan Solomon from MIT in the US. You also heard from Faye McNeill from Columbia University, also in the US. For more on this story, check out the show notes for a link to the paper and the News and Views article written by Faye.
Host: Benjamin Thompson
Coming up, how specialized models called digital twins could help mitigate shocks to food systems caused by global crises. Right now though, it's time for the Research Highlights with Dan Fox.
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Dan Fox
Large tropical bats with narrow home ranges are disproportionately likely to be hunted by humans, according to a global analysis of 1,320 species. Researchers found that 19% of the bat species surveyed are hunted, with bats that live on nectar and other plant products the top targets, especially the fruit-eating flying foxes. Other key predictors that a species is likely to be hunted include a habitat that is easily accessible to humans and low incomes among the hunting population. The team found that hunted species are at higher risk of extinction than those that aren't hunted, suggesting unsustainable hunting is itself a driver of population decline. They call for investments in creating economic security and reliable sources of meat from domesticated animals for humans living in key bat habitats. Limiting bat hunting could both protect bats and prevent transmission of infectious diseases from bats to humans. Read that research in full in Biological Conservation.
Researchers investigating the growth of deer antlers have identified the stem cells involved in their rapid development. Every spring, deer lose their antlers, by early autumn, they have a new set. The antlers sprout by about 2.75 centimeters a day, one of the fastest rates of bone growth amongst mammals. Researchers used RNA sequencing to examine almost 75,000 cells from the antlers and nearby tissue of sika deer before, during and after antlers were shed, identifying a family of stem cells that was key to antler renewal. Once one set of antlers has been shed, the cells quickly begin the process of developing into new cartilage and bone. When the team transplanted one subgroup of the cells onto the foreheads of mice, the rodents grew antler-like structures within 45 days. The author suggests that these stem cells could ultimately lead to treatments for bone and cartilage injuries. You can read that research in full in Science.
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Host: Benjamin Thompson
Many of us are in the lucky position that food is plentiful and easily available in places like supermarkets. But the process of getting food from farms to forks is a web of interconnected systems that all have to fit together just so, in order for produce to get from one place to another. But, recent global crises have shown the fragility of this web and future shocks, like those caused by ongoing climate change is set to stress it even more. But, exactly how might these crises affect food security? Well, according to Zia Mehrabi, a data scientist who specializes in food systems, perhaps the best way to answer that question, is to use a specific type of virtual model called a digital twin, and he's calling for that development in a World View article in this week's Nature. Zia says that currently,if there's a global crisis and NGOs, think tanks, and so on, want to know how it might affect food security, they have to phone up experts like him. I called him up to find out more, and he laid out the sorts of events they've asked about.
Interviewee: Zia Mehrabi
The most recent events are really where I've got the calls, and so that's been with COVID, and the main questions there are with mobility restrictions. So, are these mobility restrictions going to lead to restrictions on supply? And so, what's going to happen in terms of harvests in sub-Saharan Africa? What's going to happen in food security in South Africa and southern Africa? Are the agricultural workforce going to be able to get into the field to harvest? Fast forward to Russia – Ukraine war and the kinds of questions that people are asking were, what happens if countries like Germany pull out of using Russian gas? And so, Germany is a big player in terms of fertilizer production, and the real question there was, well, if they pull out, is there enough energy security to produce fertilizers and to maintain it at a low enough price that enables farmers across the world to maintain productivity, and then what will the impact be later on down the line on food access? They're really hard questions to answer, and the main thing that I got from it was that they were all very rushed, and they're all very reactive.
Host: Benjamin Thompson
I mean, that suggests that ways to model things like this weren't in place to quickly answer these questions, despite there being, I'm imagining, a huge amount of data collected about food systems.
Interviewee: Zia Mehrabi
What these two events in particular have really highlighted are gaps in the models that do exist. We have disciplinary divides, so, economists typically work on models of trade, they're working on a much lower resolution, they can't really resolve the dynamics or food transport and things like that, and then you have these massive development of agronomic models, including using satellite remote sensing, look at how green, you know, the land is things like that, but they don't go much beyond the farm gate, and so you have this massive gap, because the models that we do have are so fragmented in terms of their scale, and in terms of what they can actually tell us about how food systems are responding in real time.
Host: Benjamin Thompson
And in your World View, you're saying that these data silos need to be brought together to allow for the modeling of how food flows through the different systems, and specifically using digital twins. Now, for someone who's not familiar with that phrase, what is a digital twin?
Interviewee: Zia Mehrabi
The idea of a digital twin is a digital representation of reality that can be used for stress testing critical failures of a system. The concept really came from aerospace engineering, and when it comes to food systems, the idea is basically you hook up as they do in aerospace engineering, the machines, the environment with sensors to tell you the state of the system, and then you model the system in real time. People have been looking to develop, and have been developing, digital twins of farming systems, but when it comes to food systems, this is something that just hasn't been tackled.
Host: Benjamin Thompson
And what does a fully realized system like this look like?
Interviewee: Zia Mehrabi
It looks like a model that can represent food flows from production, through processing, through to consumption. That's the basic model of what a digital twin of a food system would look like. Now to make it a digital twin, of course, we need sensing, so we need sensing to give us an idea about how food flows operating in real time.
Host: Benjamin Thompson
And how does that differ then from existing modeling exercises say?
Interviewee: Zia Mehrabi
The fundamental difference is the physical realism. To bring these things together rather than try and solve part of this problem in different places. So, for example, scientists have worked to build abstract network models of how food flows, but what we haven't seen is a representation of how food flows over physical infrastructure. We need physical representations to really have an idea about okay, well, what happens if you shut off this port? What happened if you had an extreme event, such as a heatwave in one particular location? If you had a labor force strike? What would happen if all of those things happened, maybe not in the same year in a concurrent set of years? How would that stress the food system? What kinds of responses would we need to put in place to ensure that the most vulnerable are still able to eat and not go to bed hungry at night? That's the kind of question that you can answer, but we can also use them to respond in a much faster way than simply calling up experts to ask them, ‘What should we do?’, ‘What's happening right now?’ and so forth.
Host: Benjamin Thompson
And in your World View, you've summarized some of the hurdles to making this happen, and ways to make sure that access to these digital twin systems is equitable, and one of the things you highlight is the issues that could come to pass, if digital twins are developed by private companies, say, who maybe have the infrastructure and the setup to be able to do this quicker than anybody else.
Interviewee: Zia Mehrabi
Exactly, so, you know, that is definitely a risk, and if they're developed behind closed doors, then the public won't benefit as much as they could. The other component there is that there's a strong financial advantage to having information on how food systems operate, so there's an incentive for keeping these things behind closed doors, but there's also an incentive for creating a data sharing environment, so that not only can the public benefit, and food security be maintained and improved, but also that businesses can maintain the resilience in face of shocks, because the stability, and the predictability of their revenues is being brought into question by these major shocks, not the least, climate change and extreme weather events are associated with it. Again, this isn't something that will come overnight. This is something that needs to be ushered in by an independent body, such as the UN, and governments needs to be there for this to happen.
Host: Benjamin Thompson
And of course, you're calling for this to happen. What do you think happens if digital twins aren't developed, you know, if business as usual carries on.
Interviewee: Zia Mehrabi
I mean, if business as usual carries on, it doesn't look rosy at all. There are a number of factors which lead me to say this, the population is increasing, there's higher corporate powering food systems, there is climate change, we see other instabilities, political instabilities, this gives you just some ideas about the fragilities that we're currently in, and that will come into the future. And so, without foresight, what will happen is we'll continue to have a reactive approach. I see it as a massive missed opportunity that eventually can lead to many more lives being affected by things like famine. If we don't step up and build better food systems models, then we're jeopardizing the resilience of our food supply.
Host: Benjamin Thompson
That was Zia Mehrabi from the University of Colorado Boulder in the US. To read Zia’s World View, look out for a link in the show notes.
Host: Nick Petrić Howe
Finally, on the show, it's time for the Briefing Chat, where we discuss a couple of articles that have been highlighted in the Nature Briefing. Ben, what have you been reading this week?
Host: Benjamin Thompson
Well, this is a story that I read about in Nature, and it's based on a Science Advances paper, and it focuses on a genetic study of the stray dogs living in Chernobyl, and what they could maybe teach researchers in the future about the effects of long-term radiation exposure.
Host: Nick Petrić Howe
Yeah, well, I mean, obviously, when I think of Chernobyl, I think of the big nuclear accident that occurred there many years ago now, and so I guess that had quite a big impact on the surrounding area and the wildlife around there.
Host: Benjamin Thompson
Oh, 100%, and it was 1986 that the disaster happened at the Nuclear Plant near the city of Chernobyl, which is in Ukraine, but at the time was part of the Soviet Union. And of course, a huge amount of radioactive material was spewed up into the air and spread very wide, and the immediate impacts of the accident at Chernobyl, were obvious, a number of firefighters and workers of the plant died of radiation poisoning, and in the surrounding area, pine trees withered and lots of insects were eradicated, but what's less clear, is the effects of long-term lingering radiation in the area, and what effect that has on the animals and plants living near Chernobyl, and this is where the dogs come in.
Host: Nick Petrić Howe
Right, so, are the dogs like a marker for how things are impacted by radiation over the long term?
Host: Benjamin Thompson
Yeah, I mean, it seems like they might well be. After the disaster, teams were sent in to try and euthanize any stray dogs that were left when the city was evacuated, because there were fears that these dogs would spread radiation to further afield areas, but it seems like some of them were missed, right, and they have been breeding since and estimates suggest that maybe there's 800 living in or around the nuclear plant. And to find out a bit more about them, a team of researchers went and collected some blood from a few 100 of these dogs, and this was part of a volunteer mission to provide veterinary care to these stray dogs, right, and it's led to some rather interesting findings, and the main one is that the DNA analysis from these blood samples reveals that these dogs aren't newcomers to this area. If you compare this to the DNA of free roaming dogs in Eastern Europe, the dogs in Chernobyl haven't gone very far, and they’ve kind of stay put, so the fear that they would track radiation around isn't the case, and those living closest to the plant are genetically distinct from those living just a few kilometers away.
Host: Nick Petrić Howe
Well, when I think of radiation, I tend to think of radiation causing genetic mutations, has there been some sort of effect of the radiation on them?
Host: Benjamin Thompson
Well, this is a good question, and I think that's what researchers ultimately want to know the answer to, right. So, this is kind of step one is to just find out a little bit about their sort of genetic makeup. And I think, what researchers can do now is look for any potential genetic changes, which might explain how the dogs have adapted to survive in this area, which was kind of unexpected, right, because the levels of radiation immediately after the disaster were huge, certainly in the area surrounding the plant, but actually unpicking exactly what's going on, apparently gonna be really, really tough because there are other factors at play here too, like any genetic changes might be due to inbreeding, for example, or, you know, other pollutants that aren't radiation based, but the researchers say that this represents kind of a unique opportunity to study the effects of long-term, low-levels of radiation on a large mammal, say, and certainly one that lives in places like people and, and kind of has a similar diet to an extent, because there's been quite a debate about what the effects on humans might actually be.
Host: Nick Petrić Howe
And so, what does this mean for researchers? Like, what could be the uses of this?
Host: Benjamin Thompson
Well, yeah, that's a good question. It seems like there are a bunch of places where this would be useful to know, like, people working in other nuclear plants, for example, folk who have to undergo repeated medical procedures, perhaps as well. And of course, when we think far into the future, of course, space exploration, you know, we've talked on the show before about how radiation levels are a lot higher out in space, and exposure times can be much longer, so, what sort of effects could that have? But of course, these are all fairly far into the future, Nick, I think what's interesting here is this is step one, and those questions can perhaps be answered as we move further down the line.
Host: Nick Petrić Howe
Well, interesting stuff, and I want to take us from Chernobyl dogs to cocaine hippos, because that's the story I've been reading about in this week's Nature. So, there's a news article about some hippos that used to be, well, kind of the property of drug lord Pablo Escobar, which later escaped in Colombia.
Host: Benjamin Thompson
Yeah, this is a story that I'm kind of vaguely familiar with, I guess, because I've seen the Netflix show, for example, and it seems like Pablo Escobar collected a whole menagerie of animals. And now of course, he is past tense, he died quite a long time ago, but the hippos have remained.
Host: Nick Petrić Howe
That's right. So, the hippos escaped from his compound and went into the area surrounding it, and since then, they've kind of been doing what animals do in a new environment, they've been breeding, and they've been multiplying. So, there were originally four hippos, one male and three females, and now estimates are there around 150, so they've certainly been multiplying, and as often with this sort of thing, when there are invasive species in a novel habitat, researchers are concerned about the impacts it might have on the environment.
Host: Benjamin Thompson
Yeah well of course, hippos don't traditionally live in Colombia, and what effects could their introduction maybe have in the area of which they're now living?
Host: Nick Petrić Howe
So, this is all happening around the Magdalena River, and one of the key things is they may displace native species, like there are endangered species, like the Antillean manatee that have a similar sort of ecological niche as the hippos, but the hippos may well be able to out compete them because the very large animals, they have no natural predators in Colombia, and as I say, they've been breeding so they seem to have been doing quite well. They could also potentially cause toxic algal blooms. So, where the hippos are present, there's a lot of basically nitrogen fertilizer from the hippos doing their business, and that could cause sort of these algal blooms, which can then have knock on effects for the aquatic life in the region, and there's also the concern that they could attack people, hippos can be quite vicious, and they're pretty deadly animals.
Host: Benjamin Thompson
So, a bunch of things on the list there. Nick, what's being done to do something about?
Host: Nick Petrić Howe
Well, that's sort of the crux of this news article, so there's been a bit of an ongoing row for many years about what exactly to do about them, because whilst there are these risks, they have been quite popular amongst some people in Colombia, and in 2009, for instance, there were pictures that was sent round that showed the military shooting one of the hippos, Pablo Escobar’s male hippo named Pepe, and this sparked a lot of outrage, there was a bit of an outcry about this, and that sort of ended in a kind of stalemate with the government not really wanting to anger people, but also wanting to try and do things to prevent this sort of damaging effects that the hippos could have, and then there are also the animal rights activist who want to try and protect the hippos lives, they don't want the hippos to be killed, even though researchers say that in order to protect as many hippos as possible, you may need to cull some to prevent the numbers escalating.
Host: Benjamin Thompson
So, a tricky needle to thread, and you say something that's been discussed at length for quite a while it seems, like where do things go now, do we think?
Host: Nick Petrić Howe
Well, recently, the Colombian environmental minister didn't say directly, but sort of alluded to the fact that they may protect the hippos, and since this news article was published in Nature, there have been other articles published in a variety of publications, including the Washington Post that said that maybe a plan to send these hippos to sanctuaries in India and Mexico. So, there could be a way to not have to cull the hippos, but also remove them from this environment where they shouldn't really be.
Host: Nick Petrić Howe
Well, that is quite the story, Nick, and my goodness, we've covered some ground on the Briefing Chat today, but let's leave it there for this edition, and listeners, for more on these stories, and where you can sign up for the Nature Briefing to get more like them delivered directly to your inbox, check out the show notes for some links.
Host: Nick Petrić Howe
That's all for this week. As always, you can keep in touch with us on Twitter, we’re @naturepodcast, or you can send an email to podcast@nature.com. I'm Nick Petrić Howe.
Host: Benjamin Thompson
And I'm Benjamin Thompson. Thanks for listening.