‘Tree islands’ give oil-palm plantation a biodiversity boost

Benjamin Thompson

Welcome back to the Nature Podcast. This week, how tree islands could increase biodiversity in oil-palm plantations...

Shamini Bundell

...and the latest from the Nature Briefing. I'm Shamini Bundell...

Benjamin Thompson

...and I'm Benjamin Thompson.

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Benjamin Thompson

Palm oil is a product that's found everywhere. From cosmetics to foods to fuels, it's an incredibly versatile ingredient. Palm oil is made from the small, reddish fruits of oil-palm trees, which are grown in monoculture plantations across vast areas in tropical regions around the world, mostly in southeast Asia. However, the expansion of these plantations to meet the global demand for palm oil has led to widespread deforestation, environmental damage, and biodiversity loss — problems that need to be addressed and reversed. And there's a balance that needs to be struck as well, between restoring the environment and maintaining agricultural productivity to protect economies and the livelihoods of the local people who work in the industry, many of whom are smallholder farmers. This week in Nature, there's a paper from a group of researchers working in Europe and Indonesia, who have attempted to find that balance in oil-palm farming. They've spent five years looking to see whether planting islands of native trees among the palms in a large plantation could improve things like biodiversity without affecting yields. To see what they found I spoke with lead author Clara Zemp from the University of Neuchâtel in Switzerland, who told me about the origins of the tree Island idea.

Clara Zemp

So the tree island concept was actually developed in let's say, early 21st Century, the initial idea was to use this approach to restore degraded lands that was unproductive, so abandoned lands, and to reforest it on the long term. It was supposed to be more economical, because you don't need to plant as much trees as if you would plan the entire area. It is also supposed to provide ecological benefits for biodiversity. And for restoration of the landscape. It was also suggested as a way to mitigate biodiversity-loss in productive landscapes. So not only abandoned lands, but also in lands that are agricultural. And the idea is that by having these trees in the landscape, they provide stepping stones for biodiversity. So they allow species movements, and they can host certain communities of species, which are otherwise not possible to thrive in the landscape.

Benjamin Thompson

I mean, let's talk about your three islands then. So you planted 52 of these in quite a large industrial oil-palm plantation in Indonesia. What do they look like? Because they're all different sorts. Right?

Clara Zemp

Exactly. So the 52 Islands differ in the area, the smallest one were 35 square metres, the largest one were 1,600 square metres, and they also vary from zero trees planted, that means it was only natural regeneration, up to six different tree species planted together. And all the trees species that were planted are native to the region, and they were planted between standing oil palms. We also had to remove some of the palms prior to planting in order to provide light and resources for the trees to establish and to grow. But basically, in these tree islands there is a mixture of trees, oil-palms and other plants resulting from natural regeneration.

Benjamin Thompson

And so over a course of five years, then you looked at what happened to the environment, the biodiversity and the ecosystems in these different islands. What did you see?

Clara Zemp

So we found that the tree islands had an increase of, by a factor of 1.5, what we call multi-diversity, which is an indicator of biodiversity that includes all the different components from soil bacteria up to birds and bats. In terms of ecosystem functioning like carbon- and nutrient-cycling, quality of the soil. biotic interactions like prediction-herbivory, we found an increase by a factor of 2 in our tree islands compared to conventional oil-palm monocultures.

Benjamin Thompson

And was there a sweet spot in terms of the size of these islands? Was there one that performs the best overall, I suppose?

Clara Zemp

Well, actually, that's the surprises of our results is that the larger the better in somehow all aspects. For biodiversity we have more species in larger islands for all the different facets of ecosystem functioning was also enhanced in larger islands. So regarding our results, so far, we would say larger islands the better.

Benjamin Thompson

And what else did you see? Were there any islands that didn't quite do as well, for example?

Clara Zemp

Actually, we find some trade-offs between different aspects of biodiversity. For example, islands with larger number of tree species posted high diversity for some groups, for example, for bats, and for herbaceous plants, that but for other groups, like for example, arthropods, this was rather than negatively impacted. So this is somehow showing that there is different responses of biodiversity depending on the type of habitats that we reconstruct with this tree islands.

Benjamin Thompson

Well, let's talk about yield, then, the effect that this had on the output of the oil-palm trees, I mean, you said you had to cut down some of the palms to make space for these tree islands, which I imagined would affect the yield, what did you see in that aspect?

Clara Zemp

We found, as expected, a decrease in the yield-per-area, because of what you mentioned. And also because of the competition between the trees and the oil palms. However, this loss was compensated by a gain in yields of the oil palms that were directly adjacent to the islands. And this increase compensated for the loss-per-area that we found inside the tree islands. So in the end, the entire plantation, or the entire landscape scale, there was no loss of oil-palm yields.

Benjamin Thompson

I mean that to me is quite surprising that these oil-palm trees were more productive when they were next to a more diverse group of trees.

Clara Zemp

Yes, actually we looked a bit more into this effect. And we found that this gain in yields is attributed to a thinning of the oil palm that increased light, that increased resources, which benefitted the first row of the plants adjacent to the island. And this was strong enough to compensate for the loss.

Benjamin Thompson

I mean, one thing that really struck me is that, of course, you've done this trial in a huge oil-palm plantation. And you've shown the effects that you've shown, do you think that this approach would work everywhere, because of course, in maybe a smallholding plantation with much fewer trees, if you're having to cut some down, that might affect the economic yield for the smallholding farmers, for example.

Clara Zemp

So indeed, because we worked in this large plantation of 140 hectares, the percentage of the land that was occupied by the islands was actually less than 5% of the total productive area. Now, if we would have done this experiment in smallholder plantation of a few hectares, of course, these islands would cover a substantial share of the total productive area. But even if the oil-palm yield declines for the smaller farmers, they could have additional incomes from the planted trees that produce fruits that produce wood or that produce latex. So they could potentially diversify the revenue instead of relying entirely on the oil-palm yields.

Benjamin Thompson

And so your paper is out now. I mean, what questions are left to answer do you think about this work?

Clara Zemp

So we have data for five years, but still, oil-palm plantations usually are standing for 20, 30 years. So whether the oil-palm yield will continue to be maintained, this is something very important to monitor on the long term. I think also, from an ecological perspective, I would find it interesting to see the connectivity between these islands. Because so far, we looked at biodiversity within islands, and then the landscape scale. But we do not really understand whether organisms are able to move between these different islands, or whether we have very fragmented habitats.

Benjamin Thompson

And if we look to the future, I mean, I think it's fair to say that palm oil is unlikely to be going anywhere anytime soon. Given that how are you hoping that your research is picked up and used?

Clara Zemp

Yes, I think we have to try to improve the situation in existing plantations. So what we suggest with these tree islands is a way to mitigate this negative ecological impacts in the plantations that are already in place. Of course, the priority for maintaining biodiversity for reducing the loss will be to stop deforestation and to prevent further expansion of oil palm at the expense of forests. However, oil-palm plantations will continue and I think there is potential to expand in degraded lands. So in areas that have been deforested for long-term and that are basically degraded, so there is possibility to mitigate the biodiversity loss in existing plantations without having to deforest further.

Benjamin Thompson

Clara Zemp from the University of Neuchâtel there. For more on the work, look out for a link to the paper in the show notes.

Shamini Bundell

Coming up how CRISPR helped researchers crack the mystery of a deadly mushroom's toxin. But right now it's time for the Research Highlights with Dan Fox.

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Dan Fox

The oldest 'blueprints' ever found might have been used to to prepare for large-scale hunts. Around eight years ago, archaeologists discovered two stone slabs, one in modern Jordan and the other in Saudi Arabia, engraved with what looked like depictions of desert kites, prehistoric human-made structures used as mega-sized traps to capture wild animals. The researchers mapped these engravings and found that the shapes were to-scale copies of the desert kites found in the area. Dating suggests that the oldest of the diagrams could have been made as long as 9,000 years ago, making the engravings the oldest plans for large-scale structures known to date. The authors say these representations could shed new light on the evolution of humans' understanding of space and their ability to communicate this with one another. You can find that research in PLOS ONE.

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Dan Fox

Fossils show that extinct marine beasts called pliosaurs might have grown to be nearly as large as a sperm whale. In 1979, workers digging on a farm near Abingdon in the UK found four fossil vertebrae the size of dinner plates, with the largest almost 27 centimeters across. Researchers examining these fossils along with a fifth vertebrae from another site have concluded they belonged to pliosaurs, the enormous marine carnivores that were abundant during the Jurassic period, around 200 million years ago. pliosaurs had heavy tooth-filled heads like a crocodile's, barrel-like bodies and four flippers. Extrapolating from the vertebrae, the team estimated that the Abingdon specimen would have been between 9.8 and 14.4 meters long, nearly the size of a sperm whale. The authors say that this is clear evidence for a truly gigantic pliosaur species in the late Jurassic, something there has been much debate among experts. You can unearth that paper in Proceedings of the Geologists' Association.

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Benjamin Thompson

Finally, on the show, it's time for the Briefing Chat, where we discuss a few articles that have been highlighted in the Nature Briefing and Shamini what have you got to chat about this week.

Shamini Bundell

So I saw this Nature News article, which is based on a paper from Scientific Reports. And it's basically about a house made of nappies, roughly speaking and I was like, 'yeah, I want to talk about that in the Briefing Chat'. And it is kind of about how to try and make more sustainable building practices. Can we reuse waste nappies, basically as a building material?

Benjamin Thompson

Goodness, okay. Well, I have a lot of questions to ask about this. And just for clarity, when we say nappies, we mean diapers, right, and used ones as well. I mean, where do we start? How do you build a house out of used nappies?

Shamini Bundell

Okay, so the background to this is some of the problems that they're trying to solve here, or the kind of problems that exist in the building sector of which there are many. So you've got the fact that a lot of construction uses concrete, and cement, and concrete and cement have a huge greenhouse gas emission footprint. So potentially 7% of global greenhouse-gas emissions, and uses a lot of sand. I made a film about this recently, actually, which you should check out on our YouTube channel. But sand is a limited resource sand's going into concrete, concrete, making lots of carbon dioxide. So that's kind of a problem. Then you've got the problem of affordable housing. So this project is based mostly in Indonesia, and in Indonesia, and other low- and middle-income countries, you've got growing populations, and increasing demand for low-cost housing, of which building materials is a huge proportion of the cost of a house. But when you've got a growing population, you've also got more babies, more nappies, diapers. So these researchers were basically trying to figure out whether one problem could be used to sort of help solve another.

Benjamin Thompson

It does seem like a bit of a leap to go 'what should we use instead of stand? I know soiled nappies. I mean, let's unpack that a bit, I guess, maybe that's an unfortunate choice of words. But what do they do then to try and use these in the construction industry?

Shamini Bundell

So apparently started off quite small-scale. One of the researchers had a toddler, got some nappies, washed them, luckily, dry them, shred them, and then basically testing that material to see whether it is strong enough to replace different proportions of the sand in concrete. So they sort of basically made different mixes up with different proportions and pressure tested them. I think it was mostly the compressive strength that they were interested in. And it also had to obviously, like meet the particular building-codes, and they found that depending on the use of the concrete, for some of the material, they could replace up to 40% of the sand that would have gone in with this shredded-nappy mix. So 40% is sort of the top end, at the bottom end, if you've got a sort of weight-bearing structural component like the columns and beams, those would need a much lower proportion like 9 or 10% of the sand that you can replace.

Benjamin Thompson

I mean, I guess we've kind of been making light of this a bit, but that actually is quite a substitution, right, that can be useful in terms of emissions.

Shamini Bundell

Yeah, so they did a sort of demo of this, they built a small single-storey house, it didn't fully use cement for sort of ease, some of the beams were metal instead, but in their sort of small single-storey house, calculated that 27% of the sand that would have gone into it can be replaced by this nappy waste, that decreases the taller your house goes, because then you need more of these sort of structural components. But yeah, they built a little nappy house, basically.

Benjamin Thompson

Amazing. And I guess this is a proof of concept, I'm sure. And I imagine there are a multitude of other problems that need to be overcome before we can expect to see this being used.

Shamini Bundell

Absolutely. Yeah, very much a sort of demonstration of what's possible. A huge problem with it, actually, is the fact that at the moment, there's very little recycling of disposable nappies. And you know, in most places, they're not separated out, you know, it's not like we have our plastic-bottle recycling, where you put it all into different bins, it would need a whole system in order to get this waste, and then obviously, transport it and you know, the whole setup. So the practicalities of it aren't there yet, and people would maybe have to look at whether once you sort of factor all that in, it's worth it or not, is it better than other options? So a chemist who has commented on this paper for the news article sort of said, well, it might be more environmentally friendly, if the walls were actually made of wood-based composite materials instead of concrete. So there's a lot more to be done to look at what's best here.

Benjamin Thompson

Well, I will say having changed an infant's nappies, many times, you brought back a lot of memories of emptying the nappy bin, which I didn't necessarily want today.

Shamini Bundell

Sorry, Ben.

Benjamin Thompson

But let's move on quickly, hastily, to our next story. And it's one that I read about in Nature. And it's all about some research that's been looking to find an antidote to a very, very poisonous mushroom. And it's called the death cap mushroom.

Shamini Bundell

I love mushrooms. I love going on walks and spotting the different mushrooms. But I've definitely heard that if you're not a super expert in knowing exactly which species are safe to eat, you could easily kill yourself. And I guess the death cap mushroom is one of those lethal ones.

Benjamin Thompson

Yeah, I mean the name kind of gives it away. Right? But you're absolutely correct, like it is a potentially lethal mushroom. And a death cap mushroom is about 15 centimetres tall, it can have a tan or yellow, green cap. And it does look like a lot of edible fungi. So a lot of people do accidentally eat them.

Shamini Bundell

Where does it grow?

Benjamin Thompson

Well, it grows all over the place, actually, across the world. And it can be really, really detrimental to someone's health if they do eat it. Vomiting, seizures, severe liver damage as well. And of course, death. And hundreds of people a year die from eating poisonous mushrooms as I understand. And the death cap is responsible for 90% of these and 1,000s of hospitalizations, as well. But this isn't a new problem, like, death cap poisoning has been written about through the ages, right? Like it was implicated in the death of the Roman Emperor Claudius, whose though to have died from consuming mushrooms in AD 54. And there are other stories there. But fast forward to today, and there are very limited treatments. But despite all that's known about these mushrooms, you know, it's been a bit of a puzzle as to what their actual toxin is doing inside the body.

Shamini Bundell

Oh, right. So we don't know much about the biochemistry of how it actually kills someone.

Benjamin Thompson

Yeah, that's right. And that's what the researchers have been working on here. So it was known that these mushrooms contain a toxin called α-amanitin. And what the researchers have done in this new work is they've used CRISPR to figure out what's going on, okay. So they use the CRISPR-Cas9 gene editing to make a pool of human cells. And in each of these different ones, a gene was mutated so that it didn't work, okay, and then exposed the cells to the death cap toxin, to see if any of these mutations helped the cells to survive, okay, and they found that cells lacking a functional version of a gene called STT3B, were able to survive the death cap toxin.

Shamini Bundell

Wow, that's quite a sort of scattergun approach, isn't it? Rather than sort of trying to look and see what protein this toxin is interacting with. It's let's do some gene editing and see which cells cope better. So they've identified this particular gene. So what does this gene do?

Benjamin Thompson

Yeah, well, this gene encodes an enzyme involved in a biochemical pathway that adds sugar molecules to proteins. Okay, and so breaking this gene and then breaking this pathway meant that the toxin couldn't get inside the cells. And the researchers behind this work say this was a total surprise, right? They had no idea that this was going to be the case, and nobody knew this before.

Shamini Bundell

Is this the kind of thing where what they really want to know here is the mechanism, it's not like we're all going to get gene edited to give us immunity to death cap mushrooms, we can go around eating them it's that they wanted to know See how it worked and this was the method.

Benjamin Thompson

Yeah, that's right. And there's still a lot of questions about exactly how this works. But they identified this pathway. And then in the next step, they've used this knowledge to screen some chemicals to look for ones that could work as antidotes.

Shamini Bundell

Oh, so how do you go from knowing this sort of pathway and the genes involved to finding a substance that might help?

Benjamin Thompson

Well so they looked over 3,000 chemicals for ones that blocks the action of STT3B, okay. And they found one, and it's called indocyanine green. And this is a dye that was developed by the photography company Kodak in the 1950s.

Shamini Bundell

Oh! What?

Benjamin Thompson

Right. And it's currently used in medical imaging to visualize blood vessels in the eye and blood flow in the liver, for example. And they tested it to see what effects it had. And in mice about 50% of mice treated with indocyanine green died from poisoning compared to 90% of those who weren't treated. So it's got some potential.

Shamini Bundell

Yeah. And is this, you know, anywhere near being a sort of viable treatment? Like if someone you know, knew that they'd eaten this mushroom, could they quickly take this substance and potentially save themselves?

Benjamin Thompson

Well, I'm gonna say there is a lot researchers don't understand about this, that isn't a viable option, just yet. But indocyanine green is approved by the US Food and Drug Administration and the European Medicines Agency for its current use in imaging. And it's known to be safe at certain doses. So that's a plus. Right? But it really needs to be tested in this situation in humans. And that is a challenge because finding funding is challenging, but also the need to find people who've accidentally eaten death cap mushrooms.

Shamini Bundell

Quite quickly as well, I'd imagine.

Benjamin Thompson

Absolutely right. Timing is super important, because these mice were treated four hours after the toxin exposure. And humans often turn up to hospital, apparently 24 to 48 hours after exposure, so much later. And obviously, they're much sicker at this point. And it might be too late. So there's a lot to learn there. But I think the method that the researchers have used to find this has got some promise. So they've used it previously, to develop a method for finding an antidote to jellyfish venom. And there's some hope that it could be used to find antidotes that can be applied to other toxins and other situations.

Shamini Bundell

Yeah. And I definitely, you know, wouldn't have thought back when we were sort of learning about oh CRISPR-Cas9, this new kind of gene editing, so many potential applications, so many different ways of using it. So that's fascinating. Well, thank you for that, Ben, and listeners. If you want to find out more about these stories, and where you can go ahead and sign up for the Nature Briefing, so you can get stories like this yourself, check out the show notes, where we'll put some links.

Benjamin Thompson

And that's all we've got time for this week. But before we go, just time to remind you as ever, you can keep in touch with us on Twitter, we're @naturepodcast, or send an email to podcast@nature.com. I'm Benjamin Thompson.

Shamini Bundell

And I'm Shamini Bundell. Thanks for listening.