Instant Genius - Are we facing an insect apocalypse? - Brad Lister

Episode Date: February 27, 2019

When Professor Brad Lister returned to Puerto Rico to track insect populations, he found he was only catching a fraction of the amount he’d seen 40 years ago. When he analysed what he’d caught, he saw a 98 per cent decline in insects on the ground. What’s causing this huge loss, and what does it mean for the future of our planet? Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Music just as the artist intended. Visit name audio.com to learn more. I'll see how you can protect, conserve the upper levels of the food web, the insectivores, the birds, the reptiles and amphibians without protecting the insects. and that's a very difficult task. You're listening to the Science Focus podcast from the BBC Focus magazine team with the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world.

Find out more at sciencefocus.com or look out for us in your app store. Hello and welcome to the Science Focus podcast. I'm Sarah Rigby, online assistant at BBC Focus magazine. When Brad Lister first studied lizards in the Lucchio Forest, in Puerto Rico in the 1970s, the sticky plates he put out each day came back black with insects. When he returned in the early 2010s, the same traps would catch only one or two struggling bugs. When he analysed his results, he found that on the ground, 98% of the insects had vanished. In the canopy, 80% were gone.

His study was published late last year, and shortly after, reports from other scientists and concerned citizens came flooding in. Studies showed the insect population in Germany, had been similarly devastated. A pilot, who, decades ago, had to wipe his windscreen clear of bugs after flying in the Arctic Circle, now had a clean screen after every trip. We ask Brad how alarmed we should be about this decline in insect numbers. What would a world without insects look like? What implications does this have for the human population?

And is there anything we can do ourselves to ensure the insects around us thrive? Here's BBC Focus editorial assistant Helen Glennie talking to Professor Brad Lister. You recently published a study about the declining insect population in a forest in Puerto Rico, and it caused a bit of a stir. Can you give me an overview of that study? Sure. That study originated back in the 1970s when I went down to Puerto Rico for the first time to really investigate the ecology and evolution of these Anolis lizards,

which have become sort of a paradigm for ecological and evolutionary studies. I was interested in competition between the species and the forest, decided that really couldn't say much about competition unless we measured their food supply. So we did that. We developed this sticky trap method, and we did sweet nets through the forest. So that formed the baseline for the more recent analysis where I went back to the same study area, used the same techniques, and replicated the results for the more recent analysis. where I went back to the same study area, used the same techniques, and replicated the results for the insects. And we also censored some of the annoles in the forest that had been there back in the 70s. And what we found was astonishing.

I mean, within a couple of days, we knew something was terribly amiss in that forest, where plates, we had these sticky plates, we raised into the canopy and then also put out on the forest floor to capture the insects. In the 70s, after 12 hours in a tropical forest, we'd uncover the plates early in the morning and then cover them back up late at night. The plates would be just black with insects. But the first couple of days, Andreas Garcia and I were redoing the study. We would get either no insects at all on a plate or maybe a few lonely insects captured in the canopy and the ground traps. And it was just amazing.

I mean, we just, we're totally unexpected. We actually knew, well, we're going down there to test in the field and hypothesis by Curtis Deutsch and Ray Huey and others that tropical insects would be very sensitive, extremely sensitive to small changes, increases in temperature, because they had evolved in such a stable environment and they really didn't have the capacity to respond to much higher. temperatures than their optimum. And that this being the first field investigation of that hypothesis. I mean, people had done experiments in the lab with insects, tropical and tropical, and that seemed to be the case that tropical instances are much more sensitive to climate warming,

but to temperature warming. And we seem to certainly support the Deutsch-Huie-at-all hypothesis. And so did you understand the implications of what you're was seeing straight away? We immediately knew that the forest was in big trouble. We immediately wanted to try and take a look at, a closer look at the insectivores, because if the food is just imploding, you would expect the species that eat the insects higher up on the food chain would also be declining. So we were very fortunate to have not only our data on the annullous lizards, but also data taken at the long-term ecological research study at Alt Verde, which is about five miles from our study area, and the scientists there had gathered long-term data on birds, on walking stick insects,

on canopy insects, and on frogs. So we had that data and analyzed it. It was freely available on their website. And what we expected actually was occurring that in parallel to the decline in insects, birds were declining, insectivorous birds in particular, the frogs were declining, and canopy insects from other studies by Leo Showalter over 20 years. They were also declining. And the declines weren't small either. We had a 98% decline in the ground samples between the 1970s and 2011-2012. these studies from El Verde were indicating about a 70% decline in insects over a 20 to 30 year period, and about a 70% decline in birds as well. Wow, 98% decline in ground insects is just staggering.

Do you think you can describe why the insect population is so important? What would a world without insects look like for us? Unimaginably degraded. They are the food base for so many species higher up in the food chain. And the insectivores are, of course, eaten by other predators. So it's a cascade close to the bottom of the food web all the way up. So you'll see what we saw in Puerto Rico happening most likely throughout the world. The recent biological conservation article where they looked at many, many different studies.

of insects declines all over the planet. It's clearly a global phenomenon, which many of us thought, but we hadn't looked at a synthesized data set that these people did. So it's happening all over, except for the tropics. And they only had three data points for the tropics in that study, ours being one of them. So there's a posity of knowledge about how tropical insects are doing. we really need to get replications of our study throughout the tropics so we understand how widespread this phenomenon is. If it's happening in, say, you know, the Amazon, that the

insects are imploding, then the implications are very disturbing because you can't, I don't see how you can protect, conserve the upper levels of the food web, the insectivores, the birds, the birds, the reptiles and amphibians, without protecting the insects. And that's a very difficult task. Yeah, so then what about the effect as well on things like decomposing food waste and soil quality and, you know, pollination of crops and that sort of thing? Was there an effect there? Yeah, I was absolutely, you're absolutely right.

Those are key ecosystem services of insects. In particular, well, they're all important, but pollination is a major concern. The insects are responsible for about 80% of all the pollination of natural plants and ecosystems around the world, and also for food crops. So if this crash of insects continues and looks like we're going to get warmer and warmer, and we pointed the finger, all of our data pointed the finger right at climate warming, at least for the lukea or rainforest, then we're going to see a collapse of our food crops. They're going to see a total change in ecosystems around the planet with perhaps wind-pollinated species becoming much more abundant.

A lot of the insect pollinated species declining in abundance, perhaps going extinct. So the consequences are dire for ecosystem services. that we depend on for our very existence and for the quality of life that we now have. Yeah. So do you know off the top of your heads what crops are insect pollinated rather than wind pollinated? What are the things that we're going to lose out on? Well, I have one example I actually give.

I'm not an expert in the agricultural component of all these changes. But the almond crop in California, they're not enough bees anymore to pollinate the almond flowers. And so they, every year, 50% of all the beekeepers in the United States trucked their hives to California, to these, I think it's a million acres or so. And they stay there for a while letting their honeybees pollinate the almond crop. Now, that costs a huge amount of money. And I certainly, and others have concurred with this, can see the day coming fairly quickly when we will lose for whatever agricultural crops or need insect colonized, we're going to start seeing a decline.

Now, and the counter that argument was that in the temperate zone, so we really should distinguish usually between the temperate zone and the tropical insects and what's happening. But there was a paper recently that said, you know, the insect's metabolism is going up in the temperate zone, they're not nearly as sensitive to climate warming as the tropical insects, and they're going to get voraciously hungry. So they may, at first at least, start eating more of the crops than they do now, and it was substantial increase in the insect herbivirion crop plants. But eventually, once the temperatures get up above two, three degrees centigrade in the temperate zone, you're going to see a collapse of insects up here. That's what we're predicting,

we're predicting as well. The declines that we're seeing now, do you think that they are just going to continue? And if we're looking at something like a 98% decline at the moment, are we getting close to extinction of certain species? Yeah, that that's a, that's the core question. And as you probably are aware, biologists are reluctant to, you know, say the extinction, word because first of all, it's so hard to document, you know, any population is really extinct. But I think certainly the biological conservation society paper came right out and said over the next 10 years, they expect 41% extinctions of all insect species that they were able to get data on. So we did go out on that limb because it was so drastic for the tree frogs in Puerto Rico

and predicted that within 20 to 30 years, many of the populations that we looked at would be extinct, probably all of them. If you just follow the regressions down to zero. So, yes, the insects, it certainly, given the biological conservation paper, given other articles that have been coming out and giving our data, the declines are very rapid. and if the temperatures keep rising, in most areas, we expect mass extinctions of insects. So you're sort of pointing the finger at climate change and the warming of temperatures around these areas. Can you tell me how you arrived at that conclusion? What did you measure and what did you see? Yeah, just to qualify that, the caveat is that it's for the lucia rainforest.

There are many, many different causes of insect declines, as far as we can tell. In the temperate zone, it's more habitat disturbance and pesticides. In the Leukea rainforest, that forest has been protected for many hundreds of years, actually, especially the past hundred or so. So that disturbance isn't a factor. Pesticides in Puerto Rico have declined about 82% over the past 30 years or so, because they've transitioned to an industrial economy. The forest around the Lugio Mountains that was clear-cut has now come back, and it's a full forest.

So there weren't many other factors in this rather pristine forest that we could point a finger at. And all of our analyses certainly were indicating very strongly that it was climate warming. We looked at a lot of other variables, and they were. important, but increasing temperatures were consistently the most important. There were several powerful statistical techniques that we use, one being v-no causality. Cosality, you know, statistics is mute on causality. It just doesn't have much to say about it, but new techniques that have been derived over the past 20 or 30 years allow us to assess causality. Does variable X cause changes in variable why. And the evidence that we discovered using veno causality was that the strongest possible

causal connection between the declines of the species in Puerto Rico and the increasing temperatures. Wow. And it's almost, it makes it quite a bit scarier that Lequia forest has been protected for hundreds of years and they're still experiencing these declines. It kind of shows that we can't just like wall off bits of national park and think that everything's going to stay exactly as it was. Yes, that's a central point. It's an insidious effect because we can make the parks as big as and we should. We need more parks, obviously. That's going to help.

But still, it's a threat from within and without, and it's hard to escape. Now, one of the things that we've been talking about is to try and get more parks with greater topographical diversity. because they will have a much greater range of microclimates that conserve as refusia for the insects. And we know that many species in the tropics, when they can, are moving uphill. They're going to cooler temperatures. And that's true in the Luquillo forest as well. And that will by time, that will perhaps allow them to adapt better to the changes and increases in temperature.

but if we keep going, it's difficult to see how even those lifeboats will be available to many tropical species. But we've got to try and we've got to have more reserves, I think, with these range of temperatures that the insects can take advantage of. Yeah, so what is it exactly about the increase in temperature that's so threatening to insects? Yeah, I don't know if you saw this paper that came out. a couple of weeks ago, I think. And it is, it could be, I shouldn't say it is, it could be something of a smoking gun for one of the causal mechanisms behind these declines. What they did was in the lab, they used flower beetles, and they exposed the male flower beetles to pulses of heat beyond, you know, on the range of what they'd experienced during heat wave and natural environments. And after just

two pulses, pretty much 100% of the male flower beetles were sterile. it just shut down sperm production. So if that's, we've got to, you know, look at that in natural habitats, but if that's happening, that is really frightening. And it may be one of the effects. We looked at the effects of El Nino in Puerto Rico. El Nino is the warmer, drier phase of the El Nino southern oscillation. And every four years or so, you get a Lovina, which is cooler and wetter and then an el nino, which is, you know, drier and hotter, we could see the clear fingerprints of those increases in temperature when an el nino arrive on the abundance of insects. It was amazing to see the sensitivity. So then we looked at increases in the heat waves within the Lujillo

forest, and we defined that as temperatures above 29 degrees centigrade. So we started getting back 20 years ago, we couldn't find any days above 29 degrees centigrade, and that went up to 42% by around 2011, 2011, 2012, 42% of the days with very hot temperatures. So we think that's a major factor. We did, you know, stated in the paper, and the reduction or total loss of sperm in male insects might be one of the outcomes of those pulses of hot temperatures. Okay, so more so than temperatures killing off the insects, it's making them infertile and they're not reproducing. Yes, it probably has a, you know, increasing temperatures have a host of effects on

animals, vertebrates and invertebrates. Ectotherms, a cold-blooded species, are particularly sensitive to the increases. But this is certainly one of the major effects. But we have to, again, get more data and replicate that in natural environments. Other possibilities that we mentioned in the paper is that the disconnect between the insect's food and the actual availability of the foods. So plants and insects can get to be in different phenologies. So the insects will starve to death. The increase in temperature might allow diseases to be more virulent for species because, in theory,

weakens their immune system, reduces their ability to respond to predators as well. Scape, flying. There's a whole host of fitness decreasing effects on vertebrates and invertebrates from increasing heat. But we think that this lead that these people have given us on the effects on sperm counts may be one of the most important. You mentioned as well that moving to higher temperatures could be. potentially by time and it might allow these, or some species, a chance to adapt. Do you know how long this kind of adaptation takes for insects?

How much time would we need to buy? That's a great question. I do know that there are increasing numbers of examples for arthropod adaptation to increasing temperatures. I don't know how long that has taken, but certain one would think that most of the increases, say in the world and in the Sluquio forest, we also looked at Mexico insects populations and they were down 86%. That was just a tropical dry forest, but we decided, hey, we did this in the 80s. Why don't we go back and take a look at the Mexican forest?

And we found similar declines. So this is a very, very forceful selective pressure on insects, at least in the tropics right now. And the response, given the many generations that insects have within a much shorter period of time than vertebrates, is one would think is letting a host of insects gradually adapt to the rising temperatures. This is happening so fast that that might be the case with somewhat less fecund insects. but I don't know of any paper that's assessed what percent and how rapidly insects are adapting. What sort of evidence have you seen that contradicts this idea of the fact that there's a decline in insects? Is there anything that's pointing back the other way? Well, I mean, the Crafell study, just for one, for a counter example,

they looked at defects of temperature and they found that there was a somewhat, a, I think significant positive effect of increasing temperatures on all of those insect populations they studied in those reserves. Now, that effect was predicted by Deutsche and Huey at all that in the temperate zone, you would, for a while, start to see an increase in insect populations and an increase in fitness as a temperature warmed. But that would, I'm not sure exactly what the threshold was, but after a certain rise in temperatures in the temperate zone, that would start to disappear and you'd see a decrease.

So, you know, in the temperate zone, maybe, certainly the biological conservation article pointed to similar effects in the temperate zone that weren't quite as devastating as we're seeing in the tropical areas. But, you know, overall, it's temporary, as far as I can tell. So you guys have published this paper, and there seem to have been a raft of other studies that have come out recently. Is this because it's a phenomenon that's only been happening over the past 40 years, or is it because these studies are only starting to get done now? I think it's both that there certainly was recognition, I think, in 1975, and the person who, the scientists who coined the term climate warming, came out with an article in 75 saying, listen, this is happening, you better pay attention.

I think he's very recently deceased. And so that we knew back then, but it took a while for enough data to accumulate that people were willing to go out and sample forests for 20 years. And in that regard, a lot of these studies take a long time to do if you want to have the data, and they need historical data to do that with. in the tropics, not much historical data, unfortunately.

But I've been getting, well, I reviewed a paper from a person, a scientist in Norway, who around the Arctic Circle has been doing the windshield effect, sampling insects by driving his truck back and forth over 20 miles, year after year for 20 years. And in Norway, northern Norway, the insects have also plummeted. And yesterday, I got a email from a bush pilot who regularly flies above the Arctic Circle. He said 20 years ago, when they landed from one of their expeditions, they had to scrape

the insects off their windshields of their plane. So this is an extension of the car windshield effect. And he said in the past few years, they hardly get one insect on the windshield. So it's not scientific, but I think it's a very, very revealing anecdote. And it was frightened me that even from pole to pole, literally, we are seeing these declines. Yeah, so do you know enough about this now? You just mentioned that it frightens you. When you get new information in like that, is it still enough that it causes a bit of an emotional reaction? I think, you know, the past few weeks, a couple of months since our articles published and seeing the other articles come out,

and there was one from Germany you probably familiar with from Kreyfeld, where they looked at, I think, 60-plus biological reserves in Germany, and the flying insects were down 76% in biomass. So that, you know, it is that the accumulation of these examples and the realization that this is a terrible threat to the natural world and to humanity that will only get worse. And if it gets much worse, we just don't see how we're going to avoid the collapse of the natural world and the collapse of human beings. civilization. I really believe that now. I think that's what we're looking at. And hence, it's extremely disturbing, but also extremely pressing that we collectively have a global effort to address these issues. Yeah, so how do we do that? What can be done to stop this collapse? Well, it's going to take, at the base of it, it's going to take a lot more urgency and willpower

than any nation has shown so far. And some are bad and some are good, but we really do need a concerted effort now. And what it's going to take is going to take some money to, first of all, address the two major drivers that lie behind all of our problems. We're 100% over the carrying capacity of the planet. We have, what, seven plus billion people now that's going to go up to nine or ten billion, We are absolutely exceeding the ability of the earth to sustain our population. It's totally unsustainable.

So we have to deal with population increases, and we have to deal with all the outfall of rising population being mechanized agriculture, which is tremendously destructive. And it's not just the pesticides. and the landscape, it's a variety of other outfall from the way we have, you know, started to practice agriculture to feed all those people. So those are two of the major drivers. We absolutely have to stop decimating the world's forests and clear-cutting. That was curtailed for a while in Brazil and the Amazon, but now is heading back up. So there's a host of factors that are on sort of overarching drivers of what's happening. And of course, climate warming, we think being

one of the major ones, and we have to follow the UN recommendations. We have to decrease emissions as soon as possible. And then we can buy some time. I really think we do have time, but the window for action is decreasing. Yeah, so on that note, at what point is it too late? How much time do you think we have? Well, the UN has now said, I think, revised their recent report and said we have to start a concerted global effort by 2020. I think that's next year. So if we do that and if we can reduce the emissions in their sort of benign a range of global greenhouse like gases, we can certainly avoid the calamitous increases of temperature, say, of three degrees centigrade, and hopefully level off around that. That's going to be bad enough. I mean, they pointed out

1.5 degrees centigrade has been very devastating to humans and the natural world. And we were thinking, well, wait a second, you know, the Kia rainforest is at two degrees centigrade, and Mexico was almost 2.5 degrees centigrade. And yes, the impacts on the natural ecosystems are truly calamitous. So we are, I think we're just, my distinct feeling now is we're headed quickly towards a point of no return, and we've got to start mobilizing. I'm not sure most people, well, the majority of people the United States do think climate warming is a major problem, but I don't think they sense any place that I've been, they sense the urgency of what we're facing. Now, you've talked about these big things that we need to address, climate warming, overpopulation,

how we're doing agriculture and all of that. And you mentioned that on a local level we can protect areas that have, you know, big variation in topography to allow insects to be. be able to move around, maybe move to higher climates in order to survive. Is there anything else that we can do like that that's on more local levels? Small scale changes that might be a little bit easier to start with? Well, yeah, I mean, most of the world is human-dominated in terms of, especially in terms of sort of patches of formerly natural landscapes, but still, you know, not totally decimated, inserted into a human-dominated landscape.

And I think the more locally that we can create, for example, I know around where I live in Western Mass, they have had since the past 20 years, they have been allowing the median strips to just go, not mowing them, but just let them flower to help with the insects and their food and breeding. So just local efforts like that, local efforts to perhaps preserve land, to make land off limits from, from, from. more so than they're doing now by zoning laws would help tremendously, I think, to at least give the insects a chance to have the habitat that's optimal for them to have a range of temperatures where they hopefully will seek a microclimate where they can survive. So I think there's much to be done at the local level. Yeah, and so on a very personal level in the urban areas that most of us live at, And what can we do in our own gardens or in our own cities in order to help replenish those insect populations?

Well, I know there are movements in New York City, for example, for more and more rooftop gardens, for more and more planters on what do they call them, not porches, not porches in the city. But you know what I'm talking about, little balconies. And that, you know, it seems like in a city of, I don't know how many people in London now, is it 10 or 12 million? Any big city, Beijing, London, New York, you know, the collective impact that we could have by some of these, you know, just very straightforward, not very costly initiatives, I think would be tremendous. There was an article recently that said that actually bees and pollinators are doing better in cities. where they perhaps, maybe they're free from pesticides, maybe they're free from predators,

but they're doing quite well, thank you. So the more we can facilitate that and perhaps have cities as the reservoirs and refusia for at least some pollinators, bees in particular, we can make an impact. So like you just said, it's going to take a concerted global and effort on the parts of many different organizations and people to really deal with what we're facing.

It's a daunting prospect, but we're fast approaching a point of no return. And once we hit a certain level of population collapse, not just for the insects, but for everything connected to the insects, the whole systems, the other thing people don't realize that we don't have systems thinking as a core part of educational system. I think it's a crime and we cut to do better. But everything is connected to everything else. And whatever we do to that web of life, we're going to do to ourselves.

And that's a message that many more people have to understand. That was Professor Brad Lister talking about his research into declining tropical insect populations. In the latest issue of BBC Focus magazine, we look into China's Changi Four Lunar Mission and ask whether this is the start of a new space race. We're also examining a bizarre condition called Afantasia, in which sufferers can't imagine things with their mind's eye and investigate where their accents are dying out. As always, there's much, much more inside. And remember, if you like what you hear, then please rate, review and share with anybody

you think might enjoy our podcast. You can also subscribe and leave us a review on your favourite podcast apps. Also, if there's anybody you'd like us to speak to or a topic you want us to cover, then let us know on Twitter at Science Focus. Thank you for listening to the Science Focus podcast from the BBC Focus magazine team. We're the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at sciencefocus.com or look out for us in your app store. This podcast is sponsored by Name, Audio and Focal.

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