Instant Genius - The decline of the insects, with Prof Dave Goulson

Episode Date: August 29, 2021

Entomologist Dave Goulson is the author of Silent Earth: Averting the Insect Apocalypse. He tells us how we can save the bugs and why they’re so important. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: sciencefocus.com Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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digital precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name audio.com to learn more. Hello and welcome to instant genius, a bite-sized master class in podcast form. I'm Alice Lipscomb Southwell, managing editor at BBC Science Focus magazine. In this episode, I talked to Professor Dave Goulson, an entomologist, at the University of Sussex. He's the author of the new book, Silent Earth, Averting the Insect Apocalypse. He tells me everything I need to know

about why insects are declining and how we can stop it. Hi Dave, so just to start, please could you tell us a little bit about yourself? Sure. So my name's Dave Goulson. I'm a professor of biology at the University of Sussex. And I've been sort of obsessed by insects all my life, I suppose, since I was five or six years old. I've no idea why, but I've been lucky enough to make a career

out of it, and I spent the last nearly 30 years specialising on bumblebees, which are my kind specialist subject, but I dabble in other insects too. Now, why are insects important? What roles in the ecosystem do they play? So many, it's hard to know where to start. I mean, insects are, so they make up the bulk of life on earth in terms of biodiversity, more than two-thirds of all species that we've identified are insects, and there are probably a lot more that we haven't identified. They're food for an awful lot of the other organisms. So, for example, birds, most birds eat insects, as do bats, lots of small mammals, lizards, freshwater fish like trout and salmon. They all depend on insects, so if the insects weren't there, they wouldn't be there.

But then they do a whole bunch of other important stuff. Scientists call it ecosystem services, is a bit of an unhelpful phrase I sometimes think. But anyway, things like recycling. So maggots help to get rid of dead bodies and dung beetles help to get rid of cowpats. And they help to break down dead trees and leaves and all sorts of other things. And so they're really important in nutrient cycles. They keep the soil healthy. They move seeds around. They do all sorts of stuff. I mean, I guess the thing that most people recognize is they pollinate. So roughly 87% of all the plant species on the planet need pollinating by some kind of animal. And occasionally in the tropics, that animal is a hummingbird or a bat, but 99% of the time it's some

kind of insect. So the majority of the world's plants would disappear without insects, including three quarters of the crops we grow would be affected without, you know, they depend upon insect pollination. So essentially life on earth would grind to a halt if we didn't have insects. And your new book that's just come out is called Silent Earth, and that's all about the insect apocalypse and how many insects are dying out. So why exactly are they dying out? So the drivers are many.

there's no single cause of insect declines. Probably the biggest one has been loss of insect-rich habitats in the UK, things like our ancient woodlands and heathlands and our fens and marshes, our flower-rich meadows. Most of them have been swept away. And obviously, this is not something confined to the UK and the tropics we've got deforestation, so on. Essentially, we're replacing natural, biodiverse habitats with. with either cities or monocultures of crops, and that's had a huge impact.

And actually associated with that is probably the second biggest driver of insect declines, which is the rise of pesticides and the many different pesticides we use in farming, but also in gardens and in our streets and, in fact, almost everywhere these days. But then there's a whole bunch of other things impacting invasive species, climate change, light pollution effects, nocturnal moths, and so on and so on. So it's almost like a sort of perfect storm. Insects might cope with one or two things, but they can't cope with this whole kind of blizzard of different adverse pressures on their populations. How do we know insects are dying out? Do you do surveys and see how many there are? It's actually pretty difficult to measure

insect populations in a consistent way, because there are so many of them, so many different ones, So actually the data we have are really patchy. The majority of insects we have no data for in terms of numbers of species. But there are some long-term studies of particular insect groups or in particular places using all sorts of different methods. And the ones we have, the data we have all kind of point in the same direction. They all, sadly, almost all, show patterns of decline. So just to give you a few examples, in the UK, we have a really.

good butterfly monitoring scheme, which has been going since the late 1970s, which is based on volunteers walking the same walk every fortnight through the spring and summer and counting and identifying all the butterflies they see. And that shows that British butterflies have fallen roughly on average by about 50% since 1976. There was a big study from Germany using kind of insect traps that catch flying insects that found a much bigger decline. There, they recorded a 76% drop in the weight of insects over a 26-year period. One estimate from the Netherlands suggests that butterflies there have declined by 84% since the beginning of the 20th century. So these declines have probably been going on for a long time. And just one other line of evidence,

while I'm at it. We've noticed that the insect-eating birds in particular have declined more than other birds. So, for example, cuckoos are down by more than 70% since the late 60s. Spotted flycatcher, which is a lovely little bird that I remember being common when I was a kid. Its populations have fallen by 93% in the UK. And it's a specialist on feeding on flying insects, as you might imagine from the name, flycatcher. And there's just not many flies for it to catch these. days, sadly. I mean, they're big declines as well, aren't they? I mean, any decline is bad, but it's not five or ten percent we're talking about, you know, like 70, 80 percent. That's just extortionate. That's huge. Yeah, it's really terrifying, especially given that it's probably

not the whole picture. You know, these declines have probably been going on for 100 years. And most of the data we have just relates to the last 30, 40 years. So exactly how many insects we've lost, we don't really know, but it's probably a big proportion. I mean, as you speak about it in the book, and I've considered it myself as well, but I remember when I was young, and you go out for a car drive, and there'd be bug splats all over the windscreen.

And just these days, I mean, admittedly, I live in a city now, but even when you go out in the countryside, you just don't get those bug splats anymore. No, it's interesting. I've heard this from so many people, and it's the only aspect of insect declines that is really, I think, kind of, impinged on the public kind of consciousness.

People don't pay much attention to insects. They mostly don't like them. If something comes near them, their first reaction is usually to swat it. So most people aren't kind of regularly looking at insects, but they cause this phenomenon of having to stop to clean your windscreen, which I can remember from when I was younger. And I think almost everybody that's old enough can remember, exactly when it ended is a bit woolly and, you know, I'm not entirely sure, but it's certainly true that, you know, there was a time a few decades ago where, you know, not just the windscreen, but the, you know, the headlights would get covered, the whole grill. The whole front of the car was, unfortunately, this massive, dried, splattered insect guts. And it just doesn't happen at all anymore. There is an interesting theory that it might be related to the aerodynamics of cars.

because obviously cars are more streamlined than they used to be. And that seemed to be quite a plausible, or at least partial explanation. So Kent Wildlife Trust did a study where they recruited volunteers with different aged cars to record the number of splats on them. And actually they found that even people driving around in classic cars that are much less aerodynamic, they don't have any splats on their windscreens either. So that isn't the explanation, it turns out, sadly. Oh, that's a shame.

I was hopeful then thinking, thinking, oh, maybe it's just owned up the cards, but yeah, if it is genuinely the decline. So are we seeing these declines all over the world, or is it just concentrated in certain areas or countries? That's a really good question, and actually the answer is the data we have, the long-term insect studies are really biased towards Europe and North America, where there are lots of scientists like me that are interested in insects. We have almost no data from, so Africa and South America and most of Southeast Asia. which is really worrying because that's where most insect, well, not just insect, where most biodiversity

lives. There were one or two studies from the tropics which show insect declines and pretty big ones, but for most tropical insects, we haven't really got any data. I'd be pretty confident that they're declining there too, because of course we're seeing, you know, massive habitat loss and climate change and all these other environmental issues affecting those countries as much or more than than places like Britain. But the honest. truth is, you know, we're really short on good studies from the tropics. So what will happen if we lose our insects? What will the future look like? Well, life will be tough, you know. I mean, the most obvious thing is, is pollination.

You know, most of the fruits and veg we eat, they depend upon insects to give a good harvest. And so, you know, if we lose pollinators, then it's going to be really difficult to provide a healthy diet. to the growing human population. But it isn't just pollination. You know, I mentioned earlier that insects help to keep the soil healthy, and we have major problems with soil degradation around the world. You know, soil health depends upon all the little creatures that live in it, and we need healthy soils to grow crops.

And we also need insects to recycle, you know, things like cow dung. It's absolutely vital that that gets all the nutrients in it, get recycled and there's actually a really interesting example of the importance of that. So when we colonised Australia and we took cattle to Australia, there were no dung beetles in Australia that can cope with cow dung. It's too wet. They're used to marsupial dung, which is really dry. And the poor Australian dung beetles drowned if they tried to do anything with cowpats. So the cowpats weren't being removed and they were just drying as like little sort of hard plates all over the landscape and eventually the entire landscape was covered in a layer of

cow pads and the grass couldn't grow through. At one stage there were 50,000 square kilometres of Australia covered under dry cow pads and so they introduced dung beetles able to cope with cow dung and it was one example of a very successful introduction some have gone badly wrong but they introduced dung beetles ate all the dung and now the cows are thriving the grass is doing well the nutrients are being recycled, to everyone is happy, well, almost. So it just shows that, you know, we take it for granted that the insects are there and they're doing these things. And if they're not there, then that's when we notice the problems. I think it's an interesting case study because you hear a lot, don't you, about introduced insects

or other animals and how they cause just huge problems. And then the plucky dung beetle he's done a good job. So that's really interesting. Yeah, yeah. I mean, there have been some disasters where, you know, I mean, any number of them one could mention. Many of them in Australia, actually, I mean, things like rabbits and cane toads and so on. We have Asian hornets invading Europe at the moment, which is a real problem because they love to eat honeybees, sadly. But just occasionally, we get it right, and an introduction has proved to be very useful. Speaking of introductions, because you say about honeybees, and am I correct in thinking that honey bees were originally from Europe, but they've been shipped all over the world to help with

pollination. So are they then causing problems in those new areas, maybe out-competing native bees? Yeah, they are, to some extent. So the honeybees native to Europe and Africa, there are other species of honeybees that are found in Asia, but the one that's been domesticated, and we have taken, as apis, molyphra is the scientific name of the sort of European honeybee. There now probably the most widespread insect on the planet. We've taken them to literally every country. Antarctica is the only place where there aren't any honeybees. And it has created problems. I mean, there are really two issues. One is that they, if there are lots of honeybee hives in an area, they take most of the pollen and nectar from the flowers. And that means that native pollinating

insects don't have much food left, which is obviously particularly a problem in areas which have been depleted of many of their flowers by other things that we've done. And there's a second less well-known problem, which is that we've accidentally spread lots of honeybee diseases and parasites around the world. And many of them will happily also infect wild insects like bumblebees. So, for example, there's a kind of Asian bee diarrhea called Nassima Serrani, a gut parasite of bees, which has accidentally come with honey bees to Europe. And is now quite common in wild bumblebee's humble bees in the UK and it often kills them. But that, you know, came with honeybees, sadly. So, yeah, we ought to be more careful where we put honeybees and how much we ship them around because

it has created a lot of problems. Is there an insect that is most under threat? I mean, there are lots that are acutely endangered. Maybe just, if I just had to pick one, there's these amazing things called Weta, which are giant crickets that live in New Zealand. And they basically fill the role of small rodents because there weren't any naturally in New Zealand. So they behave like kind of mice or voles. And they're great big, heavy insects amongst the biggest insects in the world. But they're easy prey for rats and introduced predators in New Zealand. And they're they only survive on one or two little islands off the coast. So that's one example of an acutely endangered insect. But of course, you know, there are many more.

I did meet her wetter. When I went to New Zealand a couple of years ago, there's this great place in Wellington called Zealandia, where they're trying to bring back all these native species and get it back to how it would have been before humans arrived at New Zealand. And they've got Chitara there, they've got wetter, they've got all these amazing birds. And they're so cool. They're massive, these wetter. They're really awesome. Yeah, they're very amazing. They're like kind of little insect tanks, aren't they? Extraordinary things. Very cute. So if there are a lot of insects under threat, then should we be eating them? Because there's

discussions at the moment saying how great it is for our health. You know, they're considered perhaps a more ethical way to eat. They're really high protein. You can keep them in. They don't take up as much space as cows or sheep or whatever. So if we ate them, might that help? Well, yeah, so I guess that we need to distinguish between breeding insects, cultivating insects to eat and catching them in the wild, you know, because the wild insects are declining, it's probably not a good idea that we start, you know, catching insects from the environment and eating them. But the idea of farming insects to eat is seems to have merit. Of course it's, you know, in the Western world, it's kind of not part of our culture to eat insects. And most people are quite squeamish about the idea that

it really fancy snacking on a plate full of cockroaches or whatever. But you're right, you know, they are very efficient at converting plant material into nutritious animal protein that we can digest easily. And they can eat, some insects can eat material that would be completely useless as a human food. So, you know, cultivating mealworms or crickets or whatever has advantages. You know, it's, it's, it, as you say, it takes them much less space than keeping cows or even chickens. They use much less water. And so, you know, perhaps we should. should be considering this as one kind of option in the mix of, you know, obviously there are one of the, I mean, arguably amongst the biggest challenges facing people is how do we feed

our growing population without doing terrible damage to the environment and maybe eating crickets and other insects is part of the solution. You said that there's some of the data's a bit patchy for around the world with population sizes of insects. Have we got any ideas of how many insects are still out there waiting to be discovered? Yeah, this is, this is interesting. So we've named 1.1 million species of insect so far, roughly, and people have tried to, I mean, we find new ones every day. There are undoubtedly lots we haven't yet described, haven't given any kind of name to. But scientists struggle to estimate exactly how many there are, you know, how can we know how many things there are that we haven't found, you know, it's, but people have tried to estimate and,

And most of the predictions suggest that somewhere between one and ten millions more insects that we haven't named. Obviously, that's a huge kind of, you know, range. Probably somewhere in the middle is probably most realistic, four or five million more. But that's, I mean, that means that we've only named about 20%. Which is absolutely astonishing that there are all these amazing creatures out there that we've yet to discover. I think that's kind of, you know, jaw-dropping and really inspiring. Is it likely that any of them could be in our back gardens, or they're more likely to be out in deserts or jungles where it's quite inaccessible for us?

Yeah, well, actually, it's really easy to catch a species that no one has described before. I mean, certainly there are many more in the tropics than you would be hard pushed to find one in your garden, although it's not impossible. The difficulty is knowing it's a new species. So, you know, if you swish a net around in a tropical forest, you'll catch hundreds of insects, and probably many of them would be new to science. But knowing which ones those are, it's an incredibly specialist job. It requires, you'd basically have to take that little fly or whatever it was to the world expert

on that particular family of flies who might be in a museum in Europe or North America and have to persuade them to spend several hours staring down a microscope at this little fly trying to work out, is it one of the ones we've already named, or is it something different? So it's really specialist and there are so few experts able to do it that really limits how fast new species can be found. But there could be what some in our, you know, there will undoubtedly be some in the UK, but they're probably very similar to species we have described. So, you know, it would be hard to distinguish them. And, you know, they're probably there. So if you know, if you want to start looking, go for it.

Ever the optimist, I'll be out there with my net and in the pond. Actually, interestingly, there was a new species of butterfly discovered quite recently in Ireland, a wood white butterfly, which is very similar to the wood white butterfly. We knew it was already here, but nobody had noticed, and it presumably always been there. But butterflies are incredibly well studied. So the idea that there's been a, there was a butterfly species right under our noses that no one, even knew was there, is pretty cool. Yeah, it was three or four years ago now. It was discovered. But yeah, you know, so there is hope. Anyone could find a new species. You've got to just be eagle-eyed enough. Just earlier we talked about honeybees and how important they are for pollination.

There is a fact you hear a lot that one third of our food is pollinated by honeybees. So is this true or is that maybe, you know, a bit optimistic? So roughly, 75% of the crops we grow are at least partly dependent on insect pollination. So three quarters, which we're, you know, and it's most of the fruit and veg. But actually those three quarters of our crops only provide about 30% of our food by weight because the 25% of crops that aren't insect pollinated happen to be that they're wind pollinated. They happen to be the world's biggest crops, things like wheat and rice and corn and so on, the grasses that are all wind pollinated. So that's where the 30% figure comes from, but it's slightly misleading because many of those

crops, things like apples, you will still get some apples without any pollinators. You just don't get as many and the apples don't tend to be as big. So it's not that we would lose all of that 30% of our food. It would be somewhat less than that. And probably the most realistic estimate I've seen is actually that it's probably about 10% of our food by weight that would be gone if we didn't have insect pollinators. But even so, you know, if you took away 10% of the world's food supply, that would obviously create enormous problems. So is there anything we can do in our day-to-day lives to help the insects, if they are in decline, well, as they are in decline? One of the nice things here is that we can all help.

You know, lots of these environmental kind of stories or issues, you know, you feel helpless and it's depressing and, you know, you see the rainforest burning on the news and all this kind of terrible things happening and you feel like, well, you know, what on earth can I do to help? But with insects, it's different and I think it's really nice that, you know, because they do live all around us, they live in our gardens and local parks and in the road verges and, you know, they're everywhere. And so even small things that we do really do make a difference. And most insects, thankfully, haven't yet gone extinct.

And they can breed really fast. So if you provide the right conditions for them, their populations recover really quickly, you know, unlike pandas or tigers or whatever. So, you know, the obvious place to start, if you're lucky enough to have a garden, is that actually it's really easy to increase the number and diversity of insects in your garden

just by taking some really simple steps. I've written books about this. The garden jungle and gardening for bumblebee are both basically how to increase diversity in your garden. Or if people don't want to buy a book, then my YouTube site's got lots of advice as well. But grow lots of bee-friendly, pollinator-friendly flowers, grow some wildflowers.

Don't know your lawn too much. Flowering trees, if you've got a big enough garden, are great. Have a pond, which will support a whole range. of insect life. A little bee hotel. They work quite well for some solitary bees. Don't use any pesticides. I'm actually running a campaign at the moment asking people to sign. It's one of these government petitions calling for a ban on urban pesticide use, which is actually following what the French did a couple of years ago. It seems crazy to me that we spray poisons in our gardens and that the

council spray them in our streets and so on. But, you know, they're really simple things and many of them involved doing less rather than more, you know, less mowing of your lawn, less spraying of pesticides, not being so tidy, allowing a few weeds to flower. And it really does make a difference. And I mean, there's an amazing example of how much life you can attract to a garden from Leicester, which is not known as a biodiversity hotspot. I think it's fair to say, no offence to Lester. But there was a lady there called Jenny Owen, who lived close to the middle of the city. She had a little garden of about an eighth of an acre, so, you know, nothing special. But she, she garden for wildlife, and she spent 35 years trying to identify and catalogue every species of animal and plant

she could find in her little garden. And I mean, incredible effort, you know, half a lifetime. But it's extraordinary, her grand total was 2,673 different species of animal and plant in her little garden, of which, if I remember correctly, 1,997 were insects, different species of insects. So, I mean, it sounds like the sorts of figures you'd expect from a rainforest, you know, thousands of species living in a garden. So really simple things we do could really help. And there are 22 million private gardens in the UK. So just imagine if, you know, most of them were insect-friendly, wildlife-friendly, that would

really make a difference. It would be kind of like a, you know, a national network of little patches of little miniature nature reserves. I think that would be fantastic. It's getting away from that idea, isn't it, of your garden must be this all perfectly flat green lawn and everything has to be perfectly manicured and just, you know, be a bit lazy, a little, go a bit wild, and then all the insects will come back and it's a great habitat for them. Yeah, and people are, it is happening. You know, it's really exciting that lots of people are sort of making their gardens more wildlife-friendly. And perceptions of changing, it's slow. And, you know, there are still people that want to have a kind of stripy, like a Wimbledon tennis court lawn in their garden. But there are a growing number of people that, you know, prefer to have a shaggy lawn with lots of flowers in it. And, you know, I hope that that will spread and spread. And eventually, you know, that will become the norm, the new norm. And that, as I say, would really make a difference. So finally, just to wrap up on this then, so what are three things that our listeners really need to know about insects?

So there's so much I could have gone for. I could have gone for some obscure kind of, you know, facts, intriguing facts about insects or whatever, but I'll stick to the important stuff as far as I see it. So, I mean, firstly, we all depend upon insects. You know, love them or load them. Insects are vital to life on earth, including us. our lives would be much, much harder without them. So number two then is that, I mean, insects of, they were among the first creatures on land. They've been around for 400 million years, much, much longer than we have. And for almost all that time, they were the dominant life on Earth. You know, if an alien had peered down at our planet anytime in the last 400 million years, they would have thought this was the planet of the insects. And it's only very recently that

that started to change and that we've taken over. And now these insects that have survived mass extinction events and everything else. They're now, they're in trouble, and it's down to us. And then so, I mean, number three, I think the most important thing is we can all help. You know, we can all get involved. We can do things. Make your garden more insect-friendly. Even flowers in a window box will help.

Vote with your pocket when you buy food, buy organic food, buy locally produced, seasonal produce, eat less meat. That all reduces our impact on the environment. And one way or another helps the insects. So the third thing is most important. important, you know, get involved, do something to help the insect. Thank you for listening to this episode of Instant Genius. That was Professor Dave Goulson.

If you want to know even more about the insect apocalypse, check out his book Silent Earth, which is available now. Or, to hear even more from him, head over to the Instant Genius Extra Podcast now. The latest issue of BBC Science Focus magazine is out now. Pick up a copy in store or visit ScienceFocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analogue warmth.

Alongside French acoustic specialist Focal, Name creates high-end audio systems combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at Name Audio.com.