The extraordinary lives of insects are changing; the ecosystems on Earth have altered more rapidly in the past hundred years than at any previous time in human history. Well over half of the planet’s land area has been transformed through agriculture, livestock grazing and construction. And the pace is increasing. This means that habitats are being lost and those that remain are being divided into small, isolated fragments. Dams and artificial irrigation are putting the planet’s freshwater resources under ever-increasing pressure. We have produced and thrown away so much plastic that we will be finding vestiges of it in the sediments in the form of microplastic for generations to come. Every year, we produce substantial amounts of chemicals, including the pesticides we use to protect our crops, which in turn kill insects. We displace species, both intentionally and unintentionally. We have doubled the amount of nitrogen and phosphorus in the soil through the use of artificial fertiliser, and CO2 emissions are higher than they have been for tens of millions of years, contributing to climate change.
All of this affects insects – and anything that affects insects affects us. Indeed, a decline in the number of insects and the extinction of species will spread through the ecosystem in a ripple effect with major consequences over time because of the impact on so many fundamental ecological functions. Fortunately, we’ll never manage to wipe out all the bugs, but we would do well to take more care of our tiny, six-legged, winged friends, because despite their 479-million-year track record, they’re starting to struggle.
We only know of a tiny proportion of all the insect species in existence, and we have little solid monitoring data about those we do know of. Even so, one estimate indicates that a quarter of all insects may be under threat of extinction.
One important point in this connection: it’s too late to worry when a species is on the brink of extinction. Species cease to function in the ecosystem long before the last individual dies out. That is why it is so vital not to focus exclusively on species extinction, but also to turn the spotlight on the decline in the number of individuals, and there is much to suggest that insects are becoming fewer. In Germany, the accumulated biomass of all insects trapped in more than 60 locations nationwide has plummeted 75 per cent in just 30 years. Global data suggests that while we humans have doubled our population in the past 40 years, the number of insects has been reduced by almost half – these are dramatic figures.
So, why are insect numbers falling? It’s not so easy to say because there are almost certainly many connected causes. Important factors include increasing land use, intensive farming and forestry practices, pesticides and the decline in natural remnant habitats, as well as climate change.
What happens when our demands for constant growth in the use of land and resources cause insect populations to crash, species to disappear and insect communities to change? Think of the world as a hammock made of woven fabric: all the species on the planet and their lives form part of the weaving and all of them combined create the hammock we humans are resting in. Insects are so numerous that they account for a large share of the hammock’s fabric. If we reduce insect populations and wipe out insect species, it’s as if we are pulling threads out of this weaving. That might be fine as long as there are only a few small holes and loose threads here and there, but if we pull out too many threads, the whole hammock will eventually unravel – and our welfare and wellbeing along with it.
Overly drastic changes in insect communities can have domino effects with consequences nobody can predict. Indeed, we do not know what their significance might be – only that things may become very different. We risk living in a world where we humans face a tougher existence because the challenges of assuring clean water, sufficient food and good health for all become even greater than they are today.
In conclusion, let’s look at a few challenges, some examples of the factors that threaten insect life, both locally and globally.
First, land use. This is undoubtedly the greatest threat. We are using land ever more intensively, which means fewer habitats and less intact rainforest in the tropics. Back home, fewer flower meadows in agricultural land and densely built-up areas, and fewer areas of natural forest, where old dead trees get to play out their role as housing estates for insect diversity. It also means more artificial light, which has an impact on many insects.
Second, climate change. Warmer, wetter, wilder – that’s the outlook. And what do these changes mean for insect life?
Third, challenges related to the use of pesticides and new genetic manipulation techniques. A vast field that leaves us with more questions than answers.
Fourth, and finally, the introduction of non-native species and their effect on bugs. What is the right way of dealing with ‘past sins’ in this area? Is it possible to reverse them and is this the correct prioritisation? Because at the same time as we wipe out species, the changes we make also create room on the planet for new species, brought to the fore by the thrust of evolution. How robust is nature and how shall we weigh up concern for our own kind against concern for millions of other species?
The Frog You Wouldn’t Want to Kiss
In the South American jungle lives a poisonous frog with the thoroughly appropriate Latin name of Phyllobates terribilis. In English, it goes by the name of golden poison frog. This isn’t a frog you’d want to kiss in the hope of finding a handsome prince. If you tried, you’d be dead within minutes – guaranteed. The poison in question is one of the most powerful nerve poisons known to mankind, batrachotoxin. An average frog contains roughly 1 milligram of the poison – about the same weight as a grain of salt. This alone is enough to kill 10 grown men. And just so you know: there’s no antidote.
This little frog, no larger than a plum, used to be fairly common in the rainforest in parts of Colombia. The locals would carefully stroke their arrows along the frog’s back to ensure that their arrowhead was poisonous enough to kill anything they might encounter.
The pharmaceutical industry got wind of this shocking yellow poisonous sensation in the rainforest. Early tests indicated that the poison was an incredibly effective painkiller – in suitable doses. What’s more, because it affects the transportation of sodium through cell membranes, it could also be significant for our understanding of numerous diseases where this is important, such as multiple sclerosis (MS). A few specimens were fetched from the jungle for closer examination, but guess what happened to the catch when it arrived in the laboratory? The frog was no longer poisonous!
The fact is that nature is often craftier than we expect: the golden poison frog is not poisonous in itself, it only produces the poison while living in its natural habitat. Why? After much laborious detective work we now know that the poison comes from a diet of – yes, that’s right (this is a book about insects after all) – beetles! A beetle from the soft-winged flower beetle family, Melyridae, to be precise. So, the frog is only poisonous when it gets to eat the right kind of beetles in its natural forest habitat.
Thanks to rainforest logging the golden poison frog is now listed as threatened with extinction. A desperate battle to rescue the species is under way, but there are few bright spots. Not only is the frog’s habitat vanishing but the trade in frog legs has led to the spread of a fungal disease (popularly known as Bd), which is killing frogs, toads and newts across the globe. A third of them are now on the point of vanishing for good. Soon there will no longer be any golden poison frogs and no opportunity to do further research into the active ingredients they produce.
Varied Landscapes Increase Insect Numbers
If we want to preserve our chances of seeking out active medical ingredients, we need to take care of the habitats of these species. Conserving natural areas intact is one important means of securing habitats, both in the rainforest and here in Europe. Many specialised insects have such peculiar, special needs when it comes to where they can live that they cannot survive in a totally transformed modern landscape. This means that nature reserves and other conservation areas are crucial if we are to safeguard unique species. But it is also important to retain as much of the variation seen in the natural landscape in places outside the large conservation areas too. In the forest, that may mean ensuring there are enough old trees and dead trees. Because dead wood plays a central role in a living forest (see here), housing a large share of forest species, including insects – which make themselves useful as decomposers, pollinators, dispersers of seeds, as food for other animals and as pest controllers. And although many European countries have recently launched initiatives to increase the amount of dead wood, the volumes are still low compared to natural conditions.
In our farmland and cities we can also achieve a great deal through simple measures that simultaneously serve to beautify the environment for us humans: a belt of trees and bushes alongside a stream in a residential area; verge- and hedgerow-cutting along the roads and a border of wild-flower meadow along the edge of a field; a patch of uncultivated land in the middle of a field with old hollow oak trees. A varied landscape offers many more opportunities for complex insect life. Again, this benefits the pollination of both wild flowers and our crop plants. Because honeybees, wild bees and bumblebees aren’t the only insects required for good and efficient pollination. This is high-level teamwork involving many players. It is often the case that flies, beetles, ants, wasps and butterflies are less efficient pollinators per flower visit than bees and bumblebees, yet this is frequently offset by the fact that they visit many more flowers overall because there are a heck of a lot of them. Some of these ‘non-bees’ may also have peculiar habits and adaptations that benefit effective pollination.
If we combine data from a few dozen research projects from five continents about crops of, say, rape, watermelon, mangoes, strawberries, and apples, we find that the plants produced better crops (an increased fruit set) when they received visits from ‘non-bees’ regardless of how many bees paid them a visit. It seems that these other insects contribute something unique, something that bees cannot deliver. There are also differences in how vulnerable the different insects are to changes in the landscape, which is an advantage for our food production. In sum, all these insects operate as a kind of pollinator insurance: if one species can’t get the job done, another one can step in.
We know that intact species diversity can make the ecosystem more effective when it comes to capturing resources, such as water and nutrients, and this results in more biomass. That knowledge is key once we grasp that this biomass is precisely what serves as the basis for crops, and the food that ends up on our dinner table. We also know that species diversity is central to breaking down the biomass once again and thereby ensuring that the nutrients are released, which enables new production.
What’s more, we are gaining increasing support for the notion that intact biological diversity can make ecosystems more stable over time than impoverished diversity. There are many mechanisms in play, including the fact that different species have different strengths. One species grows best during cool summers, while another shines beneath a baking summer sun. When species decline or are wiped out, nature has fewer variants to play with and we are more poorly armed against both natural fluctuations and man-made changes – in the climate, for example.
It’s not easy to put a price on the services insects provide, although that hasn’t stopped people from trying. For example, the annual global contribution of the many pollinating insects is estimated to be worth around $US 577 billion – equivalent to a little under two-thirds of UK current revenue for 2015. Decomposition and soil formation are estimated to be worth four times as much as pollination in total. Although these figures vary depending on calculation methods and are pretty approximate, they still show that the contribution from insects is extremely valuable in pounds, shillings and pence, and it makes good economic sense to look after them.
Troublesome Light
The fact that we humans are spreading out over increasingly larger expanses of the planet also has some consequences we don’t think about on a day-to-day basis, such as light pollution – the sum of artificial outdoor light produced by streetlamps, houses, holiday cottages and industrial buildings. Light pollution is currently growing at a rate of 6 per cent per year and is disturbing our ecosystems, including insects.
We all know that moths are attracted to light, although the exact cause is a matter of debate. According to the leading theory, they think the light is the moon and try to orientate themselves by maintaining a fixed angle to it. While this works perfectly well with the moon, which is an awfully long way off, the result in this case is that they spiral in towards the artificial light and generally end up getting fried.
Street lighting can alter the local species composition of bugs. When artificial light is reflected off shiny surfaces, this can also confuse land-living insects that lay their eggs in water. Where we see a parked car beneath a streetlight, a dragonfly simply perceives the light as being reflected off the surface of a body of water, and drops its entire life’s egg production in the wrong place.
And what happens to insects over the long term? Could light pollution cause urban insects to change their behaviour and avoid light, for example? To test this, some Swiss scientists compared 1,000 larvae of the spindle ermine moth species (Yponomeuta cagnagella), half of which came from the city and half from the countryside. All got to spend their childhood in similar lighting conditions in a laboratory. Right after hatching, as night fell, they were let out into a large net cage, with a light source placed on the opposite side. Then it was just a matter of waiting the whole night through.
Would city moths and country moths be equally attracted to the light?
The result was clear: city moths were evidently much less attracted to light, by an average of as much as 30 per cent. This indicates that nocturnal moths that have spent generation after generation living in an artificially lit environment have undergone an evolutionary adaptation to artificial light. After all, it doesn’t make much sense for masses of them to fly round and round streetlamps, getting burnt or eaten up by predators that have worked out where the buffet is being served. This could explain the emergence of selective pressure against attraction to light among urban moths.
On the one hand, this is fine, because it prevents them from dying like that. On the other, it can have far-reaching adverse consequences. Because there is a cost attached: the avoidance of light probably means that urban moths simply spend more time sitting still.
Consequently, the effect of artificial light in built-up areas alters the insects’ role in the ecosystem. For example, it is difficult for nocturnal insect-eaters to catch an insect that is hidden and motionless. Nor is an insect that can’t be bothered to fly going to get much pollination done among flowers adapted to nocturnally active pollinators. That is why it is important to restrict light pollution and, in particular, to try and keep artificial light away from natural areas not yet affected by it.
Warmer, Wetter, Wilder – What About the Beetles?
We know that we are heading towards a future in which the climate will be different. This will also affect insects, both directly and indirectly.
One challenge is that climate changes disturb the finely tuned synchronisations between different species. We see a shift in the timing of many processes, such as the return of migratory birds, and foliation, or spring blossoming. The challenge is that different events do not necessarily shift in sync. If the insect-eating birds produce their young too late or too early in relation to the period when there are most insects, there may be too little food for the chicks in the nest. This can happen if some events are triggered by day length (which is not affected by global warming), while others are triggered by mean temperature, for instance. In the same way, plants that are reliant on particular insects for pollination may suffer poor seed production if they flower at a point when these insects are no longer swarming.
The spring can be particularly challenging, especially ‘false springs’, which arrive far too early. When that happens, overwintering adult insects are tempted out by the warmth and go in search of food. When the frost returns, the insects will struggle to cope with the cold and with finding enough food because they have poor cold tolerance and few food reserves in the spring.
We see that many insects try to adapt in response to changes in the climate. Sometimes their entire distribution is shifted, but we often see that the species fail to keep up and the distribution shrinks instead. In the case of dragonflies and butterflies, it has been proven that many species have become less widespread and are shifting northwards. Colour charts of the different dragonfly species show that many butterflies and dragonflies, especially those with dark colouring, have vanished from southern Europe and sought refuge in the Northeast, where the climate is cooler. Forecasts produced for bumblebees indicate that we may risk losing between a tenth and – in a worst-case scenario – half of our 69 European varieties by 2100 owing to climate change.
In the North, climate change is increasing the distribution of leaf-eating caterpillars. This also exacerbates the effects on the birch forests, which are being chewed bare. Over the course of a decade, outbreaks of autumnal moths and their relatives have caused considerable damage to the birch forests of Finnmark in northern Norway. The outbreaks have ripple effects on the entire system: food conditions, vegetation and animal life are all changed.
© Carim Nahaboo 2019
Along with researchers in Tromsø and at the Norwegian University of Life Sciences, I have looked at how the autumnal moths’ depredations affect a different group of insects: the beetles that break down the dead birches, thereby ensuring that the nutrients are recycled. Our results show that the attack of the autumnal moths creates so many dead birch trees in such a short space of time that the wood-living beetles are simply unable to keep pace. They cannot respond to the increase in available food with an equivalent increase in the number of individuals. We do not know what effect this may have over the long term, and this illustrates a key point: we have no idea what sort of consequences continued temperature increases will have for the ecosystem in the North, but it is obvious that there will be dramatic changes.
Since one of my research fields is insects in large, ancient and hollow oak trees, I have been wondering how climate change will affect the beetles inhabiting them. A couple of years ago, my research group and some Swedish scientists compared a large dataset that covered beetle communities associated with oak trees across the whole of southern Sweden and southern Norway. The oaks stood in places with differing climates, so that the range they spanned in terms of temperature and precipitation was roughly equivalent to the changes foreseen in climate scenarios. We used this to look at differences in the beetle communities in order to gain knowledge about how a warmer, wetter and wilder climate might affect these different insect communities in the future.
In our study, we found that warmer climates were good for the most specialised and peculiar species. Unfortunately, though, these unique species also reacted badly to increased precipitation. This means that climate change is hardly going to improve conditions for these particular insects. However, the more common species showed few reactions to climate in our study.
This confirms a pattern that is common in our times, not just in relation to climate changes but quite generally: locally unique, specially adapted species are the ones that suffer, whereas common species do fine. This means that many rare and unique species will go into decline, whereas relatively few species that are already common will become commoner still. This is known as ecological homogenisation: the same species are found everywhere and nature becomes more similar across different geographies.
Insecticides and Genetic Manipulation: Dare We, Should We?
Every year, we use massive amounts of chemicals quite intentionally, precisely in order to kill insects. After all, that’s the whole point of insecticides used in agriculture, and private homes and gardens.
Many people think the intensive use of pesticides in agriculture is a price we must pay to be able to feed a constantly increasing population through industrial agriculture. Others will argue we ought to take a more ecological approach and cooperate with nature in our agriculture practices, even if this might lead to lower crop yields.
Although we don’t have space to go into this discussion here, I must mention the large and growing documentation detailing the unwanted harmful effects of neonicotinoids, a widely used group of insecticides. These substances affect the navigation and immune defences of honeybees and wild bees, and may be among the reasons for the decline in these groups.
We humans have recently acquired a brand-new tool in our battle against insects that are harmful to us. I’m thinking of genetic manipulation, in particular what is somewhat cryptically known as the CRISPR/Cas9 Method. This is like a pair of molecular scissors that can cut up genes and may be used to alter an organism’s DNA by removing or exchanging certain genes. The method may be combined with something called a gene driver, which ensures that the genetic change rapidly spreads to pretty much all offspring.
Malaria is caused by a tiny parasite that the mosquito carries with it from one infected person to another when it sucks their blood. Every year, around half a million people die of malaria, most of whom are under five years of age. Even so, the numbers are much lower than they were just 15 years ago, and much of this decrease is down to simple measures, such as the use of insect nets impregnated with insecticide. But now we also have a tool that could ultimately be used to wipe out the malaria mosquito once and for all. This can be achieved by making one of the sexes sterile or by ensuring that all the offspring are the same sex.
This has prompted a timely question from the Norwegian Biotechnology Advisory Board in several different forums: dare we – and should we – use such tools in the natural world? We know little about the impact. One issue is that we don’t know what cascading effects this could have in the ecosystem. What if we eliminate one species and another simply steps in and takes over as a spreader of disease? For all we know, things could end up worse than they were to start off with.
Another question is whether the use of a tool like this could lead to undesirable mutations, with undreamt-of consequences. Terrifying scenarios, such as the spread of sterility to other organisms, lie in wait. Despite the need for haste, we must proceed with caution: before we start to use the new gene technology tools to genetically alter or wipe out insects that spread serious diseases we must protect ourselves as best we can against undesirable consequences.
The End of the Giant Bumblebees
We humans have changed a lot of things on this planet. Some are things we cannot change – like the fact that our forefathers already wiped out most of the really big animals, tens of thousands of years ago on continent after continent. Gone were the mammoth, the sabre-tooth tiger and the giant sloth. And along with them, a great many insects almost certainly died out too, insects associated with this megafauna in various ways, although we know even less about them.
Other changes are much more recent. Seagoing explorers brought cats, rats and other efficient predatory mammals to islands where life had gone its own way. Native species that hadn’t the wit to look after themselves, species developed in the absence of such enemies, were then often summarily dispatched.
We continue to displace species at a rapid pace, sometimes without meaning to, and sometimes quite intentionally. Like the import of buff-tailed bumblebees to South America, where they were supposed to improve pollination in fruit orchards and greenhouses. The buff-tailed bumblebee has spread rapidly and is crowding out the local giant bumblebee, Bombus dahlbomii, apparently because the buff-tailed bumblebee carries parasites that the giant bumblebee can’t cope with. The Bombus dahlbomii is the world’s biggest bumblebee, affectionately described by bumblebee expert Dave Goulson as ‘a monstrous fluffy ginger beast’. Soon it might be gone forever.
So, what are we to do with introduced species that threaten unique native species? These are big, difficult and important questions that we need to debate more in society. In some cases, the decision forces itself upon us, as in New Zealand. The government there has launched a plan to wipe out rats, opossums and stoats. These alien species kill roughly 25 million birds every year.
Many other island nations suffer from the same problem. This challenge can be illustrated by a tale from Australia about a once-extinct stick insect that was rediscovered, and the living, but soon-to-be dead black rats that ate it up.
Routing the Rats
On 15 June 1918 the steamship SS Makambo, packed to the gunwales with fruit and vegetables, ran aground just off Lord Howe Island, a tropical island far out in the Pacific Ocean. An easterly outpost of Australia, its few inhabitants were separated from the mainland by more than 600 kilometres. The important point about this shipwreck is the rats who managed to reach dry land. In the nine days it took to repair the ship, an unknown number of black rats managed to reach the shore and establish a foothold on the island.
For millions of years Lord Howe Island had lain isolated in the middle of the ocean. Unique species had developed there, species that existed nowhere else on Earth. But the rats hadn’t come to chill on the beach. Remember the story of the very hungry caterpillar (here)? The one that ate its way through an apple on Monday, two pears on Tuesday and ended up ploughing its way through oranges, sausages, ice-cream and chocolate cake before the weekend was over? That’s roughly what the rats did on Lord Howe, too, the only difference being that they ate up unique species, one by one. In the early years alone, they finished off at least five species of birds and thirteen small animals that couldn’t be found anywhere else in the world.
One of these small creatures was a gigantic stick insect. You know, those thin pale-brown insects that look like dried twigs. But this species wasn’t just any old stick insect. We’re talking about a quite special insect, the world’s heaviest stick insect: it was the size of a big barbecue sausage, dark, shiny and wingless, and aptly went by the nickname of ‘tree lobster’. Its Latin name, should you wish to know it, was Dryococelus australis. This insect proved to be a slap-up meal for hungry rats. By as early as 1920 the species was already declared extinct – a kind of belated victim of the shipwreck two years earlier.
But this story takes an unexpected turn. Because the outpost has an outpost: 20 kilometres away from Lord Howe Island lies Ball’s Pyramid, a sheer narrow sea stack almost twice the height of The Shard in London. For years, it attracted adventurous climbers, but since being awarded World Heritage status in 1982 (along with Lord Howe Island), only scientific expeditions have been allowed to visit. Around this time persistent rumours also began to circulate that there were ‘tree lobsters’ on the sea stack. And suddenly there was no end to the number of climbing expeditions with an inordinate interest in bugs that were applying for climbing permits to go looking for this rare stick insect. In the end, the man in charge got so sick of assessing climbing permits disguised as insect research that he decided to put an end to the rumours once and for all.
And so, in 2001, two scientists and two assistants travelled to the sea stack. They climbed up the sheer rock face without seeing a single tree lobster, but on their way down, they discovered a small bush of the type eaten by the insect, wedged into a crevice in the rock face. Below lay some large droppings, which looked fresh. Hard as they searched, not a single living stick was to be seen so there was only one thing left to do: repeat the climbing expedition at night – because the world’s largest stick insect is known to be nocturnal. Equipped with headlamps and cameras, the climbers experienced something akin to a waking dream. Unbelievably, there, in the middle of what was pretty much the sole bush on the entire stack, sat 24 huge black stick insects, staring at them.
Nobody can say how the insects made their way from Lord Howe Island to the sea stack some time before the extinction in 1920. If you can’t fly or swim, a 20-kilometre trip across the open sea is quite a challenge. The most likely explanation is that eggs or a pregnant female hitched a ride with a bird or on floating vegetation and then managed to survive for at least 80 years on the inhospitable sea stack that is almost entirely bare of vegetation.
We will draw a veil of silence over the bureaucracy that ensued. After two years of paper-shuffling, permission was finally obtained for two males and two females to be fetched from the sea stack to form the start of a breeding programme. Two of them (christened Adam and Eve, of course) survived by the skin of their teeth and healthy stocks of stick insects can now be found in several zoos, including Europe. But then the question arose of returning the rest of them to Lord Howe Island, where the species actually belonged. Because a sea stack with a single bush at the mercy of rock falls is hardly fit to be a permanent home for a viable population of stick insects living in the wild. But on Lord Howe, the black rats still prevail. Unless they are wiped out, there’s no point reintroducing the stick insects. And they aren’t the only creatures who would be glad to see the rats killed off: 13 bird species and two reptile species face extinction unless the rats are eliminated so the authorities now plan to do away with the rats once and for all. This requires extreme measures: 42 tonnes of poisoned cereal will be scattered over the island from a helicopter.
Of course, it isn’t entirely straightforward. First of all, animals other than the rats may die from eating the grain – including the birds that people are trying to rescue. So, the idea is to trap the most vulnerable bird species and keep them in a kind of temporary Noah’s Ark, then release them again after the poison rain. But what consequences will this have for the genetic diversity of the birds, for example – because it won’t be possible to capture all the individuals, will it?
And then some people are worried. There are only 350 human inhabitants on the island but not all of them are keen on being showered with poisoned breakfast cereal, even though the authorities have assured them that no poison will be scattered near houses. Some probably also think that the big black stick insects are repulsive and no more deserving of protection than the black rats. Because conservation biology is just as much about us humans and our thoughts and feelings as about the species we are trying to conserve.
New Times, New Species
In many ways, nature is robust and it is adapting all the time. New species emerge where we humans create new opportunities. Like deep below the ground in London, where the rough damp tunnels of the Tube are home to a highly unusual mosquito. It belongs to the Culex pipiens species, the most common type of blood-sucking mosquito found in urban areas, but has developed into a special genetic form (called molestus – ‘the troublesome one’), which is no longer capable of producing offspring with its mosquito relatives up in the light of day. What almost certainly happened is that a couple of female mosquitoes found their way down into the depths at some point many years ago, perhaps when the Tube was being built in 1863. And since then, the London Underground mosquito has lived its own life down there, over hundreds of mosquito generations.
The mosquito became notorious during the Second World War when it was a source of great irritation to people seeking shelter in the Underground system during the Blitz. Today, standards are far better than in those days and although roe deer, foxes, bats, woodpeckers, sparrow hawks, tortoises and great crested newts have all been spotted in the tunnels, rats and mice are the main species that keep the few London Underground mosquitoes company.
Genetic analyses have shown that the mosquitoes’ DNA varies between lines and stations: the Piccadilly Line mosquito is different from the Central Line mosquito – although not different enough to prevent the various Underground mosquitoes from mating with one another. The leading theory is therefore that all of them are descendants of the same bold forebears from 150 years ago.
If it is true that the mosquito has developed into a new genetic form in just 150 years, this is an example of how evolution can work quickly now and then – as when populations are living in total isolation. Charles Darwin envisaged that new species needed tens of thousands, if not hundreds of thousands of generations to come into being. It is odd to think that while he sat pondering this in his house on the outskirts of London – he had just published On the Origin of Species in 1859 – a process of lightning-fast evolution may perhaps have been starting beneath his feet.
We will probably see more such examples of new and rapid species formation in the future as a result of our intentional and unintentional displacement of species. The North American fly, Rhagoletis pomonella, used to live contentedly on hawthorn trees until apples came to the US from Europe. Now the fly has two different genetic forms – one that only eats hawthorn berries and another that only eats apples. In just a couple of hundred years, one species is well on its way to becoming two. Even the parasite that lives on this fly is in the process of splitting into two species, one for the hawthorn-eating and one for the apple-eating larva.
When new insects appear and others die out, the effect will depend on which species change. Because, as I have shown in this book, different insects perform different tasks in nature. What’s more, every single insect is connected to other species through ingeniously adapted interactions, and this is the basis for all the goods and services nature offers us.
We humans have long taken the free services of insects for granted. Through intensive land use, climate change, insecticides and invasive species, we now risk altering conditions so quickly that insects will have difficulty delivering as they have done to date, despite nature’s adaptability. On egotistical grounds alone, we should therefore be concerned about the health and wellbeing of these little critters. Taking care of them is a form of life insurance for our children and grandchildren.
If we could only stop navel-gazing for a second, we would see that this is about more than mere utility value. As far as we know, our planet is the only place in the universe where there is life. Many would say that we humans have a moral duty to rein in our dominance of the Earth and give our millions of fellow creatures a chance to live out their tiny, wonderful lives too.