'We cannot survive without insects'
Many people see insects as annoying pests. But British biologist Dave Goulson cautions: A world without insects is a dull place without coffee and chocolate — and with dead animals and cow patties piling up.
Deutsche Welle: How many insects are there in the world?
Dave Goulson: Insects are the dominant lifeform on the planet. We've named well over a million species of insects, and there could be 5 or 10 million. As for the number of individuals, it's safe to say that there are many more insects than anything else, excluding microorganisms like bacteria.
Why are insects disappearing?
Most people agree that it's a combination of factors, primarily associated with the way farming has changed in the last hundred years. We've moved to this kind of industrial farming system with very big fields with monocultures of crops that are treated with lots of pesticides. It's very difficult for most insects to survive in.
Why should we care about the insect die-off?
People should be jumping up and down and be concerned over this, because we cannot survive without insects. Pollination is probably the best-known example of what insects do for people. Sometimes it's bees, sometimes it's flies, beetles or whatever. Most of the fruits and vegetables we like to eat, and also things like coffee and chocolate, we wouldn't have without insects.
Insects also help to break down leaves, dead trees and dead bodies of animals. They help to recycle nutrients and make them available again. If it weren't for insects, cow pats and dead bodies would build up in the landscape.
Read more: UN report warns risk to bees and other pollinators threatens human food supplies
Sounds like a dystopia. What would a world without insects look like?
Pollination is necessary for most wild flowers. So if we lose most of our insects, then we're going to lose our wild flowers, which means that anything else that likes to eat wild plants will disappear. Insects are at the heart of every kind of ecological process you can think of. Without them, we would live in a sterile, dull world where we eke out a boring existence of eating bread and porridge.
What about pests like mosquitoes? Do they also have an ecological purpose?
All insects are doing something. They are either food for something, or they pollinate something or whatever. But not every organism has to have a purpose. It may be the case that one or two insect species go extinct and it wouldn't have any noticeable effect on anything. The concern is that if we lose more and more of them, ecosystems will slowly unravel.
Researchers found that insects in a nature reserve in Germany declined more than 75 percent. But that hasn't necessarily affected us and our crops, right?
The biggest crops grown in Europe don't depend upon insect pollination; wheat, for example, is wind-pollinated. Other parts of the world are starting to see the impacts of the loss of pollinators: In parts of China, they now hand-pollinate their apple and pear trees because they don't have enough bees left to do it.
So you are saying, we haven't experienced the full impact of the insect die-off?
That's right. We've got a growing human population trying to grow more and more food, and we've got a rapidly declining population of pollinators. Those two things are going to crash into each other. It can't be more than 10 years away, and probably less would be my guess.
Across the globe, butterflies are under threat. According to the German Wild Animal Foundation, the number of butterfly and moth species present in Germany has halved over the last 30 years. For diurnal butterflies, that decline is nearer 70 percent. This photo shows Colias hyale, which was selected as Germany's "butterfly of the year" in 2017.
Butterflies adore the sweet sap from flowers and blossoms, and enjoy a broad palate. But plant diversity is dwindling, particularly in regions where intensive monoculture agriculture dominates, which leaves little choice for our beloved butterflies.
Crop protection products like herbicides and pesticides destroy biodiversity. Wild herbs, plants or flowers can't survive in areas with monoculture farming. In many parts of Germany, the scarce Swallowtail butterfly pictured here was once a common sight, but has now vanished from the landscape.
The big problem is that pesticides aren't only harming butterflies. Studies show that some regions have seen 80 percent decline in insect numbers compared to 30 years before. Bees, bumblebees, dragonflies, wasps, flies, bugs and butterflies - they all struggle to survive in our intensive-agricultural world of pesticides and fertilizers.
A recent study shows that bird numbers are also in a decline. One reason: They can't find enough insects for food. The population of northern lapwings in Germany, for example, is estimated to have shrunk by 80 percent between 1990 and 2013. The number of whinchats has dwindled by 63 percent and black-tailed godwits by 61 Prozent.
Astonishingly, the butterfly decline is particularly obvious in the countryside. In towns and cities butterflies are more numerous. They thrive in parks, on cemeteries, on uncultivated land but even in city centers. Here, they obviously find the plant diversity which they miss in the countryside.
Read more: Supply chains at risk as pollinators die out
Why are particularly bee colonies in such bad shape?
Intensification of farming has resulted in a landscape with very few flowers, and when there are flowers, they're very likely contaminated with pesticides. That has made life pretty difficult for bees. Moreover, we've accidentally spread a whole bunch of bee diseases around the planet with moving domestic honeybees around. If you're a bee and you are sick and poisoned and hungry all at the same time, then it is not surprising you might die.
Will the ban on the open-air use of neonicotinoids in the European Union save the bees?
No. Some people wrongly believe that neonicotinoids are the main problem that bees face. Neonics do harm bees, and stopping using them is a wise and sensible thing to do. But we currently use about 500 different pesticides in Europe. Banning three of them, probably the worst three, is a good start — but there's still an awful long way to go. If you withdraw one pesticide, the farmer just wants to know which pesticide he can use instead. We really need to look at this whole system of farming and find a way to massively reduce pesticide use.
Which insects will suffer most from climate change?
Bumblebees are a classic example. They are big furry insects that are well adapted to cold climates, to cool wet temperate conditions, and they are really going to struggle as it gets warmer. There are predictions that many of our European bumblebees will disappear by the end of this century.
Read more: To save species, limit global warming
Will some species of insects also benefit from climate change?
Certainly some insects. The ones that can breed fast, that have big populations, that are adaptable. Those tend to be the ones that are pests, the ones that we don't want. Whereas butterflies, dragonflies and bumblebees breed much more slowly, they're less adaptable. So we do run the risk exterminating most of the beautiful and important insects that we love. And being left with lots of flies and cockroaches.
Dave Goulson is a professor of biology at the University of Sussex in the United Kingdom.
Sonya Angelica Diehn conducted the interview, which has been shortened and edited for clarity.
They are the pollination super stars! Honeybees account for about 80 percent of all pollination by insects. They visit a large variety of plants, collecting pollen and nectar taking it back to their hive. Each hive can collect about 66 pounds of pollen every year. As well as the honeybees, there are several thousand wild bee species. Most of those live a solitary life, not in hives.
They are bigger and hairier than honeybees, but just as useful: bumblebees also feed on floral nectar, using their long hairy tongues to collect the delicious liquid. Bumblebees are social animals like honeybees, but form much smaller colonies of only about 50 to 600 individuals.
Wasps have a bad reputation and the vast majority of wasp species play no role in pollination. That is because wasps have a smooth body without hairs, and pollen doesn't stick to them. Pollen wasps are different, though. They collect pollen and nectar inside their throats and feed their young with it.
These little creatures try to look dangerous by imitating the coloring of bees and wasps - but they are harmless and cannot sting. They are often seen hovering above flowers. The adults love nectar and pollen and are important pollinators. Hoverfly larvae are also useful: they feed on aphids and thus help with pest control.
They look a bit like a cross between a fly and a bee, hence their name. Bee flies can grow to up to four centimeters. They live in many parts of the world, but are most diverse in the tropics and subtropics. Adult bee flies love pollen and nectar; their larvae, though, feed on the eggs or larvae of other insects.
There are more than 18,000 species of butterflies, and most of them are brightly coloured. With their long, thin legs and relatively small bodies, they cannot carry as much pollen as bees. Still, they do a good job pollinating plants. Unlike bees, butterflies can see red which attracts them to different blooms than bees.
Moths are less colourful than butterflies, but they still belong to the same family. Moths fly at night. That's why they do not need bright colours. But they also feed on flowering plants. Some moths, and especially their caterpillars, are major agricultural pests, though.
Did you know that beetles also play a role in pollination? Some of them do, such as the flower scarab, also called flower beetle. As the name suggest, they visit flowers for pollen and nectar. There are around 4,000 species. One is the green rose chafer (photo).
It is not only insects that do the pollinator's job - there are birds on duty as well. Especially birds with long slim bills like hummingbirds carry pollen from one flower to the next when feeding on nectar. Some species of plants have even evolved to produce flowers that appear especially attractive to hummingbirds.
Some other birds belonging to the passerine group also appreciate floral nectar. Take this Seychelles sunbird. Its long, slender bill shows that it is specialized on drinking from flower blossoms. This species is especially fond of hibiscus flowers.
Bats - including their larger relatives, the fruit bats - play an important role in plant distribution and reproduction. While some bat species prefer insects, others feed on fruit or on nectar. When they drink nectar with their long tongues, they transfer pollen from one blossom to the next.
In Madagascar, primates like this mouse lemur pollinate flowers and are even essential to the reproduction of some tree species. They stick their noses into the flowers to drink nectar, and pollen collects on their snouts.
Yes, there are even some species of lizard and snake that help with pollination. Researchers found that, especially on islands, lizards are important pollinators. They suspect that lizards have fewer predators on islands and are therefore more numerous. On these islands they can roam around more freely and expand their diet to nectar, pollen and fruit.