Munich study confirms severe decline in insect populations in Germany

In October 2017, a long-term study by the Entomological Society Krefeld hit like a bomb: Within thirty years, the number of flying insects in Germany was said to have decreased by three quarters.

Now a research team led by Sebastian Seibold and Wolfgang Weisser, who teach terrestrial ecology at the Technical University of Munich, is confirming the reported decline. The biologists published their results on 30 October in the journal Nature.

“Previous studies have concentrated either exclusively on biomass, i.e. the total weight of all insects, or on individual species or groups of species,” said Seibold, head of the research group, highlighting the special nature of his new research work. His group combined both approaches. 

Read more: To stop an insect die-out, the world needs pollinator-friendly policies, scientist warns

• What have insects ever done for us?

  Planet of the insects

  From pretty butterflies to pesky mosquitoes — insects are among the most diverse and dominant groups on earth. Nearly 1 million species are known to exist and there are likely many more to be discovered. According to a UN biodiversity study, up to 40% of insects species are threatened with extinction in some parts of the world. Many people do not realize that their loss would be keenly felt.

• What have insects ever done for us?

  Skilled pollinators

  Crops, such as wheat, are wind pollinated, but many other food crops depend on insects for pollination. Their disappearance would come at great cost to farmers. Some $235 billion of yearly global food production relies on pollinators. In some farms in China, workers are hand-pollinating apple and pear trees because of the lack of bees. Such labor-intensive work pushes up food prices.

• What have insects ever done for us?

  Poorer plates

  Pollinator disappearance also means we’d lack much of the fruit and vegetables we eat — and we wouldn’t be enjoying beloved treats like chocolate and coffee. Apart from food, pollinators also contribute to the fibers, such as cotton, from which we make our clothes, as well as to plants on which certain medicines are based.

• What have insects ever done for us?

  Nature’s cleanup crew

  Many insects, like the dung beetle pictured here, decompose dead plant matter, carrion and feces that would otherwise be left to decay in our environment. Basically, the world would be a smellier and less hygienic place without them.

• What have insects ever done for us?

  A meal for other creatures

  Insects are the main source of food for many other animals, including amphibians, reptiles, certain mammals, and birds. And as insects disappear, there could be declines in the species that feed on them too. Ornithologists believe sharp declines in bird species in the UK, for instance, are at least partly linked to a drop in insect numbers.

• What have insects ever done for us?

  Difficulties adapting

  Climate change is also affecting insects that are slow to adapt. Bumblebees for instance are suited to cool and wet climates and may find it difficult in warmer weather. But insects that are pests are already spreading to new habitats. The European corn borer (pictured), which can destroy corn harvests, is among them. That means farmers use more pesticides that kill pollinating insects.

• What have insects ever done for us?

  No place for pollinators

  Intensive farming is one of the major factors behind insect declines in Europe. Fertilizers, pesticides and insecticides are all driving the decline, as are monocultures — the practise of growing of a single crop or plant. That takes refuge and habitat, like diverse flowering meadows, away from insects.

• What have insects ever done for us?

  A home for insects

  Experts say a more insect-friendly farming policy that relies less on pesticides and monocultures would boost their numbers. But planting blooming flowers in gardens and urban areas would also provide food and habitat for bumblebees and butterflies. Another option is building more “insect hotels,” (pictured) for solitary critters, like leafcutter bees, which like to nest in tunnels.

  Author: Jennifer Collins

Forests and meadows

Between 2008 and 2017, the scientists regularly counted flying insects as well as other arthropods such as spiders and millipedes in three regions of the country. The study looked at 290 sites with forests and grasslands on the Swabian Alb in southern Germany, in Hainich – a wooded ridge in Thuringia – and in Schorfheide in the northern state of Brandenburg.

The scientists examined 150 sites in grasslands twice a year. They collected the animals from the grassland with nets. Of the 140 forest sites, 30 were examined each year, the remaining locations were investigated three times within a decade. The biologists caught the insects there with traps.

In total, the scientists analysed data from more than one million insects and other arthropods belonging to more than 2700 species. They also took fluctuations in the weather into account in order to exclude measurement errors as far as possible. 

Read more: ‘We cannot survive without insects’

Decline by up to two thirds in ten years

Both on meadows and in forests, the number of species decreased by about one third during the study period. Their total mass also decreased, especially in grasslands, by 67 percent. In the forests it shrank by about 40 percent. According to the researchers, the decline is presumably related to agriculture. “We did not expect such a decline to be observed over only a decade,” Weisser said. “This is frightening, but it fits into the picture that more and more studies are drawing.

In a commentary on the study biology professor William Kunin of the University of Leeds came to the conclusion that the verdict is clear and at least in Germany the insect shrinkage is real and as bad as previous studies sugggested. The study provides the strongest evidence of insect mortality available to date, he pointed out.

It has something to do with agriculture

The researchers were able to establish a connection with land use at the individual sites. This ranged from meadows where sheep grazed only a few days a year and which otherwise remained largely untouched, to heavily farmed areas which were fertilised and mown several times a year. Cattle grazed on some areas for about a third of the year.

They also divided the forests into three categories, from little to heavily farmed. Insect shrinkage was particularly pronounced on grasslands surrounded by arable land. There, the biomass of species that did not cover long distances shrank in particular. Possibly these insects would have worse chances if their habitat was surrounded by a lot of arable land.

In the forests, it was mainly species that were disappearing that travelled long distances. “We still have to find out whether more mobile species from the forest come into stronger contact with agriculture during their migration or whether the causes are also related to the living conditions in the forests,” said Martin Gossner, another TUM researcher involved. 

Read more: How to stop an insect apocalypse

What to do?

Federal Environment Minister Svenja Schulze (SPD) expressed her alarm to the German Press Agency: The study once again demonstrates how serious the situation is, she acknowledged. “The way in which insects are used in agriculture plays a decisive role in determining whether they can survive in their environment,” she said.

Author Seibold emphasised that it was not enough just to maintain individual areas and retreats to combat insect decline. “To stop the decline, we need […] greater coordination and coordination at regional and national levels,” he said.

“The study shows us that agriculture must be part of the solution,” Joachim Rukwied, President of the Farmers’ Association, argued. “Hardly any other sector is as dependent on the pollination performance of bees and insects as we are.” He added that the Farmers’ Association was backing “cooperative nature conservation.” As an example he gave an initiative to give some arable areas back to nature: “This year we [voluntarily] created flower strips nationwide as a habitat for insects with a length of over 230,000 kilometres – a five-metre-wide strip that extends almost six times around the world.”

Nature conservationists, however, are calling above all for a ban on insecticides – such as neonicotinoids, which France has already banned, or the herbicide glyphosate. Glyphosate has been criticized for harming biodiversity. Meanwhile, experts are debating whether such bans are really effective. There is also a danger that, after a ban, farmers will resort to other pesticides that are no less dangerous. 

• Bees — what are we without them?

  Sugarsweet crystals

  What can be seen here is probably the first thing that comes to mind when we think of bees — honey! Here the sugar crystals have been magnified 100 times with the help of a polarized light. For one jar of honey, bees have to visit between 450,000 and 3 million flowers.

• Bees — what are we without them?

  Visibly empty

  Many people don’t realise that honey is just a fraction of the food bees help produce. The above photo shows what a supermarket would look like if bees didn’t exist. That amounted to 60% of the items on the shelves. Various spices, marinades, dairy products, and even scented toilet paper, are all possible in part thanks to the efforts of bees.

• Bees — what are we without them?

  #Notallbees

  Not all bees are the same. A wild bee, for example, does not produce honey but it’s a key pollinator. It’s also particularly at risk of extinction. Bumble bees are also among the wild bee species. Honey bees, on the other hand, have less to worry about because they are domesticated and highly managed for agricultural use, with their hives kept by humans.

• Bees — what are we without them?

  An apple a day no more

  Of course there are other pollinators besides bees — butterflies, flies and birds, for example. But about a third of our fruit and vegetables rely on pollination by bees. These include apples, pears, strawberries and cucumbers. And we would all be reluctant to do without them, wouldn’t we?

• Bees — what are we without them?

  Beeswax is vital to our food industry

  How is it possible for our chocolate, sweets, fruit and vegetables to look so beautiful? Bees, of course. Or, more specifically, E901 — beeswax. It gives chocolate its beautiful shine and makes vegetables look waxed and appetizing, as well as ensuring they retain moisture and stay fresh. It’s also used as a glazing and separating agent for candy so that gummy bears don’t all stick together.

• Bees — what are we without them?

  No more cocoa, either

  And about chocolate — without bees, there wouldn’t be much of it. Bees are responsible for pollinating a lot of cocoa. If it came to it, the only option could be to pollinate by hand, which would be extremely labor-intensive and much less efficient. The same goes for nuts, by the way.

• Bees — what are we without them?

  Coffee kicks for everyone

  It’s not just humans that like coffee. Bees do too, as an experiment with coffee-free and coffee-infused sugar water has shown. At the same time, bees do the work to pollinate our coffee beans, to maintain our (hopefully) never ending supply of caffeine.

• Bees — what are we without them?

  A toast to our bees!

  By now it’s clear how much we benefit from the hard work of bees and how different our lives would be without them. But we shouldn’t just pay tribute to them on World Bee Day. Appreciating bees means protecting them. The most restrained use of pesticides helps. Insect boxes also provide safety, nesting and hiberation. And flowers in a balcony box or fruit trees outside are a safe source of food.

  Author: Hannah Fuchs, Charli Shield

Read more: Beetle mania: The planet’s most successful creatures?

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Article source: https://www.dw.com/en/munich-study-confirms-severe-decline-in-insect-populations-in-germany/a-51052955?maca=en-rss-en-all-1573-rdf