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Insects and their role in the ecosystem

Insect news rarely reaches a large audience. But in 2017 the "Krefeld study" went around the world: A team of researchers had found that more than 75 percent of the total mass of flying insects had disappeared from parts of Germany. To do this, they used data from the Krefeld Entomologists' Association. The Insect Science Association, to which individual researchers from the team belong, evaluated the populations at over 60 locations in Germany using standard flight traps between 1989 and 2016. The researchers found that not only is the number of insects falling dramatically, but also that biodiversity is massively endangered. Since then, the topic has been on everyone's lips, and more and more studies are known.

Even if some six-legged friends are annoying when they prance around on the bread and jam at breakfast or their humming robs us of sleep: bees, butterflies, beetles and the like are indispensable for the ecosystem. Experts warn that insect decline is putting entire food chains at risk. Because insects serve as food for many species such as birds, frogs and bats. In addition, a large part of the crops is dependent on pollinating insects. Without them, there would be major crop failures, especially for fruit and vegetables.

The causes of insect decline are diverse and not yet fully understood. Experts assume that the intensification of agriculture plays a major role. The dwindling diversity in the fields and the use of pesticides in industrial agriculture endanger the insects. In addition, industrial and residential estates are reducing their living spaces. Light pollution is also related to increasing population. Many insects are nocturnal, and the lighting in the cities disrupts their day-night rhythm as well as their hunting and reproductive behavior.

The "death of insects" and the protection of animals are closely followed and discussed in the general public. And there is civic engagement: schools set up insect nesting aids and many plant enthusiasts begin to garden close to nature. Politicians are also active: in 2019 the federal government passed the "Insect Protection Action Program". At the beginning of 2021, it will bring an insect protection law in motion. Together with the federal states, it has developed a systematic nationwide insect monitoring system. And in March 2021 it set up a national center for biodiversity monitoring in Leipzig in order to improve the monitoring of species and habitats beyond insects. Because it's not just about small animals, but about the big picture.

Small animals - big impact

Insects are the most species-rich group of all living things and make up a good 70 percent of all animal species worldwide. This ratio also applies to Germany: around 48,000 animal species have been recorded here, including over 33,000 insect species. They are an essential part of biological diversity and can be found in almost every habitat.

Insects fulfill important ecological functions. On the one hand, they are the basic food for many animals such as birds, mice, frogs and lizards. Their lives are in danger if they can no longer find enough to eat. On the other hand, insects play an important role in ensuring that the soil remains fertile and the water remains clean. Without them, the material cycles in nature would collapse. One example of this are insects living in the ground: these help to compost leaves and wood and break down other animals' dung.

In addition, insects are invaluable for human nutrition. Their pollination performance is particularly important for fruit and vegetable cultivation, but also for large-scale arable crops such as rapeseed, sunflowers or broad beans. According to the World Biodiversity Council, three quarters of the world's most important crops are dependent on pollination, albeit to different degrees. Researchers at the University of Hohenheim calculated the economic benefits of pollinators in 2020: If all pollinating insects were to disappear, Germany would lose an average of around 3.8 billion euros. Per year.

The pollinators include wild and honey bees. In addition to them, just as many butterflies, flies, beetles or wasps pollinate plants. In addition to these insects, some birds are also among the pollinators, but insects play the crucial role. In the forest ecosystem, around 80 percent of all trees and bushes are pollinated by insects. These include maple, hawthorn, horse chestnut, willow, rowan and linden. Ants also contribute to the spread of the plants: They collect seeds and distribute them.

The many are getting fewer

In Germany, in addition to the "Krefeld Study", there are also special studies on the populations of butterflies, wild bees and cicadas. All surveys show that the number of species, but also the size of the populations, are falling dramatically in some cases. The "European Grassland Butterfly Indicator" - a kind of EU butterfly indicator - reports on the development of ten specialized and seven common butterfly species. According to the indicator, their number decreased by a third between 1990 and 2015 - and not only in Germany, but also in other European countries.

More than half of the 561 wild bee species in Germany are already on the red list and their population is threatened. Over a period of 46 years, the number of nests of a narrow bee species fell by 95 percent in the Swabian Alb. In the Isar floodplains in the Bavarian town of Dingolfing, three quarters of the wild bee species have disappeared in just a decade.

In addition to long-term and individual studies, the so-called Red Lists in particular provide information on the endangerment of individual species. The Federal Agency for Nature Conservation has been publishing this extensive collection for over 40 years. The lists show that almost every second insect species recorded is declining nationwide: 42 percent of the recorded species are endangered, extremely rare or already extinct. The declining population trend was 96 percent for caddis flies and 60 percent for ants.

Why are insects threatened?

The causes of insect death are many and varied. Experts blame several factors for this: the loss of living space through settlements and traffic areas, light pollution in and around settlements, but above all intensive agriculture. An international team of researchers found that the insect biomass on grassland areas such as fields and meadows decreased by two thirds between 2008 and 2017.

Insects can no longer find food in ever larger fields. With the disappearance of hedges, fields and flowering slopes, habitats are being lost. Monocultures reduce the food supply; the use of fertilizer increases the nitrate content in water and soil, which harms all insects that are adapted to a nutrient-poor environment. Many pesticides not only decimate pests, but also many other insects and their habitats. Broad spectrum herbicides such as glyphosate destroy so-called accompanying flora such as cornflower, poppy and chamomile and thus the basis of life for many insects.

The use of neonicotinoids has been and is much discussed. These active ingredients were approved for use in agriculture in the 1990s to control pests. But they also play a part in the death of insects. In 2018, the European Union banned the use of the three insecticides imidacloprid, clothianidin and thiamethoxam outdoors. They belong to the neonicotinoid group of active ingredients.

In intensive agriculture, the variety of flowering plants is also lost through too frequent mowing. The nature conservation organization NABU points out that the landscape in Germany will be "poor in flowers" from June when meadows and pastures are mowed.
The loss of orchards, which are used as habitats by many insects, is also problematic.

What can you do to protect yourself?

There are already many approaches to protecting insects. The municipalities and citizens create flowering meadows, plant flowering traditional trees or install nesting aids for wild bees and the like in the urban area.

Politicians are also reacting decisively. The central measures of the action program insect protection include:

  • Legal protection of insect habitats (e.g. through orchards and species-rich grassland).
  • The use of glyphosate-containing pesticides is to be significantly restricted from 2020. The use of glyphosate is expected to end entirely at the end of 2023.
  • Every year there is an additional 100 million euros for the promotion of insect protection, especially in the agricultural landscape, and for the expansion of insect research.
  • Insect habitats such as the verges of paths or hedges along the way should be protected and restored.
  • Significantly fewer pesticides and other pollutants should be introduced into insect habitats.
  • Lighting that is harmful to insects should be restricted.

Important legal changes envisaged in the action program are to be summarized in an insect protection law. To this end, in February 2021, the Federal Cabinet launched a third law amending the Federal Nature Conservation Act, which was essential for the program of action.

What can I do about insect death?

Each individual can also make a contribution to creating more habitats and a better food supply for insects. When shopping and gardening in the garden or on the balcony, there are numerous ways to protect insects:

  1. Buy organic food: These are not treated with synthetically produced pesticides and mineral fertilizers in the field.
  2. Gardening close to nature: In your own garden or on the balcony you should avoid artificial pesticides and fertilizers. There are natural alternatives such as horsetail brew or nettle manure.
  3. Set up insect hotels: Because it is becoming increasingly difficult for insects to find natural shelter and nesting opportunities, "insect hotels" in the garden and on the balcony are a good idea.
  4. Laying clay sand areas: Many wild bees, such as mason bees or bumblebees, nest in the ground. They like to dig their tunnels in rain-protected areas from a mixture of sand and clay.
  5. Colorful mix: insects need a variety of pollen and nectar. That is why wildflower meadows should be sown. Local perennials, shrubs, hedges and fruit trees also provide a lot of food.
  6. Stand or leave dead wood in the garden: Rotting wood is the ideal habitat for insects. Birds will also find enough food there for their offspring.
  7. Insect-friendly lighting: UV, blue and white LED light attracts most insects. The more red there is in the light, the fewer insects are attracted. When buying lamps for outdoor use, care should therefore be taken to ensure that the light contains as little blue as possible.

Related Links

The Insect Atlas 2020

Action program insect protection

Less bees, flies, butterflies
https://www.nabu.de/tiere-und- Pflanzen/insekten-und-spinnen/insektensterben/index.html

Insect decline: data, facts and need for action

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