Bonn: Species decline

Data basis: Reinhardt; Harpke; Caspari; Dolek; Kuehn; Musche; Trusch; Wiemers; Settele, 2020 - Verbreitungsatlas der Tagfalter und Widderchen Deutschlands and own observations.

As almost everywhere in GermanyGermany, the habitats of plants and animals in Bonn, GermanyBonn have been reduced in size or destroyed in recent decades. Land areas have been homogenised or converted, sealed or built on. As a result, they have lost their ecological value.

As a result, Bonn, GermanyBonn has lost a large proportion of the butterfly species that used to occur there:

29 of the original 86 butterfly species in Bonn, GermanyBonn are extinct or considered lost (see Bonn: Species decline: Existing/extinct species). This is despite the fact that Bonn, GermanyBonn has a comparatively large and even protected forest area in the form of the Kottenforst, North Rhine-Westphalia, GermanyKottenforst. The forest species are doing well in Bonn, GermanyBonn, but the species adapted to other habitats are not doing at all; many of these species have disappeared.

The city area lacks open, inhomogeneous areas. There is a lack of unsealed, overgrown areas with interfering areas and spatial connections between them.

The main factors behind the dramatic loss of biomass and biodiversity (see Hallmann; Sorg; Jongejans; Siepel; Hofland; Schwan; Stenmans; Müller; Sumser; Hörren; Goulson; de Kroon, 2017 - More than 75 percent decline over 27 years in total flying insect biomass in protected areas), which is not only being observed in GermanyGermany, are:

• The loss of habitatsn
as well as
• The introduction of environmental toxins

Interestingly, human-induced climate change does not generally lead to a decline in biomass and biodiversity:

There are habitats in which species are disappearing due to the changed conditions caused by climate change, but these species can find suitable conditions again in other places. The prerequisite is, of course, that these places are also accessible to the species.

This means that a change of species can certainly take place in a habitat. It deliberately says can: Some species do not have the opportunity to relocate. This may also be due to the fact that the habitat they need simply no longer exists.

Butterfly species which are climate change winners in Bonn, GermanyBonn:

• Southern Small WhitePieris mannii (Mayer, 1851)Southern Small White
• Marbled FritillaryBrenthis daphne (Denis & Schiffermüller, 1775)Marbled Fritillary

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As a child, I often went on Sunday outings with my father and brothers to the nearby Wahnbach dam (the Bonn drinking water comes from there).

We always took a short walk over the dam wall through a small wooded area back to the parked car. When we stepped out of the forest, we were greeted by a beautiful, cool and damp wild meadow bordered by hedges and trees.

It was always a great pleasure to be able to observe the very special insects and butterflies there!

We travelled to the Wahnbach dam again on a spring Sunday and the anticipation was huge. We walked over the dam wall and then turned off into the forest.

When we emerged from the forest, I thought at first that we had taken the wrong path: The colourful meadow had disappeared! Many of the hedges and trees had been removed. Instead, there was just uniform short green grass. It wasn't even a private garden. It looked more like an unused area belonging to the water supplier. Insects and butterflies were now to be found in vain.

The micro-climate there was also completely different now. Presumably, the area had been drained and restored to an orderly state with German thoroughness. But why?

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A good 30 years later, I finally made a trip to the Wahnbach dam with my children. I couldn't find the place described again. Apparently the route is now different and/or the spot is now wooded.

In the Greek Rhodopes, however, I had déjà vu in 2019:

There I found the lost wild meadow again!

The loss of butterfly species in Bonn, GermanyBonn could be halted and partially reversed.

This would not require the creation of further nature reserves and the erection of fences. Quite the opposite! Only sensitive areas or areas with high visitor pressure need special protection.

Countermeasures in forest areas

Most butterfly species in GermanyGermany do not live in forests, but in open areas Settele, 1999 - Die Tagfalter Deutschlands. Heterogeneous areas are ideal for high species diversity and permanent populations.

To create or restore such areas, part of the Bonn, GermanyBonn forest paths should be provided with a low, overgrown fringe several metres wide in suitable places. The fringe should be kept as free of bushes and trees as possible through regular maintenance measures.

Not every woody plant that grows there should be removed: pioneer plants that colonise the area bordering the forest should be left standing. These include, for example, Goat WillowSalix capreaPussy WillowGoat Willow and Common AspenPopulus tremulaTrembling AspenCommon Aspen, which are very valuable for insects. Until now, these woody plants have often been removed, particularly due to their low economic value.

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In some places in the Kottenforst, North Rhine-Westphalia, GermanyKottenforst there are already such fringes. On the path running parallel to the A565, the approx. 10 metre wide fringe is occasionally used for the storage of felled logs, which was probably also the reason for these fringes. Although this puts a strain on the fauna, these areas are characterised by a comparatively high species diversity for the Kottenforst, North Rhine-Westphalia, GermanyKottenforst.

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If suitable (e.g. soil conditions, light exposure, microclimate, neighbouring areas), a few existing forest areas should be cleared on a large scale. Once the humus layer has been removed, they would once again provide a habitat for many species that have disappeared. Examples of these species include the orchid species that used to be abundant on the Venusberg. The Marsh FritillaryEuphydryas aurinia (Rottemburg, 1758)Eurodryas auriniaMarsh Fritillary would also be a possible candidate for reintroduction.

Some of the open areas created by the bark cutter in recent years should be kept permanently low.

Overall, the forest would lose a few per cent of its total area. However, species diversity and the number of individuals of plants and animals would increase disproportionately.

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Regular, targeted tree felling should be maintained: On the one hand, they generate revenue, which can also be used for forest maintenance and the above-mentioned measures. On the other hand, they create space for the existing trees to develop better.

Less hunting and thus a higher game population should naturally increase the number of open areas.

Countermeasures on agricultural areas

Flower strips and the planting of hedges along borders or separations could once again create important habitats for mammals, birds and insects.

Existing agricultural land could be completely converted into ecologically valuable areas.

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Fortunately, the above-mentioned flower strips have already been established on the Meßdorfer Feld, North Rhine-Westphalia, GermanyMeßdorfer Feld!

In Bonn, GermanyBonn, a lot has changed for the better in recent years with regard to the creation of valuable natural areas!

Countermeasures on other areas

Existing areas with ecologically less valuable vegetation (e.g. lawns) should be converted into valuable biotopes. This could not be achieved by simply not maintaining the area. Rather, depending on the respective conditions, suitable biotope types would have to be specifically identified by specialists and realised through appropriate measures. Regular maintenance measures, e.g. through mechanical activities or grazing, should preserve the biotopes in the long term.

The Bonner General Anzeiger wrote in an editorial commentary on 31 August 2022 on the subject of the destruction of natural areas:

Of course, the growing city needs green spaces and fresh air corridors. But it also needs space for economic development. Trade and industry in particular create jobs that are important for the social balance in society.

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Although the commentary does not take a clear position: The killer argument jobs all too often justifies the irretrievable destruction of natural space. Who is supposed to preserve natural areas at all? The other cities/municipalities? However, they could argue in the same way and thus legitimise the destruction of their land - which they probably do. Everyone seems to be closest to themselves.

It becomes very unpleasant when nature conservation is counteracted with cynicism. One example is the European HamsterCricetus cricetus (Linnaeus, 1758)European Hamster: ... and then the conservationists find another field hamster that prevents the construction of our project, which is extremely important for the region, and thus jeopardises important jobs!.

What will be the consequences for us and future generations if we continue to destroy nature for economic reasons? Are economic reasons often just a pretence and are we really only interested in satisfying our personal vanity and our own status (as high as possible) in our society?

Everyone actually wants nature conservation. But when it comes to changes in our own behaviour or even the loss of status symbols, the acceptance of measures is quickly over.

I have the feeling that many in our society believe that they have earned or honestly deserved nature-destroying privileges with their hard work: unrestrained and uninhibited consumption. Cars with arbitrarily high electricity or fuel consumption. Driving at unnecessarily high speeds. Frequent and long journeys. Maintaining personal behaviour of any kind.

In my home city of Bonn, GermanyBonn, nature and climate protection measures, even if it is only the promotion of inner-city cycling, are currently being vehemently opposed by business associations such as the Chamber of Industry and Commerce or the Bonn Rhein-Sieg Euskirchen Retail Association. In my opinion, this is about protecting the vested rights of the association members or the associations themselves. Nature conservation? Of course, but for us everything should stay as it is!.

I have a suggestion for a 100-year project:

One half of all habitats on earth is allocated to humans, the other half to all other living beings.

And in such a way that each of the halves is as self-contained as possible and must not be damaged or affected by the other half.

Obstacles

In addition to financial resources and political will, the above-mentioned measures require above all broad public acceptance.

Communication and information are important elements here.

We only protect what we love.

We only love what we know.

We only keep what we would miss.