How many different kinds of leaves can you find in the picture? Have you any idea what they might be? Which insects eat them? Which animals depend on the insects? And this picture is from a relatively poor garden in terms of biodiversity!
One of the biggest challenges for our planet at the moment is the loss of biodiversity worldwide. The following link is a comprehensive report from the UN in 2019 showing the loss of biodiversity on or planet, but also what we can do about it, if we were to get our act together! https://www.un.org/sustainabledevelopment/blog/2019/05/nature-decline-unprecedented-report/
So what can we do ourselves? One possibility is to ask garden owners to tolerate a bit of disorder. The picture below shows a few helpful tips e.g. leave a dead tree standing, let hops grow over wire fencing, leave bundles of twigs stacked as possible refuges, encourage native plants such as hazel or blackberries to grow.
Politics: International and Regional
Another possibility is to politically support organisations which wish to alter subsidies to farmers, so that they receive benefits for leaving parts of their land fallow, which works as a refuge for a wide variety of plants and animals. As the EU is instrumental in determining the environmental policy of the member states, it is useful to get in touch with the local MEP. https://europa.eu/european-union/topics/environment_en
On a local level, write to the local Bezirk, asking them to not mow grass verges too often, leave dead wood lying and plant indigenous species in the parks.
Example Grünflächenamt Steglitz-Zehlendorf. https://www.berlin.de/ba-steglitz-zehlendorf/politik-und-verwaltung/aemter/strassen-und-gruenflaechenamt/gruenflaechen/