Prof. Dr. Josef H. Reichhof
HENN Akademie, June 14, 2007
In the beginning was nature. Then the towns and cities emerged and spread out and consumed it all. They replaced the natural world with the artificial one of the total world of human beings. Trees and flowers are planted there according to human perceptions and other forms of life are tolerated if need be. This is how we come to the current cliché about the contrast between towns and nature. But this is wrong.
The developments refuted the ideas of the lack of nature. In fact, on average considerably more species of animals and plants live in the towns and cities than in equally sized areas in the “open countryside”. Even nature reserves often contain a smaller wealth of species than the large towns and cities. In a large city area of Berlin of 880 km², we find representatives of two thirds of all breeding bird species of Central Europe. Even in the more densely built-up area of Munich, we find 110 species representing half of all Bavarian species of breeding birds. These include a lot of rare species.
The diversity of the species increases markedly with the size of the cities. The frequency of birds in the cities largely exceeds that in the surrounding countryside. On average there is at least one pair of breeding birds per inhabitant. Cities accommodating several million inhabitants also accommodate millions of birds. Highly diverse is the spectrum of butterflies and wild growing plants. The city area of Nuremburg has twice as many plant species compared with the same size areas surrounding the city.
The reason for the great richness of species in urban areas becomes most evident amongst the butterflies, which are sensitive to environmental factors. Their diversity actually declines where the over-fertilized, intensively farmed surrounding land starts. Because of developments in agriculture, the cities have become islands and archipelagos of great species diversity in the cultivated landscape. Their potential for animals and plants in the wild should no longer be underestimated, because after all, city landscapes occupy more than five times the area of nature reserves in Germany.
For some species, the cities now represent actual refuges, such as in Berlin, where there are more than 1000 breeding pairs of nightingales. Peregrine falcons, which were threatened with extinction just a few decades ago, now breed successfully on towers and high buildings. There are four principal reasons for the species diversity in towns and cities: they have plenty of structures, the soil and gardens are hardly, if at all, fertilized and animals in the wild, which are otherwise shy, are almost no longer persecuted. In addition, the warmth of the cities encourages the diversity of species. All this should be taken into account even more in urban development than has hitherto been the case. The much demanded building infill should accordingly be considered critically. It threatens to destroy the centres of species diversity.
Prof. Dr. Josef H. Reichholf has worked as a scientist at the zoological state collection in Munich since 1974, as head of the main vertebrates department. Extensive teaching at both Munich universities, including, during the 1980s, lectures on municipal ecology as part of the post-graduate course in town planning at the Architecture faculty of Munich Technical University. Prof. Reichholf is a member of the Commission for Ecology of the Bavarian Academy of Sciences and is a holder of the "Treviranus Medal", the highest award for German biologists. The main areas of his research are ecology and evolution biology.