Establishing development limits to protect valuable biotopes
In addition to a small-scale structure and varied landscape, time is an essential element for species diversity in a city. Parts of old city parks and unused areas are managed less intensively, so specific biotopes may evolve here over time. In Hamburg, for instance, two-thirds of all special plants occur in only one or two places. [Der Naturschutzrat, 2008]
Therefore it is important to protect such locales, because these special biotopes may be destroyed forever by a construction activity in the neighbourhood. It is possible to create conditions for the development of specific biotopes, but it is not possible to create a biotope.