Cities differ from rural landscapes in many ways: Human densities peak in urbanized areas; pollutants, energy and nutrients concentrate there (Sukopp 1998); exotic species are more frequent and land use is more heterogeneous (Niemelä 1999; McKinney 2002; Kühn
2004a); annual average air temperature is 0.5 to 1.5°C higher than in the non-urban surroundings and air moisture is reduced, at least in temperate and boreal zones (Sukopp 1998). In contrast to cities, many agricultural landscapes are homogeneous over large areas. They are often subjected to a highly industrialized agriculture, characterized by high pesticide and fertilizer input and water management aiming at the maintenance of favorable soil moisture conditions. Forested and semi-natural landscapes are often nutrient poor, like forests on siliceous rock or heathland, because many nutrient rich habitats were transformed to agricultural or urban habitats (cf. Pressey 1994).