Biologisk mångfald i små grönområden
Inventering av insekter och fåglar i bebyggda områden i Solna kommun
All over the world the urbanisation increases at the expense of green areas. Many plants and animals are endangered today because their habitats gets smaller or disappear. The green areas that are left in city centres and suburbs are often small and surrounded by roads and buildings. Despite this, several studies have shown that these small green areas may house large biological diversity.This project aims to study the biological diversity in small green patches in residential areas. The study has been carried out in Råsunda in Solna municipality (Stockholm county) during the period May?July 2006.Three equivalent areas (5000?10 000 m2) with quite many old oaks were chosen for the study and inventoried for birds and saproxylic insects. The results were compared with other studies in areas of different sizes, both inside and outside of suburbs. Birds were inventoried at eight occasions between 7.00 and 9.25 am. In each area a few places were chosen as inventory spots. These were distributed to cover the whole area. At each spot, all birds that were heard or seen during a ten-minutes-period were counted. Insects were collected by attaching a pitfall trap or a window trap to each of seven old oaks (Quercus robur).The results show that the patches, despite their size and nearness to buildings and roads, contained a high diversity of animal species. In total 26 bird species and ten orders of insects were found. The number of bird species in the present study are correlated with the number of bird species in residential areas and larger green areas in another study made in Örebro. There was however no correlation with inventories carried out in the city centre and the periphery in the same study. In comparison with the periphery, the areas in Solna had fewer species of woodpeckers, forest birds, hole-nesters and vulnerable species, but more urban species. Among the identified insects were three red-listed species, Lymexylon navale, Euryusa sinuata and Eupachygaster tarsalis, which all are attached to old deciduous trees. In addition, Eupachygaster tarsalis has previously only been found a few times in Sweden.A larger survey would probably have generated more species but this study have shown that even small green patches in residential areas can house a large biological diversity and therefore be important to conserve and take care of. To maintain this kind of diversity within residential areas, it is necessary to let trees grow old and protect green areas from further exploitation.