22.5.2014: Forschung international

Globale Analyse der Artenvielfalt in Städten

Analyse globale de la biodiversité des villes


Myla Aronson et al.

Eine Studie in 110 Städten aus allen Erdteilen ergab, dass die Vielfalt von Pflanzen und Vögeln in der Stadt im Vergleich zu den angrenzenden ländlichen Gebieten deutlich tiefer liegt. Für bestimmte Arten sind Städte allerdings wichtige Lebensräume. Eine intelligente Stadtplanung nach dem Konzept der grünen Infrastruktur wirkt sich günstig auf die Qualität der Stadtlebensräume und auf gewisse Arten aus und kann dazu beitragen, Biodiversitätsverluste im Zusammenhang mit der Ausdehnung der Städte zu mildern.

L'étude de 110 villes dans toutes les parties du monde a montré que la diversité des plantes et oiseaux est nettement plus basse comparé aux régions campagnardes adjacentes. Toutefois, les villes peuvent offrir d'importants habitats pour certaines espèces. Une planification urbaine intelligente ayant recours au concept d’infrastructure verte a une répercussion favorable sur la qualité des milieux naturels et sur certaines espèces et peut ainsi contribuer à diminuer la perte en biodiversité dû à l'étalement urbain.


Cities currently cover around 3% of the Earth’s surface and harbour around 70% of its human population. Urban populations are expanding faster than the rate of global population growth as, increasingly, people are moving from rural to urban areas. Urban sprawl can have severe effects on local wildlife by degrading habitats and disrupting migration routes.
Cities share structural characteristics, creating similar habitats across the globe. Combined with a higher risk of introduction of non-native species than in rural areas, it is thought some urban species have become ubiquitous, so-called 'cosmopolitan species'. Invasions of cosmopolitan species and reductions in local biodiversity are thought to lead to global similarity of urban biodiversity.
Previous research has focused on the effects of urbanisation over individual regions or for particular cities. However, the present study investigates how urbanisation affects biodiversity on a global scale, and identifies human activities that drive biodiversity loss.
The researchers analysed data on plants in 110 cities and data on birds in 54 cities around the world to determine the diversity of native and non-native plant and bird species in each city. They also analysed the data for patterns and predictors (both human and natural) of urban species diversity, such as the percentage of natural vegetation or urban land cover within a 15 km radius of the city centre, city age, annual average temperature and latitude. The results for each city were also compared to estimates of biodiversity in nearby undeveloped areas.
Cities contained, on average, only 8% of the native bird and 25% of the native plant species found in nearby undeveloped areas. Despite this, a total of 36 bird and 65 plant species of conservation concern were supported in cities. Threatened plants were found in 8% of cities and 30% of cities were home to threatened bird species. Four «cosmopolitan» bird species were found in more than 80% of cities, such as the rock pigeon (Columba livia) in 51 cities, and 11 «cosmopolitan» plants were found in more than 90% of cities, such as the annual meadow grass (Poa annua) in 105 cities.
For both plants and birds, species diversity in cities was best explained by anthropogenic features of the city, such as city age, rather than natural factors, such as average temperature. The diversity of bird species was most negatively affected by urban land cover, indicating that vegetation is an important factor for bird conservation. Plant species were positively affected by city age and, unsurprisingly, higher percentages of intact vegetation were found to preserve plant species.
Taken together, the findings indicate that although urbanisation has significant, negative effects on biodiversity, cities are able to provide a refuge for some threatened species. Improved urban planning and conservation efforts within cities, such as preserving and restoring native vegetation and establishing sufficient green spaces, could reduce the biodiversity declines associated with urban expansion, the researchers conclude.

Quelle: Science for Environment Policy


Keywords:
Stadt, Siedlungsraum, grüne Infrastruktur, Artenvielfalt



Literatur:
Aronson M. et al. (2014): A global analysis of the impacts of urbanization on bird and plant diversity reveals key anthropogenic drivers. Proceedings of the Royal Society B: Biological Sciences 281 (1780). DOI:10.1098/rspb.2013.3330.
http://ec.europa.eu/environment/integration/research/newsalert/pdf/370na2.pdf

Kontaktadresse:
Myla F.J. Aronson, PhD.
Department of Biology
Hofstra University
Gittleson Hall
Hempstead, NY 11549
Myla.aronson@rutgers.edu


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