Carabid beetle assemblages along urban to rural gradients: A review

Urbanisation causes similar landscape patterns across the world; cities are characterised by a densely populated and highly disturbed urban core, a less disturbed suburban zone and a least disturbed rural surroundings. In 1998, we set up a project to investigate the effects of this urbanisation gradient on the responses of carabid beetles (Carabidae, Coleoptera) in different cities across the globe. To date, eight cities have participated in this project and the findings can be summarised as follows. In general, carabid abundance and species richness increased from the city centres to the rural surroundings. Forest specialist species tended to be more common in suburban and rural zones, while open-habitat species predominate in the urban core. The highly disturbed urban environments were also generally characterised by a few dominant species and species capable of flight, while suburban and rural areas were characterised by larger-sized species and species incapable of flight. Deviations from these general patters do occur, notably the occurrence and high abundance of introduced carabid species in urban Edmonton, Canada. The challenge now is to infer process from these patterns. In particular, community and species specific responses need to be related to characteristics of the urbanised landscape, i.e. the urban–rural gradient needs to be operationalised in terms of specific disturbance features. Furthermore, the results should now be communicated to decision-makers so that they can be considered in planning.