Are urban green spaces suitable for woodland carabids? First insights from a short-term experiment

One consequence of the spatial expansion of cities is the multiplication of highly fragmented and diverse green spaces immediately surrounded by urban areas. Whereas the global expansion of urban areas is a growing concern for the viability of woodland arthropods, the suitability of green spaces as refuges to arthropods needs to be clarified. In order to assess and compare the survival rates of the woodland carabid Abax parallelepipedus in four types of green urban sites (remnant forest patch, urban park, woody corridor and set of gardens), we conducted a Capture-Mark-Recapture experiment based on 483 individuals collected in a forest located in a natural landscape (considered as the control site) and released into the various green spaces. Results indicated strong heterogeneity in survival probability between green spaces. Survival rates were slightly higher in the control site than in the remnant forest patch, the urban park and the corridor, which appear suitable for the survival of the species. However, it was substantially lower in the gardens. The analysis further revealed that these differences in survival are largely explained by the differences of within -site habitat fragmentation. By indicating that urban green spaces may contribute unequally to woodland carabids survival, our study highlights that the modification of local environmental conditions alone (increase of temperature, increase of soil pollution and change in food availability) could not explain the negative effect of urbanization. This study argues for the development of corridors in cities in order to favour the colonisation of green spaces by woodland carabids.