Urbanization puts enormous pressure on the earth’s ecosystems; it directly and indirectly impacts biodiversity and ecosystems by modifying hydrology, biogeochemical cycles, energy flow and nutrient cycles. However, the conversion to and expansion of urban areas is a very complex process, involving different aspects working at different spatial scales. To better understand how urbanization affects ecosystems, it is therefore essential to include the spatial aspects of urbanization. Within Western Europe, Flanders is one of the most populated and urbanized regions characterized by a highly fragmented and diffuse landscape of urban and rural elements. Using 81 ponds in Flanders covering a gradient in urbanization we aimed to (1) estimate the relative importance of urbanization in explaining the variation in pond environment compared to other land use types (forest, nature, cropland, grassland); (2) assess at what spatial scale urbanization acts on and how this varies with spatial scale; and (3) how the importance of different land us types differs with spatial scale. The ponds were selected based on a unique hierarchical design in which urbanization levels (% build-up area around the pond for 50m radii up to 3200m radii) were uncorrelated at local and regional scale. For each pond we measured abiotic, biotic, and morphometric variables.
Results/Conclusions
RDA-based analyses show that although urbanization level explains only little of the environmental variation (0.17-1.35% explained, R²adjusted), it significantly affects pond environment, but only for urbanization levels determined at 50m up to 800m radii around the ponds. Pond substrate (artificial vs natural) confounded this pattern as there was a bias towards more artificial ponds located in local urban areas. For ponds with natural substrate (50 ponds), urbanization level significantly affected pond environment ranging from 400m up to 3200m radii, whereas no urbanization effect was detected for ponds with artificial substrate. Land use in general has a small but significant effect on pond environment, with percentage forest cover (R²adj: 1.42-4.82%) and built-up area (1.51-2.12%) being the main drivers. Forest cover has a significant effect on pond environment at all spatial scales and the effect increases with spatial scale, while percentage nature turns out to be important only at the local scale. This confirms the need for an integrated approach considering diverse spatial scales of urbanization and land use level.