The fate of amphibians in Aargau: effect of future land-use scenarios
Roth, L., 2021: The fate of amphibians in Aargau: effect of future land-use scenarios. Master thesis. 50 p.
Roth, L. (2021): The fate of amphibians in Aargau: effect of future land-use scenarios. Master Thesis ETHZ, D-USYS. Supervisors: PD Dr. J. Bolliger, Dr. G. Donati.
Biodiversity is essential to sustain various ecosystem services. The growing human population and associated land-use change through urbanization and intensification of agriculture result in degradation, loss, and isolation of habitats. Largely due to this land-use change, 40 % of amphibian species are considered to decline worldwide. The concept of Blue-Green Infrastructure (BGI) aims to alleviate conflicts between human and natural ecosystems. In this study, occurrences of 10 amphibian species with differing habitat requirements in the Canton of Aargau were modelled. With the aid of these species distribution models, the influence of five future land-use scenarios, which differed regarding human population growth and the degree of governmental interventions, was assessed. Two existing landscape inventories supporting biodiversity were regarded as starting points to identify regions with existing and missing BGI coverage. My findings revealed that scenarios with a higher degree of urbanization resulted in a higher change of modelled biodiversity hotspot areas, which resulted not only in losses but also in gains. The results suggest that gains on future urban areas can occur provided that the surrounding coverage within a focal window of 300 x 300 m remains on average below 70 % regarding urban land use and above 20 % concerning forest coverage. As urbanization in the included land-use scenarios is mostly predicted in flat areas near the main rivers of the Canton encompassing primary habitats for many amphibian species, biodiversity hotspot losses were mostly predicted in these areas. Therefore, a continuation of the displacement of amphibians into secondary habitats was predicted. As habitat requirements vary severely between amphibian species, BGI needs to be planned and managed as diversely as possible. For instance, the comparison of the two species with the most extreme predicted future changes suggested that Epidalea calamita might establish in urban areas, while Salamandra salamandra probably profits more from consistent protection of forests. This underlines the importance of deriving BGI in both urban and rural environments. 18 % of the modelled amphibian biodiversity hotspot areas in the study area resulted to be covered by existing landscape inventories with legally binding protection goals and can be regarded as already having a network of BGI. However, other regions like the Southwest of the Canton of Aargau, where additionally several models agreed on predicting biodiversity loss, were found to lack coverage. To sustain biodiversity and associated ecosystem services in the long-term, this finding could support decisions for additional legally binding conservation strategies in these areas.