Expert-based modeling approach for assessing the effect of agricultural management measures on amphibian migration

 

The decrease of available habitat patches as well as habitat fragmentation and environmental pollution by agricultural chemicals are among the major causes for the observed global amphibian decline. The fragmentation of suitable habitat patches is mainly driven by the increase of agricultural areas, which represents the dominant human land use. In addition, roads and railways may affect local amphibian population viability by reducing and isolating suitable habitat patches. Moreover, landscape elements (e. g. flowing waters and hedges) and human activities (e. g. mowing and harvesting) may also affect amphibian migration and occupancy of habitat.


Pond breeding amphibian populations operate at multiple scales, from the individual breeding pond over surrounding habitat patches to clusters of breeding pond populations. The connectivity among breeding ponds as well as the availability of suitable terrestrial habitats surrounding breeding ponds plays a major role in long-term viability of amphibian species. Besides road traffic also agricultural land use can disrupt this connectivity due to pesticides, fertilizers and tillage operations. In the vineyards of Palatinate (Rhineland-Palatinate, Germany) pesticide applications are conducted during immigration and emigration of adult amphibians as well as the emerging of juveniles.

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Therefore we developed an expert-based model to assess the impact of agricultural management measures on the migration area and terrestrial habitat availability for seven endemic amphibian species. The model includes a habitat suitability index approach to identify potential terrestrial habitats and a landscape permeability approach to take landscape permeability into account. Landscape permeability and migration distances for the investigated species were derived from scientific literature with relevance to the study area. The disrupting effects of agricultural management measures were simulated by increasing the landscape resistance of vineyards, which is the dominant land use within the study area. Size of migration areas, connectivity of breeding ponds and number of reachable terrestrial habitats were modeled for three scenarios. Highest decrease of migration areas and reachable terrestrial habitats was measured for Rana dalmatina whereas Bufo bufo and Lissotriton vulgaris had the least decrease.


Contact

Patrick Lenhardt
Dr. Carsten Brühl

Related Publications

  • Patrick Lenhardt & Carsten A. Brühl (2010): Modellbasierte Abschätzung der potenziellen PSM-Exposition adulter Amphibien in der Agrarlandschaft (Weinbaugebiet Südpfalz). 4th joint Annual Meeting of the SETAC GLB and GDCh (Section Environmental chemistry and Ecotoxicology) 2010, Dessau, Germany (more Info)