Decline of Common Toad Populations in Flanders Is Not Linked to Surrounding Landscape

Despite their significance in ecosystems, the decline of common species receives little attention in conservation. Identifying the underlying drivers of common species declines is necessary to mitigate further biodiversity loss. Common Toads (Bufo bufo) in Europe are emblematic of a once common species that is presumedly undergoing widespread declines. We aim to quantify population trends of Common Toad in Flanders and assess to which extent population trends depend on general landscape variables (land use identity, structure and change). Using standardised time series obtained from citizen science and spanning over four decades, we used an end-begin contrast to get a trend value for 234 populations. Next, we developed a testing strategy to find associations between these trend values and the surrounding landscape. Across the study region, 40% of the populations have declined significantly, while only 10% show an increase. Declines were not associated with landscape characteristics in our study area, which is one of the most fragmented regions in Europe. We discuss how the research region, spatial and temporal resolution, as well as the generalist nature of the species, may explain these findings. Our study suggests limited effects of general landscape characteristics on the decline of Common Toad populations, indicating that other major drivers are likely responsible.