Can agri-environmental schemes enhance non-target species? Effects of sown wildflower fields on the common hamster (Cricetus cricetus) at local and landscape scales

During the last decades, agriculture has been rapidly intensified, resulting in a strong decline in species diversity. Therefore the common agricultural policy (CAP) of the EU implemented agri-environmental schemes (AES) for an environmentally-friendly management of agricultural areas. Sown wildflower fields are one of these measures aimed at enhancing insect diversity and related ecosystem services. However, little is known about the impacts of AES on rare and non-target species. To study the effect of these AES on a non-target species, the occurrence of the endangered common hamster (Cricetus cricetus) was mapped by counting reopened winter burrows on paired sown wildflower fields and agricultural fields in North-West Bavaria, Germany. Concentration effects in sown wildflower fields and the distribution of C. cricetus in adjacent agricultural fields were studied by mapping burrows up to a distance of 200 m from sown wildflower and agricultural fields. Furthermore, C. cricetus occurrence in relation to local (vegetation density, cover of grasses, vegetation height, size of wildflower fields) and landscape scale parameters (percentage of arable land, grassland, fallow land, distance to the nearest forest, and settlement) of sown wildflower fields was analysed. Results show that there was a concentration of C. cricetus in sown wildflower fields, while densities in adjacent agricultural fields were constantly low. Hamster occurrence was negatively related to vegetation density and grass cover on sown wildflower fields and positively related to distance to the nearest forests, percentage of arable land and fallow land around wildflower fields. In conclusion, we could show that sown wildflower fields can be an ideal habitat for non-target species, such as the common hamster. However, local and landscape scale parameters of sown wildflower fields need to be considered when designing AES.