Meadow harvesting techniques and their impacts on field fauna

Meadows require regular harvesting (cutting) to avoid vegetation succession, and this is well known to promote high plant diversity. The impacts of the harvesting process on animal, and particularly invertebrate, abundance and diversity is not, however, well known, but is expected to be largely negative. This study reviews the available information on the direct mortality caused by the meadow harvesting process on vertebrate and invertebrate populations with the intention of raising the profile of this neglected area of research which is nevertheless important in the context of declining field fauna diversity. Collectively, the studies show a direct and often substantial impact of the harvesting process on the fauna, especially from the mowing stages, and that this impact depends on the techniques and equipment used, as well as the settings, the habitat and the ecology of each species. The post-mowing harvesting stages also have considerable relevance, especially grass removal (baling), which may first concentrate organisms in windrows before removing them from the field, but have been rarely studied. Differences among mowing techniques and equipment can amount to a threefold change in the scale of impact on field fauna, and therefore there is a potential to reduce direct harvesting impacts. According to the reviewed studies, the use of cutter bar mowers is recommended over rotary and flail mowers, as they cause half as much mortality. If a rotary mower is used, then an add-on conditioner should be avoided. However, for less mobile species, it is still unclear if the benefit gain from friendly mowing techniques might be cancelled by subsequent harvesting stages, and this important point needs further investigation. Because no practicable harvesting processes are damage free, leaving uncut grass strips is a simple and good practice that will benefit many organisms.