Impact of different meadow mowing techniques on field invertebrates

Low-input meadows are now recognized for their high biodiversity value and form an integral element of many agri-environmental schemes in Europe. Meadow mowing techniques, however, have become highly mechanized in recent decades and scientific knowledge on the direct impacts of these techniques on field fauna is based on very few and often poorly replicated studies. Yet these studies, despite their limitations, suggest that such impacts can be considerable. With a view to providing a more comprehensive experimental assessment, we evaluated the direct impacts of four different mowing techniques (hand motor mower with cutter bar, rotary mower cut at 9 cm and rotary mower cut at 6 cm with and without a conditioner) on wax invertebrate models and real caterpillars. The size of the organisms, their microhabitat, the tractor wheel effect and the cutting height were also investigated as factors that could potentially affect mowing-caused mortality. Rotary mowers were found to be more damaging than motor bar mowers on caterpillars (37% vs. 20%), but only on one type of invertebrate wax-model. Conditioners more than doubled damage to all wax-models in the vegetation (in average from 11% to 30%) and increased caterpillar mortality from 38% to 69%. Larger organisms were more vulnerable than smaller organisms and ground organisms were strongly impacted by tractor wheels. While conditioner should not be used in meadows where conservation of the inhabiting fauna is of concern, we also recognize that there is no damage-free mowing technique. We therefore advocate the importance of leaving uncut areas as a refuge for invertebrates.