Impacts of regenerative agriculture on biodiversity: does ‘mob-grazing’ benefit moths?

Abstract

Moths are highly diverse and provide essential pollination services and food for higher taxonomic groups. Grassland moth species that rely on extensive grassland management are in decline across Europe, likely due to intensive farming practices and associated high livestock stocking rates. However, reducing stocking rates may be detrimental to farmer livelihoods. ‘Mob grazing’, a type of rotational grazing, aims to mimic the grazing behaviour of wild megaherbivores by increasing pasture rest periods whilst maintaining large herds of cattle and is gaining popularity across different continents. This practice is often marketed as being beneficial for biodiversity, but there is limited scientific evidence supporting this. We investigate whether mob grazing cattle is beneficial for moths in comparison to more widespread ‘set-stock’ grazing systems. We measured abundance and species richness of moths in thirteen mob grazed fields and thirteen set-stock fields across Scotland (United Kingdom). We did not detect any direct effect of mob grazing on moths in either larval or adult forms. However, mob grazing mitigated the negative effect of sheep grazing on caterpillar abundance and species richness, likely by reducing overall grazing pressure through longer pasture rest periods. Caterpillar abundance and species richness decreased with increasing grazing intensity. Lower caterpillar abundance was also associated with high cover of ryegrass (Lolium spp), a grass species that is indicative of intensively managed pastures. To our knowledge, this is the first time that the effects of mob grazing on moths have been explored. Our findings suggest that mob grazing can reduce pressure on moths whilst enabling farmers to maintain higher numbers of cattle.