Rapid biodiversity assessment of arthropods for monitoring average local species richness and related ecosystem services

Rapid biodiversity assessment (RBA) is proposed as an affordable indicator for monitoring local species richness of arthropods and sustainability of related ecosystem services. The indicator is based on strictly standardised sampling procedures and the identification of parataxonomic units (morphospecies) instead of species identification. The collection of arthropods was optimized with regard to trap types, time and length of collecting period, selection of four out of seven weekly samples, and choice of counted taxa and trophic guilds. By measuring arthropod activity, RBA is an indicator for functional diversity. Over a period of 8 years, average yearly numbers of morphospecies were assessed in Switzerland in 15 agricultural habitats, 15 managed forests, and in 12 unmanaged habitats ranging from protected lowland wetlands to Alpine meadows. The yearly RBA-trend in unmanaged habitats is used for assessing the influence of climate and weather on biodiversity, and as a reference for measuring the relative influences of recent management changes in agriculture and forestry. The average number of morphospecies per sampling station per year depends on temperature, and was only marginally significantly increasing over time in agriculture, but not in forestry or unmanaged areas. Three RBA indices considered to be relevant for maintaining ecosystem services were calculated from the average number of morphospecies per location per year: (1) indicator for ecological resilience and sustainability (all morphospecies); (2) indicator for pollinator diversity (taxa with a majority of pollinators) and (3) indicator for biocontrol diversity (ratio between carnivore and herbivore guilds).