Indicators of pollinator decline and pollen limitation

Pollination is a crucial process for maintaining plant reproduction, and is responsible to the yield of about two third of the world’s crops. In recent years, there are growing concerns over pollinator declines and global pollination crisis. A decrease in pollinator populations also affects plants’ reproductive success, and alters the composition of wild plant communities. The main drivers for pollination decline are agriculture intensification and the subsequent fragmentation and loss of habitats, as well as introduction of non-native species and indirect effects of global climate change. Specialist pollinators and self-incompatible plants are seemingly in higher vulnerability. Our current knowledge of environmental effects on pollination processes is limited by the relatively little knowledge of the ecological requirements of pollinators and plants, and by the shortage of studies on the response of populations and communities to changes in land use. In this chapter we provide indices for estimating pollinator decline in both local and landscape scale, and discuss the relative efficiency of taxonomic and environmental indicators and indicators for estimating pollination services. We propose that future research should include developing and testing cost-effectiveness of indicators for patterns of pollinators’ diversity and of indicators for pollination services. These indicators should be tested in various ecological and spatial scales.