Ecosystem Multifunctionality and Species Richness

Abstract

Ecosystem multifunctionality (EMF) -- the simultaneous provision of multiple ecosystem functions at high levels -- is increasingly recognised as the ecologically and practically relevant target for biodiversity conservation, because natural and human systems depend not on single functions in isolation but on the joint delivery of productivity, nutrient cycling, decomposition, water purification, carbon storage, pollination, and climate regulation simultaneously. Whether species richness promotes multifunctionality more strongly than it promotes any individual function -- the multifunctionality hypothesis -- is a central question in biodiversity-ecosystem function (BEF) research with direct implications for conservation investment decisions. This study provides the most comprehensive field-based test of the multifunctionality hypothesis yet published, measuring 18 ecosystem functions simultaneously at 247 grassland and woodland sites across 84 countries, combined with species richness, functional diversity, and phylogenetic diversity data. EMF (the proportion of functions simultaneously exceeding the 50th percentile threshold) showed a stronger positive relationship with species richness than any individual function (partial R2 = 0.67 for EMF vs. mean R2 = 0.38 for individual functions; p < 0.001 for the difference). The multifunctionality hypothesis is confirmed: biodiversity is more important for maintaining the simultaneous delivery of multiple functions than for any single function alone. Above a threshold of approximately 28.4 species per 100 m2 in grasslands, all 18 measured functions simultaneously exceeded the 50th percentile in 84.7% of sites -- demonstrating a practical species richness target for multifunctional ecosystem management.