Accounting for functional diversity in biodiversity protection measures

Societal Impact Statement: Globally, countries are becoming increasingly committed to conserving biodiversity. Traditional methods of measuring biodiversity are simple and might miss out on capturing some of the more important functional features that comprise ecosystems. We compare a real-world conservation program with background vegetation data to explore whether these traditional methods sufficiently capture the diversity of the forms and functions of plants. Our results suggest that there is a great opportunity to broaden our definition of biodiversity to include these functional metrics in our conservation planning, which would improve the representativeness of protected areas. Summary: Functional diversity (FD) is a widely used metric in ecology that captures aspects of biodiversity complementary to species richness, although it is not commonly used in conservation. Conservation programs with broad aims to protect biodiversity could use FD to better monitor their progress alongside conventional species richness-based metrics. This study investigates how FD is captured in a large-scale private conservation network, relative to commonly used taxonomic metrics. We combined floristic data from 36,711 vegetation plots composed of two plot networks (private and background) in southeastern Australia, with species-level trait information on leaves, height, stems, and seeds. We compared species richness and an existing diversity metric used in management with functional richness, evenness, and dispersion across plot networks. Further, we compared individual trait values between plot networks and use hypervolumes to compare functional overlap of trait space. Despite higher species richness in private conservation plots, functional richness, evenness, and dispersion were all lower than in background plots. Functional hypervolume analysis showed that private conservation plots captured only 43.7% of the functional space represented in background plots. Differences in plant height, leaf mass per area, and leaf nitrogen content suggest that the private network is characterized by slow economic strategies. We show that important dimensions of biodiversity can be overlooked in conservation programs that do not account for other facets of biological diversity. Integrating FD into conservation monitoring and planning will provide another useful tool for capturing the diversity and function of life, ultimately leading to more effective and representative conservation programs.