What is biodiversity's role in providing ecosystem goods and services? A data synthesis

Background/Question/Methods

The idea that ecosystems provide goods and services to humanity has become a prominent theme in the scientific and popular literature.  With the rise of this theme, there have been an increasing number of claims that biodiversity is required to maintain ecosystem goods and services.  But even a cursory review of the literature suggests that many of these claims have been based solely on expert opinion.  And often times, the work cited as evidence has more to do with the presence/absence of entire ecosystems or groups of organisms than diversity per se (e.g., impact of mangrove forests on flood protection, or of all native pollinators on pollination).

To assess the validity of proliferating claims, we performed a literature review to identify and summarize the results of primary data papers linking biodiversity per se (variation in genes, species, or functional traits) to ecosystem services.  Based on this review, we draw three conclusions: 

Results/Conclusions

First, there is sufficient data to show that biodiversity per se either directly influences (experimental data), or is strongly correlated with (observational data), ca. one-third of the ecosystem services reviewed.  These include the production of fodder, yield of some commercially important crops, production of wood, stability of fisheries, resistance to invasive species, and the prevalence of select plant pathogens.

Second, for 61% of the ecosystem services reviewed, the available evidence is either decidedly mixed, or there is insufficient data to characterize the relationship between biodiversity and the proposed service.  Noteworthy examples include the impacts of plant diversity on long-term carbon storage, effects of vertebrate host diversity on the prevalence of disease, and effects of biodiversity on flood regulation - all of which has been extensively cited in the literature as a direct product of biodiversity. 

Lastly, for a few services, the current evidence runs counter to expectations, illustrating that biodiversity can, in some instances, produce the opposite of the service we desire.

Our synthesis is both good news and bad.  The good news is that real data is, in fact, accumulating.  We are in position to start drawing direct causal linkages between biodiversity per se and certain goods and services that ecosystems provide to humanity.  The bad news is that claims appear to outweigh available data, which suggests we need to be cautious about the possibility of unsubstantiated conclusions in the literature.