How does biological diversity affect the way ecosystems function? Since the 1990’s, more than 500 experiments have address this question by experimentally manipulating the richness of species or functional groups and measuring how these aspects of biodiversity impact ecological processes like biomass production. Meta-analyses of these studies have shown that experimentally controlled systems with more biodiversity tend to be more efficient and productive than less diverse systems. But some have argued that experiments are too small in scale, too short in duration, and too unrealistic in conditions to be meaningful in the real world. They have hypothesized that, while biodiversity affects ecosystem processes in simplified experiments, similar effects are unlikely to occur in nature, or will be weak compared to the well-documented abiotic control of ecosystem productivity and stability. We tested this hypothesis with a synthesis of 128 empirical studies that measured biodiversity and biomass production at 581,160 sampling locations around the world while statistically controlling for environmental covariates. We used the synthesis to address three questions: (1) Are biodiversity effects on biomass production detectable in natural systems and, if so, are they consistent with results of experiments? (2) Are biodiversity effects in natural systems comparable in magnitude to those estimated in prior controlled experiments? (3) How do effects of biodiversity compare to effects of other major environmental drivers of ecosystem biomass production?
Results/Conclusions
Our synthesis shows that effects of biodiversity on biomass production in natural ecosystems are not only common, but are more (not less) likely to be statistically significant after controlling for environmental covariates. Without accounting for covariates, 67% of studies detected a significant relationship between biodiversity and ecosystem functioning, whereas among those that controlled for covariates, 81% were significant. Biodiversity effects in natural ecosystems proved to be stronger in magnitude than those documented in controlled experiments. In addition, biodiversity ranked higher in effect size than climate-related variables in 52% of field studies, and higher than nutrient-related variables in 60% of studies. So contrary to what has been proposed, biodiversity increases biomass production in a wide range of wild taxa and ecosystems and, after controlling for environmental covariates, biodiversity effects in nature are stronger than previously documented in experiments and comparable to or stronger than other well-known drivers of productivity including climate and nutrient availability. Our study confirms that changing biodiversity strongly affects the productivity of ecosystems in nature and should figure centrally in global change science and policy.