Ecosystem services: The disproportionate value of individual species in biological cold-spots

Background/Question/Methods

The ecosystem services provided by biodiversity have been the subject of intensive ongoing study for many years. While many important aspects of ecosystem functioning have been elucidated, there has been little effort to consider the biogeographical context of this work. Here we ask whether individual experiments on biodiversity and ecosystem functioning can be better understood by considering the geographic and climatic context of this work. To consider this we draw on a recent review article that reports the Relative Yield Total (RYT) values for 19 biodiversity/ecosystem functioning experiments conducted in plant communities of Europe and North America. We analyzed whether RYT values can be better understood by considering the physical and climate characteristics of the sites in which these experiments were conducted. Specifically we examined the following physical variables: latitude, longitude, elevation, as well as more than a dozen climatic variables, such as annual mean temperature, maximum temperature of the warmest month, and annual precipitation. We analyzed the relationship between RYT and these variables using pair-wise comparisons. We also performed stepwise multiple linear regression analyses with these data. 

Results/Conclusions

We find that physical and climatic variables are strong predictors of the RYT results found in plant experiments across Europe and North America. There is a strong positive relationship between RYT and latitude. Climate is also a strong predictor of RYT; e.g., there is a strong negative correlation between RYT and annual mean temperature, which explains more than 50% of the variation across sites. A multiple linear regression explains more than 60% of the variation across sites. The robustness of these results in surprising given the disparate protocols used in the different experiments that comprise this data set. These results indicate that RYT is strongly influenced by site location. Sites at higher latitudes, where conditions are colder and more extreme climatically have much higher RYT values. This could be due to greater niche-complimentarity or facilitation among species in such environments. Regardless of the mechanism, this result implies that species loss (of even a single species) from cold, high-latitude, and generally species-poor environments will have large disproportionate impacts on ecosystem functioning. In turn, this suggests that species-poor “cold-spots” of biological diversity are more important to protect than previously appreciated if we are going to safe-guard the provisioning of ecosystem services.