The Nutrient Network: Grassroots Science to Address Global-Scale Environmental Change

Among the greatest challenges for ecology in the current decade is developing a predictive understanding of the links between species interactions, biodiversity, and ecosystem function, on one hand, and global-scale anthropogenic perturbations to species distributions and nutrient and carbon cycles, on the other.  In particular, while these grand challenges lie at the global scale, a predictive understanding of ecosystem functioning requires experimental work at the local scales of individuals and species interactions.  Although many important tools can provide insights into the effects of human perturbations on biodiversity and ecosystem functioning, including single-site experiments, mathematical models, observational networks, and meta-analysis, each has clear limitations for developing globally relevant predictions.  Whereas distributed networks are not a new idea, global-scale collaborative experiments designed and run by experts are relatively novel.  These hold the potential to bridge the gap between site-scale experiments and global-scale predictions. We are using this approach to address relevant, general ecological questions in the grasslands of the world.  Like other ecosystems, our understanding of grassland responses to anthropogenic perturbations comes primarily from site-scale studies, analytical models, and a few meta-analyses.  I will discuss my group’s experience with conceiving and implementing a distributed network of identically-replicated grassland experiments to examine a variety of questions of broad scientific relevance. 

The 67 sites distributed across 6 continents that are currently participating in this distributed experiment represent much of the natural range of global grassland diversity and productivity, with sites including salt marsh, mesic grassland, desert grassland, savanna, montane meadows, and alpine tundra.   We are addressing our core questions with these data, but the diversity of participating researchers and unparalleled experimental data also is creating substantial scientific synergy which is leading us to ask and answer questions we did not originally foresee.  Using directly comparable experimental data from all of these habitats, investigators across the network are addressing globally-relevant ecological problems, including the generality of relationships between ecosystem productivity and biological diversity, the effect of ambient nitrogen deposition on the world’s grasslands, the effects of single and combined nutrients on grassland communities, and the biogeographic patterns of species invasions.