Two of the most pervasive human impacts on ecosystems are alteration of global nutrient budgets and changes in the abundance and identity of consumers. Fossil fuel combustion and agricultural fertilization have doubled and quintupled, respectively, global pools of nitrogen and phosphorus relative to pre-industrial levels. Concurrently, habitat loss and degradation and selective hunting and fishing disproportionately remove consumers from food webs. At the same time, humans are adding consumers to food webs for endpoints such as conservation, recreation, and agriculture, as well as accidental introductions of invasive consumer species. In spite of the global impacts of these human activities, there have been no globally coordinated experiments to quantify the general impacts on ecological systems. The Nutrient Network (NutNet) is a grassroots research effort to address these questions within a coordinated research network comprised of more than 140 grassland sites worldwide.

NutNet focal research questions:

1. How general is our current understanding of productivity-diversity relationships?
2. To what extent are plant production and diversity co-limited by multiple nutrients in herbaceous-dominated communities?
3. Under what conditions do grazers or fertilization control plant biomass, diversity, and composition?

NutNet goals:

1. To collect data from a broad range of sites in a consistent manner to allow direct comparisons of environment-productivity-diversity relationships among systems around the world. This is currently occurring at each site in the network and, when these data are compiled, will allow us to provide new insights into several important, unanswered questions in ecology.
2. To implement a cross-site experiment requiring only nominal investment of time and resources by each investigator, but quantifying community and ecosystem responses in a wide range of herbaceous-dominated ecosystems (i.e., desert grasslands to arctic tundra).