Conceptual model for direct and indirect effects of global changes on biodiversity. Shown are effects on ecosystem biodiversity from elevated nitrogen, CO2 and climate change (elevated temperature and changes in precipitation and hydrology). Predominant direction of effect is shown as positive (+), negative (-) or as a possible change in either direction (∆). Changes in nitrogen, CO2 and climate can influence biodiversity. Nitrogen and CO2 also can interact with climate to effect on biodiversity (Porter et al., 2013).