Direct and terrestrial vegetation-mediated effects of environmental change on aquatic ecosystem processes

Global environmental changes have direct effects on aquatic ecosystems, as well as indirect effects through alterations of adjacent terrestrial ecosystem structure and functioning. For example, shifts in terrestrial vegetation communities resulting from global changes can affect the quantity and quality of water, organic matter, and nutrient inputs to aquatic ecosystems. The relative importance of these direct and terrestrial-vegetation-mediated effects is largely unknown, but understanding them is essential to our ability to predict the consequences of global changes for aquatic ecosystems. Here, we present a conceptual framework for considering the relative strengths of these effects and use case studies from xeric, wet and temperate, and boreal ecosystems to demonstrate that the responses of aquatic ecosystems to drivers of global changes may not be evident when the pathways are studied separately. Future studies examining changes in aquatic ecosystem structure and functioning should consider the relative contributions of both direct and terrestrial-vegetation- mediated effects of global changes.