Impacts of Global Change Scenarios on Ecosystem Services from the World's Rivers

Water is an essential building block of the Earth system and is critical to human prosperity. At the same time, humans are rapidly embedding themselves into the basic character of the water cycle without full knowledge of the consequences. Major sources of water system change include mismanagement and overuse, river flow distortion, pollution, watershed disturbance, invasive species, and greenhouse warming. A pandemic syndrome of risk to rivers-the chief renewable water supply supporting humans and aquatic biodiversity—is evident at the fully global scale, with a costly price-tag ($0.5Tr/yr) required for engineering-based management solutions aimed at fixing rather than preventing problems before they arise. A new project funded under the NSF's Coupled Natural-Human Systems program aims to improve our current understanding of the geography of water-related ecosystem services, accounting for both biophysical and economic controls on these services, and assessing how new management strategies could enhance the resiliency of the global water system over a 100-year time horizon. Within the context of the many sources of threat summarized above, we see the coupling of human-natural systems to be intrinsic to the science at hand, through which we have formulated our central hypothesis: Human-derived stresses imposed on the global water system will intensify over the 21st century, reducing water-related freshwater ecosystem provisioning and supporting services, increasing the costs of their remediation, limiting and shifting the geography of key economic sector outputs, and threatening biodiversity. Addressing this hypothesis has forced a substantial advancement in current capabilities, namely to (i) extend analysis into the 21st century through scenarios, (ii) develop explicit links to freshwater ecosystem services, (iii) assess how the condition of ecosystem services influences the world economy through individual sectors (food, energy, domestic water supply, fisheries), and global trade, and (iv) identify critical thresholds, constraints, and feedbacks, and consider tradeoffs that could reduce emerging water resource constraints, preserve ecosystem services, and yield economic benefits in the future economy. The talk summarizes a strategy for realizing these advancements and presents a series of early results.