water Editorial Land Use, Climate, and Water Resources—Global Stages of Interaction Sujay S. Kaushal 1,*, Arthur J. Gold 2 ID and Paul M. Mayer 3 1 Department of Geology & Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD 20740, USA 2 Department of Natural Resources Science, University of Rhode Island, Kingston, RI 02881, USA; [email protected] 3 National Health and Environmental Effects Research Lab, Western Ecology Division, US Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR 97333, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-301-405-7048 Received: 13 September 2017; Accepted: 19 October 2017; Published: 24 October 2017 Abstract: Land use and climate change can accelerate the depletion of freshwater resources that support humans and ecosystem services on a global scale. Here, we briefly review studies from around the world, and highlight those in this special issue. We identify stages that characterize increasing interaction between land use and climate change. During the first stage, hydrologic modifications and the built environment amplify overland flow via processes associated with runoff-dominated ecosystems (e.g., soil compaction, impervious surface cover, drainage, and channelization). During the second stage, changes in water storage impact the capacity of ecosystems to buffer extremes in water quantity and quality (e.g., either losses in snowpack, wetlands, and groundwater recharge or gains in water and nutrient storage behind dams in reservoirs). During the third stage, extremes in water quantity and quality contribute to losses in ecosystem services and water security (e.g., clean drinking water, flood mitigation, and habitat availability). During the final stage, management and restoration strategies attempt to regain lost ecosystem structure, function, and services but need to adapt to climate change. By anticipating the increasing interaction between land use and climate change, intervention points can be identified, and management strategies can be adjusted to improve outcomes for realistic expectations. Overall, global water security cannot be adequately restored without considering an increasing interaction between land use and climate change across progressive stages and our ever-increasing human domination of the water cycle from degradation to ecosystem restoration. Keywords: land use; climate; urbanization; agriculture; dams; stream burial; urban evolution; salinization; Anthropocene; stream restoration; best management practices; models 1. The Emerging Global Water Crisis Over 75% of Earth’s land surface has now been impacted by human development [1], which exerts an expanding footprint on water resources. There are distinct patterns in the evolution of land use change [2,3], and land use is a template on which climate interacts to influence the quantity and quality of Earth’s water [4]. In order to support human-dominated land use, ground water in semi-arid and arid landscapes has been decreasing by approximately 150 cubic km per year due to increasing extraction [5] (and references there in). Water stored as ice on land, which is critical for major drinking water supplies, has decreased at a rate of approximately 300 cubic km per year due to warming and changes in regional precipitation patterns [5] (and references there in). In fact, access to clean water is considered one of the contemporary grand challenges for engineering by the U.S. National Academy of Engineering (http://www.engineeringchallenges.org/challenges/water.aspx). 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