U.S. NATIONAL PARK SERVICE: MANAGING WITHIN A LANDSCAPE OF DYNAMIC HYDROLOGICAL SYSTEMS FUELED BY A CHANGING CLIMATE

Rising temperatures associated with climate change will influence many aspects of the hydrological systems in U.S. national parks. Salt water intrusion to coastal freshwater aquifers due to sea-level rise; increase in jökulhlaups in Alaska due to warming; loss of cold-water trout habitat in the U.S. interior West; and increase in coral bleaching in the Caribbean are just a sample of the challenges that park managers are either facing now or will face in the 21^stCentury.

The average annual temperature in the U.S. has increased by 1.3° to 1.9° F since 1895, with most of this increase occurring since 1970. Average annual temperature in the Arctic has risen by almost twice the global rate over the past few decades. Temperatures in the U.S. are expected to continue to rise, further expanding the management challenges. Warmer surface temperatures will increase evaporation from the oceans and inland freshwater systems, which in turn increases globally averaged precipitation. Greater energy in the atmosphere due to warming can strengthen storms and change frequencies and timing, though these changes are difficult to model into the future. Rising temperatures have reduced lake ice, sea ice, glaciers, permafrost, and seasonal snow cover across the U.S. the past few decades. As the average annual temperature increases, sea level also rises due to ocean water expansion as it warms and contributions from melting glaciers and ice sheets. Oceans are also becoming more acidic as they continue to absorb the human-caused carbon dioxide.

So how does the U.S. National Park Service manage within these dynamic hydrological systems fueled by a changing climate? How do you identify what climate future to plan for? These are not easy questions to answer and can sometimes be overwhelming. Or, if structured correctly, can stimulate new ways of thinking and planning.

Scenario planning is a living process selected by the U.S. National Park Service to plan and manage into the uncertain future of climate change. Through this process, managers and others develop science-based scenarios of the future that incorporate plausible changes in climate and other key variables. These are used as a basis for identifying potential strategies to address future challenges to important resources and values, including the hydrological systems in U.S. national parks.