Climate change assessment using spatial climate datasets: Theodore Roosevelt National Park (South Unit), 1895-2019

Abstract

Climate change poses a major challenge to park managers of the United States National Park Service. Several studies have surveyed system-wide climate change, but limited funds prevent the development of local-scale climate change studies. We examined climate change at Theodore Roosevelt National Park (South Unit) in Medora, North Dakota (USA), using spatial climate datasets. We surveyed the period 1895-2019 to provide a long-term perspective, and more closely analyzed the period 1960-2019, when the quality assurance of the database was highest, concerns over anthropogenic climate change effects were greatest, and relevance to current management was most critical. Our results show moderate changes over the past 60 yr. Interannual and decadal-scale climatic variation dominated long-term climate and weakened the statistical significance of most long-term climate trends. The most pronounced changes were an increase in mean annual minimum air temperature and a decrease in mean annual diurnal temperature range. Mean annual precipitation showed a small increase, while an increase in fall precipitation was the most pronounced seasonal precipitation change. Estimated snow water equivalent and snow fraction increased slightly. Climatic water balance results indicate an increase in mean annual soil moisture storage and annual moisture index. Vegetation growing season changes include an increase in the frost-free season length but a decrease in the length of the thermal growing season. The sign and magnitude of change of individual climate variables is sensitive to the period of record examined. Study results provide a baseline for park managers to assess climate change impacts upon grassland productivity, wildfire hazard, and invasive species, and reveal an opportunity to lengthen the tourism season in this summer peak tourism climate.