Climatic implications for restoration of ecosystems on the Colorado Plateau under a changing climate

Background/Question/Methods

The ever increasing pressures applied to ecosystems on the Colorado Plateau, in particular changes in land use and anthropogenic forced changes in climate, appear to be degrading these systems toward “thresholds” that may not be re-traversed once crossed. Observed examples of ecological change, such as the increased probability and duration of wildfires, insect outbreaks with concurrent widespread tree mortality, and changes in vegetation ecotones, have occurred over much of the western United States and have been attributed to changes in temperature and precipitation regimes. Recent studies have shown changes in winter temperature maximum and minimum and the hydrological cycle of the western United States are outside of what would be expected from natural variability. Thus, these observations suggest that natural climatic cycles (i.e. Pacific Decadal Oscillation, El Niño Southern Oscillation, etc.) are acting synergistically with underlying climatic trends associated with increased greenhouse gas forcings. Of particular importance for the Colorado Plateau, future warming may alter the position and strength of the North American Monsoon (NAM), which is responsible for a sharp summertime moisture gradient across the region. Natural resource managers, therefore, are faced with unprecedented challenges if these trends continue. In this paper we analyze historical daily climate records to quantify and compare the current and historical spatio-temporal pattern of precipitation across the Colorado Plateau, describe the variability of seasonal precipitation in the northern limits of the NAM region, and discuss the influence of future warming on the hydrological regime of the Colorado Plateau.

Results/Conclusions

Our results show that a focus on the variability and pattern change in extreme climate anomalies, rather than in the mean state, is vital to inform the decision-making process in the management of natural resources and planning of restoration programs. Specifically, key climate variables such as inter- and intra-annual temperature maxima or minima, seasonality of both temperature and precipitation patterns, as well as interactions with multi-decadal cycles trends driven by large scale climate dynamics, need to be considered. This is analyzed through a set of fine-resolution climatic data of daily temperature and precipitation, as well as regional climate model output at a coarser resolution. Additionally, policies that guide management action into the future should be based on adaptive strategies that cover a wide range of plausible climatic conditions.