Integrating the Effects of Climate Change and Invasive Species on Wetland Ecohydrology to Evaluate Management Options

Abstract:

By the end of the century, temperatures in the North American Great Lakes region are predicted to 3-8°C warmer, and with seasonal precipitation response varying (0-25% annual increase). These changes will have profound effects on wetland hydrology in the region. At the same time, a dominant wetland type in the region, black ash (F. nigra) forested wetlands, is expected to lose much of its overstory canopy due to the invasive species Emerald Ash Borer (EAB). Field experiments focused on quantifying and reducing the ecohydrologic impact have been carried out for the last decade, showing persistent impacts to wetland hydrology. Due to the practical limitations of field experiments, these efforts have focused on mitigation under current hydrologic regimes. The loss of hydrologic stationarity requires that mitigation decisions consider altered wetland conditions in addition to assisted migration of potential replacement species. This study develops wetland water level and discharge models using seasonal climate and daily weather conditions. Separate models for forested and non-forested (EAB-impacted) wetlands allow comparison of potential conditions dependent upon management actions. Future climate scenarios are used to condition a stochastic weather generator (SWG) initially paramatized to local climatic conditions, providing inputs for wetland hydrology models. Simulated wetland hydrology including water levels, hydroperiod, inundated and dry spells, and wetland discharge are compared for forested and non-forested wetlands under present and future climates. Drier and warmer summer conditions, and a reduction in precipitation as snowfall are expected to be major drivers in changes to wetland hydrology. We hypothesize that wetland summer growing conditions within these wetlands will show fewer periods of inundation. We show that understanding changes in wetland hydrology due to climate change is important when planning mitigation for a separate impact, such as EAB.