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Interacting Effects of the Invasive Emerald Ash Borer and Climate Change on Forested Wetland Hydrology

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Monday, January 31, 2022, 3 pm

This is a past event.

Environmental Engineering Graduate Seminar

Joe Shannon, PhD, Data Scientist, NCX


Wetlands around the globe are already being impacted by changing temperature and precipitation patterns. Simultaneously black ash forested wetlands are expected to lose much of their overstory canopy due to the invasive insect Emerald Ash Borer (EAB). Field experiments and modeling efforts have provided information on species tolerance of post-EAB conditions and future climate adapted species. No studies have yet examined the interaction of the loss of ash and future climate scenarios on wetland conditions. I developed daily water level models for three wetland canopy conditions: ash forest, non-ash forest, and herbaceous/shrub. Modeled simulations were evaluated under current climate conditions and under two future climate scenarios representing warmer/drier or hotter/wetter conditions. For each canopy-climate combination, 10,000 annual synthetic weather sequences were used as inputs to the water level models. Weather sequences were generated using stochastic weather generators conditioned on 30 years of daily projections using localized constructed analog-downscaled global climate model outputs. Simulated wetland hydrology remained highly variable based on seasonal precipitation and evaporative demand. I compared to the probability of exceeding certain water level thresholds, which represent water level drawdown, surface inundation, and stream-network connectivity. As conditions become drier and warmer, inundation and connectivity become less common, and drawdown increases. Our results present the total impact of the interaction of vegetation and climate change as well as the individual impact for each driver. For non-ash forests, wetland drawdown is increased under future climate conditions compared to ash forests and herbaceous/shrub cover. Simulated non-ash forests were assumed to be less flood adapted than black ash, simulated with lower transpiration rates under inundated conditions. Our simulations suggest persistently wetter wetland conditions under these forests. Replacing black ash forests with non-ash forests has as the same magnitude impact on future hydrology as simulated climate change impacts under both scenarios evaluated. The impact of transitioning to herbaceous/shrub cover has smaller magnitude impact than that of climate change. Both alternative vegetation covers led to wetter conditions relative to black ash, while both potential climate scenarios resulted in drier conditions. Our results show that the interaction of climate change and EAB could result in a canceling effect with each change mitigating the severity of the other. These findings provide insight into the interaction of two common threats to forest ecosystems and can be used to guide management approaches on the landscape.

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