HGS RESEARCH HIGHLIGHT – Potential influence of climate change on ecosystems within the Boreal Plains of Alberta
Thompson, C., Mendoza, C. A., & Devito, K. J. (2017). Potential influence of climate change on ecosystems within the Boreal Plains of Alberta. In Hydrological Processes (Vol. 31, Issue 11, pp. 2110–2124). Wiley. https://doi.org/10.1002/hyp.11183
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This paper by researchers at the University of Alberta discusses the possible impacts of climate change in the Boreal Plains in Northern Alberta, Canada. The sensitive ecosystems in this area have developed under a delicate water balance, while climate change and warming temperatures threaten to shift water availability. This study looks at ponds, peatlands with sparse black spruce, and hillslopes with predominantly aspen forests as the features of focus. A previously calibrated 2-dimensional HydroGeoSphere model encompassed these different ecosystems to simulate 13 climate scenarios from 2011 – 2090. The results were compared to a simulation with no climate change impacts, the base case scenario. In each simulation precipitation fluxes and evapotranspiration were applied daily using the adaptive time-stepping scheme available in HGS. By simulating a wide range of climate scenarios the authors hoped to evaluate how climate change will influence interactions between these ecosystems, whether peatland ecosystems will suffer from a decline in water levels and how this will impact surface water features (e.g. will lakes/ponds remain permanent features, or become ephemeral), and whether sufficient water will be available to sustain forests and prevent the northward migration of prairie grasslands. The authors noted that there are many factors in addition to climate change that could impact these ecosystems and so further research is needed.
The subhumid climate of the Boreal Plains is normally ideal for these ecosystems to thrive but the warmer temperatures (up to 2 to 5C hotter) and overall decreased summer precipitation threaten their long-term sustainability. The simulations suggest that peatland water levels could decrease up to 1m, making them more susceptible to wildfires, pests, and diseases. Furthermore, with a decrease in precipitation, an increase in evapotranspiration, and a shorter snow cover season, the top layer of soil may dry out. This can stress aspens and lead to forest cover loss. Lower pond levels will affect rivers, also harming downstream ecosystems and migratory birds. In certain years, there may be an increase in precipitation, but it is often outside of the summer months, which is when these ponds and peatlands rely on water. Wetlands and peatlands can regulate water table levels in the near future but over time this will become increasingly difficult. Aspens could potentially migrate northwards but most likely not faster than climate change travels. This region will need to adapt to less water availability than in the past.
This study provides yet another blueprint for simulating climate change impact analyses using HydroGeoSphere. The use of a 2-dimensional model demonstrates the ability to model water availability over a range of sensitive ecosystems over an extended period of time, while minimizing the overall computational requirements typically associated with larger, watershed-scale studies.
“The [HydroGeoSphere] numerical formulation allows the user to specify boundary conditions in the form of atmospheric fluxes, rather than specifying net groundwater recharge rates and surface water levels that necessitate additional a priori assumptions.”
Abstract:
Ecosystems within the subhumid Boreal Plains of Northern Alberta host ecologically and commercially significant habitat and natural resources. However, these ecosystems exist under a delicate hydrologic balance that may be upset as the climate warms by 2 to 5 °C over the next century. In this study, numerical simulations were used to predict climate change impacts at a catchment composed of a mosaic of Boreal Plains ecosystems including a small pond, peatlands with sparse black spruce, and hillslopes with predominantly aspen forests. Simulations were conducted with a fully integrated groundwater–surface water code using a 2‐D model previously calibrated to a decade of hydrologic data that included a range in climatic conditions. Projections from 13 climate change scenarios were simulated from 2011 to 2090 and compared to a base case scenario that assumed no climate change. Results indicate peatland water levels may decline by up to 1 m; however, sensitivity simulations indicate that the decline in water levels may be moderated by several feedback mechanisms that restrict evaporative losses and moderate water level changes. In contrast, higher evapotranspiration losses from the aspen hillslopes are predicted to result in near‐surface soils becoming increasingly drier. Thus, the aspen may frequently be water stressed and increasingly susceptible to secondary maladies such as pests and disease. Reduced pond water levels are also predicted with the development of frequent ephemeral conditions in warmer and drier scenarios. Concurrent decreases in stream flow may further impact downstream ecosystems. Further research into the regional health and sustainability of Boreal Plains ecosystems is warranted and could benefit from the development of improved numerical tools capable of extending the processes considered.