The SRB poses globally-important science challenges due to the importance and diversity in its cold region hydro-climate and ecological zones, the rapid rate of environmental change and the need for improved understanding, diagnosis and modelling of environmental change. Key biomes are of regional and global importance and include the Rocky Mountains, Boreal Forest and the Prairies.
Within the SRB, the sensitivities to climate change are most noticeable in the west, where changing temperatures are producing smaller snow packs and earlier melt, decreasing glacier size and shifts in the river’s runoff regimes. Glacier coverage has declined by ~25% in the last quarter century and the spring snow-covered period has shortened by approximately one month. Associated with these declines is a shift from snow to rain on the eastern slopes and a decrease in streamflow across both glaciated and non-glaciated streams in the headwaters of the Saskatchewan River.
The Western Boreal Forest and Prairies have experienced large swings in climate that have resulted in severe weather, with some of the driest and wettest period in the last 140 years occurring since the turn of the 21st century. This has resulted in extensive areas experiencing large soil moisture deficits, drought-induced dieback of major tree species, wetland and stream disappearance, and recorded minimum groundwater levels during the drought of 1999-2004, with multi-billion dollar economic losses to agriculture. In contrast, the recent wet periods of 2010 and 2011 produced extensive (>1 in 500 year) flooding in the prairies, inundation of wetland vegetation and record groundwater levels.
Such large swings in climate are occurring at a time of unprecedented resource extraction and agricultural activity, both of which are intricately linked to hydroclimatic conditions. Because of the interactions between hydrology and vegetation, the southern boreal forests of western Canada are expected to be an area of maximum ecological sensitivity to stressors in the 21st century. Throughout the Prairie Provinces, population growth and the continued demand for more food and biofuels is leading to increased nutrient loadings in runoff, affecting amenity and ecosystem health, and potentially threatening water supplies. Farming practices such as drainage and wetland removal are changing the ecological services that the landscape is able to provide.
The implications of these complex and interconnected changes to the land surface and the resulting feedbacks with the atmosphere remain poorly understood, and the rate of change is so high that there are important concerns that current Earth system models, developed on historical data and an assumption of climate stationarity, have limited predictive capability. Current models have not considered the full range of feedbacks between the atmosphere, hydrosphere, cryosphere and terrestrial ecosystems that occur from small to large scales and are anticipated to be particularly intense in this region. This shortcoming already degrades model predictability and resource management; for instance, North America Regional Climate Change Assessment Program (NARCCAP) simulations of current climate show up to 60C positive air temperature bias over this region and recent years have seen failure of water and land management systems with high economic, environmental and social consequences.
Improved understanding and prediction are urgently needed to provide better planning and management for water supply, transportation, disaster management, energy, food security and ecosystem sustainability. Increasing pressures on the water environment are also leading to the need for new social science research, for example to understand stakeholder concerns for water security, to provide insight into governance structures and policy instruments, and to understand societal resilience to extreme events.