Freshwater Fisheries in Canada: Historical and Contemporary Perspectives on the Resources and Their Management

Chapter 16: Climate Change and Its Impact on Freshwater Fishes and Fisheries in Canada

Cindy Chu, Derrick T. de Kerckhove, Matthew M. Guzzo, and Mark S. Poesch


Greenhouse gas (GHG) emissions are the most significant driver of observed climate change since the mid-20th century, and the Intergovernmental Panel on Climate Change (IPCC) acknowledges that humans are the main cause of current global warming (IPCC 2013, 2021; Pachauri et al. 2014). Human activities that contribute to GHG emissions include sus¬tained increases in human populations; fossil fuel consumption for industry, manufacturing, electricity, and transportation; deforestation and land conversion; and agricultural intensification and ruminant livestock populations (Ritchie 2020; Ripple et al. 2020). Based on 2016 estimates, GHG emissions generated by human activities account for ~55.46% of the total global emissions, outstripping natural sources (e.g., forest fires, oceans, wetlands, permafrost, mud volcanoes, volcanoes, and earthquakes) and exerting extra pressure on what is otherwise a self-balancing Earth system (Xi-Liu and Qing-Xian 2018). Total global GHG emissions increased from 24.5 gigatons of CO2 equivalent (GtCO2 eq) in 1970 to 37.2 GtCO2 eq in 2002 (Olivier and Peters 2020; Figure 1). Since 2002, global emissions have accelerated leading to 48.0 GtCO2 eq in 2011, after which the rate of increase slowed but measured 52.4 GtCO2 eq in 2019.

Greenhouse gas emissions are increasing land and ocean temperatures and altering the global hydrological cycle. Since 1980, these temperatures have been consistently warmer than the 20th century average (1901–2000), with temperatures since 2015 averaging ~0.93°C more than the global average (Smith et al. 2008; NOAA 2021; Figure 2). Since 1940, the global hydrological cycle has been fluctuating between periods of intensification and deintensifica¬tion (increased or decreased amounts of evaporation, precipitation, humidity, and extreme events, respectively) in different regions of the world (Koutsoyiannis 2020). For example, in Arctic Canada, the hydrological cycle has been intensifying. Warmer air temperatures have increased the humidity, precipitation, river discharge, glacier equilibrium line altitude, and land ice wastage (Box et al. 2019), whereas, in the southern Prairies, lake evaporation has been decreasing with decreasing windspeeds despite relatively stable air temperatures (Burn and Hesch 2007). These changes in air temperature and the hydrological cycle impact the availability and distribution of freshwater and the quantity and quality of freshwater habitats around the world.