Climate change trends on the Prairies

Research found increases in growing degree days, corn heat units, the number of frost-free  days, and average, maximum and minimum air temperature on the Prairies. Average annual precipitation and growing season precipitation have increased in Canada, but western Canada had increases in some regions and decreases in others. Annual snowfall, snow cover duration and off-season precipitation have decreased in Canada since 1950. Over time, wheat, barley and canola yields have increased, primarily due to better genetics.

A literature review was conducted to assess climate change trends from across Canada with a focus on the Prairie provinces from 1900 to 2021. The review included refereed journal articles, books, government documents, and creditable website documents.

Between 1948 and 2012, Canada’s average annual air temperature rose by 1.7 C (range 1.1–2.3 C), compared to global average air temperature increase of 0.8 C between 1900 and 2020. Since the 1970s, a steady increase has been observed in Canada, with northern British Columbia and Alberta increasing the most with average air temperatures in the winter increasing by 4 to 6 C between 1948 and 2012.  Other research found that from 1920 to 2019, Canada’s average air temperature had increased by 0.9 C, with a range from 2.1 to 3.0 C.

In eastern British Columbia, Alberta, Saskatchewan, and western Manitoba, the average annual air temperature saw significant increases in all seasons. Increases ranged from 2 to 4 C during the winter.

Daily maximum and minimum temperatures also show warming trends. Over the 1948 to 2016 time frame, daily maximum temperatures across Canada in the summer had increased by 0.9 C, and daily minimum temperatures had increased by 1.3 C. Winter temperatures increased more, with the daily maximum temperature increasing by 1.4 C and daily minimum temperatures by 2.1 C.

On the Prairies, warming has occurred since 1951 and the annual average daily maximum temperature has increased by 0.2 C per decade from 1951 to 2004 for a total increase of 1.2 C. Average minimum temperatures during the same time period increased by 0.3 C per decade totaling a 1.4 C increase. Overall, both maximum and minimum air temperatures have risen in the Prairies and proportionately more in winter and spring than in summer and fall.

The number of growing degree days (GDD) increased by an average 178 GDD across Canada from 1948 to 2016. The frost-free period in across Canada has also increased by 22.4 days over the 1895 to 2007 period. These have led to a longer growing season, increasing by 3 to 12 days in the Prairies region from 1920 to 2020, along with the potential for new crops like corn.

From 1948 to 2012, Canada’s average total annual precipitation increased by 19%, ranging from 15% to 22%. However, changes in annual precipitation were variable across the country, with decreases in southwest British Columbia, Alberta, and Saskatchewan.

Growing season precipitation trends on the Prairies saw an increase in rainfall during 1956 to 1995 of 0.98 mm per year in the May to August time frame.

Snow water equivalent (SWE) has decreased in western Canada with an average maximum SWE decrease of approximately 2–10 mm per decade at high elevations over the 1950–2010 period.

Yields have increased

From 1904 to the 1930s, wheat yields generally decreased with large drops in the 1920s and mid-1930s due to drought and disease. In the late 1930s and into the  mid-1940s, better growing conditions and the release of the new stem rust-resistant variety Thatcher resulted in an increasing yield trend. From 1958 to 1978 wheat yields increased rapidly across the Prairies.

In southern Alberta, central/ southern/eastern Saskatchewan and southern Manitoba, an increase in maximum wheat yield potential of 5.3 to 8 lbs/ac/year (6 to 9 kg/ha/year) was observed over the 1947 to 1992 period.

From 1972 to 1990, CWRS yield gains were 0.35% per year across western Canada, but rose to 0.67% for the 1993 to 2012 time period.

From 1971–1980 to 1991–1996 barley yields increased by over 25% across the Prairies.

Canola yields have steadily risen in the 1960s and 1970s when cultivars were still rapeseed, Yields in this time period were 18 bu/ac (1.01 tonnes/ha) and rose to 23 bu/ac (1.29 tonnes/ha) in the late 1970s and 1980s. More recently from 2000 to 2013, canola yields increased by 48 lbs/ac/year (54 kg/ha/year), primarily because of the introduction of herbicide tolerant/hybrid varieties.

Overall, studies focusing on the Prairie Provinces in Canada have shown accelerated changes in several climate parameters over time, affecting cropping areas and crop yields. But uncertainty exists on the relationship between crop yield and long-term climate changes.

Funding for the project was provided through a grant from Natural Sciences and Engineering Research Council.

Emmanuel Mapfumo, David S. Chanasyk, Dick Puurveen, Shannon Elton, and Sachin Acharya. 2023. Historic climate change trends and impacts on crop yields in key agricultural areas of the prairie provinces in Canada: a literature review. Canadian Journal of Plant Science. 103(3): 243-258.

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