1. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Trends in Summer Fallow and Climate Variables in the Canadian Prairies S. Gameda, B. Qian, C. A. Campbell, R. Desjardins WMO Expert Meeting Contribution of Agriculture to the State of Climate September 27-30, 2004

2. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Land Use Change in the Canadian Prairies Beginning in the 1870s over 55 Mha of land brought into agricultural production Of this, 30-32Mha under annual crops Summer fallow introduced in the early 1900s for moisture conservation –Expanded to a peak of 16Mha (late 1960s) –Currently ~ 5.5-6.0Mha What impact has this had on regional climate? Is it possible to differentiate the agricultural “signal” from climate variability and change?

3. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada

4. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Some Characteristics of the Canadian Prairies Soil Zone Mean Annual Temp. (C) Annual Precip. (mm) ET (mm) Deficit (mm) Brown5<350700400 Dark Brown2-5350-425650250-275 Black0-2>400500-6000-150

5. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Area Under Summer Fallow Soil Zone Crop Land ( M ha ) Area Under Summer Fallow (Millions of hectares) 197519801985199019952000 Brown6.53.1 2.92.82.92.5 Dark Brown 8.53.63.42.72.62.11.6 Black15.04.74.22.6 2.01.3 Total30.011.410.78.28.07.05.4

6. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada

7. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Some trends in summer and winter temperature and precipitation for the different soil zones

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23. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Summary of Trends In Climatic Variables Summer (JJA)Winter (DJF) Brown No trends in Tmax, Slight increase in Tmin Increase in Tmax, Tmin Marginal increase in Precip.No trends in Precip. Dark Brown No trends in Tmax, Tmin.Increase in Tmax, Tmin No trends in Precip.Marginal decrease in Precip. Black No trends in Tmax, TminIncrease in Tmax, Tmin Increase in Precip.Decrease in Precip.

24. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Land Use Trend Considerations Significant shifts in use of fallow on the Canadian Prairies –Increase from advent of agriculture to ~1965-70 (max ~ 16M ha) –Decrease to 5.5 -6.0 M ha Similar large scale shifts in Northern US Impacts of type of fallow –Tillage (bare soil) –Chemical (light cover) Implications wrt regional climate –Summer/winter temperatures, precipitation

25. Agriculture and Agriculture et Agri-Food Canada Agroalimentaire Canada Land Use – Climate Interactions What impact does the use of summer fallow on such a large scale have on regional climate? How can this be differentiated from climate variability and climate change?