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Univ. of Alberta Climate Change Impacts on Canadian Agriculture R.F. Grant Dept. of Renewable Resources, Univ. of Alberta, Edmonton,Alberta.

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Presentation on theme: "Univ. of Alberta Climate Change Impacts on Canadian Agriculture R.F. Grant Dept. of Renewable Resources, Univ. of Alberta, Edmonton,Alberta."— Presentation transcript:

1 Univ. of Alberta Climate Change Impacts on Canadian Agriculture R.F. Grant Dept. of Renewable Resources, Univ. of Alberta, Edmonton,Alberta

2 Univ. of Alberta Climate Change Impacts - Positive n Higher concentrations of atmospheric CO 2 (C a ) raise CO 2 fixation rates and hence plant productivity -Doubled C a raises plant growth by ~30% (C 3 ) and ~10% (C 4 ) -This rise is smaller if nutrients are limiting n Higher C a lowers transpiration rates and hence water requirements -Doubled C a lowers water requirements by ~ % -This reduction is larger if nutrients are limiting n Higher temperatures raise CO 2 fixation rates, lengthen growing season -Plant productivity increases with mean annual temperature to 15 o C n Higher temperatures accelerate mineralization, nutrient uptake

3 Univ. of Alberta Climate Change Impacts - Negative n Higher temperatures raise evaporation rates and hence water requirements -3.5 o C increase raises water requirements by ~25%. -Offsets reduction in water requirements from higher C a -more rapid soil drying during mid-continental summers can cause greater risk of agricultural drought, forest fires, and decreased quality and quantity of water in reservoirs. n However higher temperatures are also expected to cause higher precipitation (3.5 o C rise in temperature  8-10% rise in precip.) -Precipitation may become more variable, which reduces productivity, increases erosion. -Effects of variable rainfall on productivity can be reduced by soil and water conservation practices that maintain SOM and improve WUE.

4 Univ. of Alberta Climate Change Impacts - Negative n Higher temperatures raise respiration rates and hence C loss to atmosphere -Offsets C gain at mean annual temperatures greater than 15 o C n More frequent heat waves over most land areas can cause heat stress in livestock and crops n Higher minimum temperatures allow expanded ranges for pests and diseases of humans, livestock and crops (e.g. grasshoppers, potato beetle).

5 Univ. of Alberta Climate Change Impacts on Agricultural Geography during the 21 st Century – Key points n Frost free season will be extended by ~40 days. -Growing seasons are already lengthening by 1 to 3 days per decade in northern regions -May need longer-maturing, heat-tolerant crop varieties n Seeding dates of annual crops will be ~3 weeks earlier n Regrowth of perennial crops will start 2-3 weels earlier and critical fall harvest dates will be 2-3 weeks later n Spring wheat will be replaced by winter wheat through most of the prairies n Corn may replace other cereals and soybean may replace canola through the southern and central prairies n Ponderosa pine may replace lodgepole pine in foothills forests.

6 Univ. of Alberta Climate Change Impacts on Agricultural Productivity during the 21 st Century – Key points n Average yields of canola and cereals in western Canada will increase from current levels by 10% to 30% by the end of the century n This increase will be larger in central and cooler regions (e.g. Peace River) and less in warmer regions (e.g. southern Saskatchewan) n The size of this increase depends upon the amounts by which temperature and precipitation rise -e.g. in southern Saskatchewan if temperature rises by 3 o C and precipitation does not rise, then average yields will rise only marginally, but their variability will increase – insurance, storage. -But if temperature rises by 6 o C and precipitation does not rise (worst case scenario), then average yields will decline and crop failure will become more frequent n Grassland productivity will increase by 20% to 25% -Changes in species composition (e.g. C 3 to C 4 ) may be an issue

7 Univ. of Alberta Climate Change and Land Use in the 21 st Century n Much of the increased agricultural productivity from climate change in N. America will be realized by northward expansion of cultivation -Possibly as much as 60Mha, depending on emission scenario -But northern soils are largely luvisolic, with fertility limitations to agriculture n This expansion will be offset by loss of cultivable area in most regions of Africa and in NE Brazil and Australia.


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