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

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

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.

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).

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.

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

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.