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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
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Higher concentrations of atmospheric CO2 (Ca) raise
CO2 fixation rates and hence plant productivity
- Doubled Ca raises plant growth by ~30% (C3) and ~10% (C4)
- This rise is smaller if nutrients are limiting
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Higher Ca lowers transpiration rates and hence water
requirements
- Doubled Ca lowers water requirements by ~15 - 25%
- This reduction is larger if nutrients are limiting
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Higher temperatures raise CO2 fixation rates,
lengthen growing season
- Plant productivity increases with mean annual temperature
to 15oC
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Higher temperatures accelerate mineralization,
nutrient uptake
Univ. of Alberta
Climate Change Impacts - Negative

Higher temperatures raise evaporation rates and hence water
requirements
- 3.5oC increase raises water requirements by ~25%.
- Offsets reduction in water requirements from higher Ca
- 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.
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However higher temperatures are also expected to cause
higher precipitation (3.5oC 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

Higher temperatures raise respiration rates and
hence C loss to atmosphere
- Offsets C gain at mean annual temperatures greater than
15oC
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More frequent heat waves over most land areas can
cause heat stress in livestock and crops
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 21st Century – Key points

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
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Seeding dates of annual crops will be ~3 weeks earlier
Regrowth of perennial crops will start 2-3 weels earlier and
critical fall harvest dates will be 2-3 weeks later
Spring wheat will be replaced by winter wheat through most
of the prairies
Corn may replace other cereals and soybean may replace
canola through the southern and central prairies
Ponderosa pine may replace lodgepole pine in foothills
forests.
Univ. of Alberta
Climate Change Impacts on Agricultural
Productivity during the 21st Century – Key points
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Average yields of canola and cereals in western Canada will
increase from current levels by 10% to 30% by the end of the
century
This increase will be larger in central and cooler regions (e.g.
Peace River) and less in warmer regions (e.g. southern
Saskatchewan)
The size of this increase depends upon the amounts by which
temperature and precipitation rise
- e.g. in southern Saskatchewan if temperature rises by 3oC and
precipitation does not rise, then average yields will rise only marginally,
but their variability will increase – insurance, storage.
- But if temperature rises by 6oC and precipitation does not rise (worst
case scenario), then average yields will decline and crop failure will
become more frequent

Grassland productivity will increase by 20% to 25%
- Changes in species composition (e.g. C3 to C4) may be an issue
Univ. of Alberta
Climate Change and Land Use in the 21st
Century

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
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This expansion will be offset by loss of cultivable area in most
regions of Africa and in NE Brazil and Australia.
Univ. of Alberta