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Technical Thematic Report No. 16. - Soil erosion on cropland – introduction and trends for Canada

Results - Canada

Due to climate, there are only important areas of Cropland in 8 of the 15 terrestrial ecozones+ in Canada – the Pacific Maritime, Western Interior Basin, Montane Cordillera, Boreal Plains, Prairies, Boreal Shield, Mixedwood Plains, and Atlantic Maritime (Figure 1). There are minor areas of Cropland in the Newfoundland Boreal, Taiga Plains, and Boreal Cordillera. For the latter two ecozones+, Cropland area is so limited that it is not feasible to make meaningful estimates or interpretations of erosion risk so they were excluded from this analysis. Only 6.7% of Canada’s land area is Cropland.Footnote[7] The Prairies is the only ecozone+ where Cropland is the dominant land use (54% of area). Cropland is also a major land use in the Mixedwood Plains (40%) and Boreal Plains (11%). In all other ecozones+, Cropland makes up less than 5% of the land area and it amounts to less than 0.5% of total zonal area for the Newfoundland Boreal, Boreal Shield, Montane Cordillera, and Pacific Maritime. Nevertheless, even where Cropland is a minor land use it is usually located adjacent to important population centres and transportation corridors so its potential environmental impact on human population is far greater than its relatively small proportion of total land area. Cropland will often locally occupy the majority of land in particular landscapes, such as well drained relatively level soils in valleys, and be completely absent in other landscapes, such as steep slopes. Therefore, Cropland management will have large local impact on soil erosion in a few particular landscapes within the ecozone+ while having little or no influence on the state of many other landscapes within the ecozone+. The relationship between erosion and biodiversity is complex and not well studied. The degradation and instability caused from erosion is usually considered detrimental to biodiversity.

Figure 1. Cropland in Canada by soil erosion risk class, 2006.

map

Long Description for Figure 1

This map of Canada shows cropland in Canada by soil erosion risk class in 2006. Eight of fifteen ecozones+ contain areas of Cropland: the Pacific Maritime, Western Interior Basin, Montane Cordillera, Boreal Plains, Prairies, Boreal Shield, Mixedwood Plains, and Atlantic Maritime. The majority of Cropland in Canada is in the very low soil erosion risk class, with scattered areas of low risk throughout, and a few small areas in the moderate class in the southern regions of western Canada. The Great Lakes region of the Mixedwood Plains is a mix of low to very high classes. The Atlantic Maritime is predominantly a mix of very low to moderate classes, with a patch of very high soil erosion risk on the east coast of Nova Scotia in addition to patches of very high risk in Newfoundland Boreal ecozone+.

 

All SLC polygons containing >5% Cropland were included in the analysis and are shown here.

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Soil erosion continues to be a threat to agricultural sustainability in Canada. Nevertheless, on average, soil loss from the combined effects of wind, water, and tillage decreased in all ecozones+ between 1981 and 2006 (Figure 2). Over that period the proportion of Cropland in the very low risk class (sustainable) increased from 64 to 80%. The increase in land with very low risk was due to reduction in tillage intensity and conversion of some erodible landscapes from annual crops to perennial forage and tame pasture. The Boreal Plains and Prairies ecozones+ contain 18 and 67%, respectively, of total Cropland in Canada so the important reductions in wind and tillage erosion risk in these regions dominate the national erosion risk situation. In those regions the practice of summerfallow (leaving the land bare for one entire growing season) has also decreased markedly in the last 25 years and this has effectively reduced erosion risk. In 2006, 10% of Cropland remained in the moderate to very high risk classes, reflecting high levels of water erosion in the Mixedwood Plains and Atlantic Maritime ecozones+.

Figure 2. Soil erosion risk for Cropland in Canada, 1981-2006.

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Long Description for Figure 2

This bar graph presents the following information:

Percentage of agricultural land
YearVery low
(<6 t/ha/yr)
Low
(6-11 t/ha/yr)
Moderate
(11-22 t/ha/yr)
High      
(22-33 t/ha/yr)
Very high
(>33 t/ha/yr)
198165.416.312.02.44.0
198665.916.411.72.33.6
199168.015.411.22.13.3
199671.814.09.41.92.8
200176.311.67.71.92.6
200681.88.85.61.52.3

Soil erosion risk for Cropland in Canada, 1981-2006.

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Footnotes

Footnote 7

Cropland, as discussed throughout this report, also includes areas defined as Improved Pasture and Summerfallow in the Census of Agriculture, and thus the statistics reported here may differ from other thematic reports. See the Agri-environmental indicators section on page 1 for more information.

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