The paired aerial photos for each

The objective of the study was to investigate and quantify the contribution that agricultural land makes to the national carbon balance. The cropland area of Canada was first stratified into regions with distinctive climatic, soil, landform and agricultural production conditions, and historical aerial photographs were then used to identify typical woody cover types and their areal changes at random sample plots within each zone. Woody biomass associated with forests was not considered because such estimates fall under the domain of CFS, but observed changes relating to forest conversions are included in discussions on land cover change.