Land cover and climate for part of southern Manitoba : a reconstruction from Dominion Land Survey maps and historical records of the 1870s
Loading...
Date
2006
Authors
Hanuta, Irene
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
This thesis demonstrates the application of historical cartographic and written sources to reconstruct land cover and climate conditions of the recent past for part of southern Manitoba at a time just before the onset of intensive human land development for agriculture. Original Government of Canada Department of Interior Dominion Land Survey (DLS) township maps and survey field notebooks from 1871 to 1877 are analyzed to reconstruct land cover. Historic land cover information is compiled in a Geographic Infomation System (GIS), quantified and mapped, Details on the historic distribution and extent of prairie grasslands, wetlands, forested areas and water bodies are captured in the GIS. The DLS graphic and written historical records yield land cover information with a fine spatial and temporal resolution for the study area. The main study area comprises 170 townships covering about 16,500 km2 and 10 parishes. Township and parish maps show land cover information for known locations that are attached to specific dates. Tree ring data, instrumental measurements and newspaper accounts provide climate and other environmental information. Climate conditions just before and during the surveys are analyzed to identify relationships between land cover characteristics and temperature or precipitation patterns. Annual and seasonal land cover and climate variability are apparent even over the short period of the study. Precipitation variability and extreme events (severe storms or drought) produced most impacts on land cover appearance, including influencing wetland distribution and extent, and the occurrence of grass and forest fires. Comparisons are made between the 19th century reconstructed pre-settlement land cover and 20th century land cover information from the Prairie Farm Rehabilitation Administration satellite-classified imagery. The comparisons clearly show the extent of environmental change of the recent past after maps are generated and data quantifying land cover areas presented. Being in digital format, the 19th century land cover information is used to generate a series of example maps for viewing and analysis at a variety of spatial scales and for analysis of specific features, such as wetlands. The digital format also allows these data to be available for other applications. With settlement of the Canadian Prairies, dramatic, human-initiated changes to the landscape occurred with forest clearing and wetland drainage to accommodate agriculture. In the study area, in the 19th century, about 55% of the land cover is classified as grasslands; wetland areas comprise at least 10%; and wooded areas about 35% of the landscape. In the 20th, nearly all of the original grasslands have disappeared; wetland areas make up less than l% of the area; and about 9% of the land is treed. But even before large numbers of immigrants arrived in southern Manitoba, the prairie landscape underwent dynamic and continuous changes caused by climate variability and change, and by impacts of large herds of grazing animals or fire. However, the human influences, especially the last two centuries, have contributed to rapid changes of land cover over a short period. These human-caused land cover changes are playing a role in influencing present-day and future regional climate patterns.