Michigan's Vegetation circa 1800
Between 1816 and 1856, the lands of Michigan were surveyed by the General Land Office, which had been established by the federal government in 1785. These surveys established the political boundaries of our current counties and townships throughout the state. The detailed notes taken by the land surveyors have proven to be useful in describing Michigan's natural landscape as it appeared prior to intensive lumbering and later agricultural or urban development. Surveyors took detailed notes on the prairies, savannas, forests, wetlands, and lakes as each section line was measured out. They noted the locations of large natural disturbances, such as recent wildfires, large tree blow-downs, and beaver floodings. They also noted trails and settlements of Native Americans or early European settlers as they were encountered.
Ecologists from the Michigan Natural Features Inventory developed a methodology to translate the notes of the General Land Office surveys into an electronic map that can be used by researchers, land managers, and the general public. Approximately 80 different land cover types were recognized from the surveyor's records using existing knowledge of the Michigan's native vegetation.
This historical information will enable a more accurate assessment of changes that have taken place in Michigan's natural environment over the past two centuries. It can also aid in understanding much about the natural diversity and dynamic processes that existed in Michigan ecosystems immediately prior to the logging era. Because the map is in an electronic format, it can be processed with a computerized Geographic Information System (GIS). The GIS allows many complex analyses. For example, resource managers can now compare acreages of different vegetation types that exist today with what existed around 1800. We now know that roughly 50% of Michigan's upland forests have been converted for agriculture and urban development since 1800. Between 28-35% of historical wetland acreage has been lost statewide. Losses have been greatest (>40%) in southern Lower Michigan, intermediate (>25%) in northern Lower Michigan, and least severe (<20%) in the Upper Peninsula. Well over 50% of our cedar, black spruce, and tamarack swamps have been either drained or converted to other wetland types.
For any given county or township, planners can have a clearer idea of the changes that have occurred within their jurisdiction and develop priorities for conservation and habitat restoration. Surveyors' information on the composition of major forest types can aid in protecting and restoring biological diversity in Michigan's forest lands. Statewide inventories and assessments of individual forest or wetland types are made much more efficient and accurate by using historical maps to guide field work.
The presettlement vegetation maps for any given portion of the state can be purchased by the public and are distributed through the Michigan Resource Information System. The Michigan Natural Features Inventory is working to create wall-size maps of the state for public distribution.
Patrick Comer, Associate Ecologist
Michigan Natural Features Inventory