Coastal Services Center

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Change Summary: Descriptive Summary of the Major Land Cover Changes in the Coastal Great Lakes Region, 1995 – 2000

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The change summary below is organized into two parts, coastal Great Lakes and Michigan. Changes in Michigan are described separately because the data were developed as a separate mapping effort. The summary is an example of how changes can be observed at multiple spatial scales.

Coastal Great Lakes

In the coastal area of the Great Lakes, excluding Michigan, 3.7 percent of the land area, or 899,806 ha, changed land cover types from 1995 to 2000. The most significant change was an increase in urban area. Seventy-nine percent of the change to urban was at the expense of grassland, scrub/shrub, and cultivated areas. The cultivated category also expanded slightly (1.4 percent), suggesting that as urban development expanded into the surrounding agricultural landscape, other land covers were in turn displaced by cultivation in order to maintain the agricultural land base.

Overall, about 0.7 percent of the palustrine wetlands converted to other land cover types, representing an area of 29,266 ha. Only 17 percent of that area was due to new urban and converted cultivated land. Almost half of the wetland change was to other nondeveloped categories such as forest and grass. Possible explanations may include a decrease in water table levels or indirect loss of wetlands due to upstream development.

Finally, fully one-third of change from wetland was to water, representing over 23,827 ha. This finding was offset by a total of 15,799 ha of water that converted to wetland, for a net change of 8,029 hectares. This net change, to some extent, contradicts the possibility of a climatological explanation of the decrease in wetlands area. A closer look at the location of these changes may indicate cause.

Michigan

In Michigan's lower peninsula, 3.9 percent of the land area, or 366,262 ha, changed land cover types since 1995. Roughly three-quarters of this change occurred between cultivated and grassland areas as a result of crop rotation and periods of inactivity. The remainder of these changes were the result of urbanization on the fringes of developed areas and the natural succession of unmanaged fields to grass, scrub, or forest.

The vast majority of this urbanization occurred in southeast Michigan, around the fringes of the Detroit metropolitan area and Grand Rapids. Of the 26,439 ha of urban expansion in the lower peninsula, 68 percent occurred due to a loss in cultivated or grassland area, illustrating the growth of cities and towns into the surrounding farmlands.

In Michigan's upper peninsula, only 0.9 percent, or 41,178 ha, changed. Though this seems small compared to the change in the lower peninsula, the result is in large part due to the differing economies on the two peninsulas. The majority of land cover change, 17,645 ha, was forested land losses to grassland, much of which was due to silvicultural practices and preparation for urbanization.

Palustrine forest conversion to either palustrine scrub/shrub or palustrine emergent wetland accounted for 5,447 ha. The reasons for this are less clear. Harvesting of lowland forest species, such as cedar, and pulp species, such as aspen and balsam poplar, may be the primary causes. Other causes may include changing hydrologic regimes, among them beaver activity, causing the death of less flood-tolerant species.

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