4.1 Ecoregion

Minnesota lies at a crossroads of ecological land types, with widespread differences in soils, underlying geology, and plant and animal communities. These differences are identified and classified into ecoregions, or broad areas in Minnesota that share similar land uses, soils, land and surface form (topography), and potential natural vegetation. Minnesota is classified into seven ecoregions. Ninety-eight percent of Minnesota 's lakes occur in just four of them: Northern Lakes and Forests, North Central Hardwood Forests , Western Corn Belt Plains, and Northern Glaciated Plains. The other three ecoregions, Northern Minnesota Wetlands, the Red River Valley, and the Driftless Area, contain few lakes, but are rich in streams.

4.1.1 Comparison

Lakes and rivers within ecoregions often have similar physical characteristics, water chemistry, and biological communities because they occur in an area of similar land type. It is often said that, "A lake is a reflection of its watershed," and therefore of its ecoregion. In other words, what happens on the land and the basic characteristics of the land (soil, geology, vegetation, drainage, etc.) affects the quality and health of a lake or stream. The number, appearance, and condition of lakes vary among ecoregions because of glacial history, geology, soil type, land use, and climate. Typical values for chemical and physical measurements have been compiled for the four lake-rich ecoregions by evaluating information from minimally impacted lakes and rivers. These values provide a "yardstick" for comparing other lakes and rivers in the same ecoregion.

4.1.2 Distinction

Northern lakes are often fairly small and relatively deep compared to the large, shallow lakes common in southern Minnesota. These differences can be understood by observing that these lakes occur in two different ecoregions. Soils in the Northern Lakes and Forests ecoregion tend to be lower in nutrients than soils in the Northern Corn Belt Plains ecoregion, causing the northern lakes to be less productive.

In addition, the size and depth of a lake influence characteristics such as water clarity and acidity. Lakes that are deep relative to their size, such as those in northern Minnesota , tend to be clearer with less nutrient-rich water. In contrast, lakes that are shallow relative to their size, such as those in southern Minnesota , tend to be more eutrophic (enriched with nutrients, resulting in more algae and greater plant growth). Common land use practices also differ as one moves from southern to northern Minnesota .

Ecoregion differences also influence a lake's sensitivity to human impacts. For example, watersheds in northern Minnesota are often rocky, with thin soils that have a minimal capacity to buffer acidic input from the atmosphere. Watersheds to the south have deeper soil, better able to buffer acidic inputs, but with more potential to cause impacts to lakes from sediments and turbidity.

4.1.3 Significance

Typical values for chemical and physical parameters have been compiled for the seven ecoregions by monitoring unimpacted water bodies (lakes or streams with minimal human disturbance). These values help us identify what conditions might have existed before human settlement and help us develop realistic expectations for how lakes or streams might be restored to a more "natural" state. It is unrealistic to expect a shallow, southern Minnesota lake to have the same water clarity or productivity, for example, as a northern Minnesota lake. Ecoregions help us understand these differences.

4.1.4 Setting

The Pelican group of lakes and the Pelican River watershed are located in the North Central Hardwoods ecoregion. This ecoregion is an area of transition between the forested areas to the north and east and the agricultural areas to the south and west. The terrain varies from rolling hills to smaller plains. Upland areas are forested by hardwoods and conifers. Plains include livestock pastures, hay fields and row crops such as potatoes, beans, peas and corn.

The ecoregion contains many lakes, and water clarity and nutrient levels are moderate. Land surrounding many of these lakes has been developed for housing and recreation, and the densely populated metropolitan area dominates the eastern portion of this region. Water quality problems that face many of the water bodies in this area are associated with contaminated runoff from paved surfaces and lawns.

Next page: Chapter 4.2 Basins and Watersheds