HNA Summary Report
Existing Conditions
Terrestrial Habitat Distribution

It is useful to examine the patterns of landscapes when assessing their ability to support desirable animal communities. An analysis of long-term change in several broad habitat classes helps assess general change over time. When examining existing conditions, or managing for discrete habitat or species, attention to fine details of habitat may be more appropriate.

Grassland
The review of historic ecological change presented earlier clearly demonstrates the loss of grassland land cover from Iowa to southern Illinois. The extent of grassland fragmentation and conversion are the most extreme changes in many parts of the UMRS. Grassland patch connectivity has been highly reduced, and connectivity to other natural habitats has been reduced where agriculture or development are adjacent to grassland patches.

Forest
Forest was and remains an important component of the floodplain landscape for many reptile, amphibian, bird, and mammal species. Contemporary forests are distributed differently and have different species composition than in the past. They are even aged and have low tree species diversity. Changes in response to river and floodplain development differ among geomorphic reaches. Floodplain forests in northern pooled reaches were replaced mostly by water impounded by dams and also by development. Forests remaining in the upper pooled reaches have species composition similar to the past. In the southern pooled reaches, the lower Illinois River, and the Open River south to the Kaskaskia River, open forests and grassland-oak savannas joining dense riparian forests and grasslands were eliminated, but riparian forests remain largely intact. In the Open River south of the Kaskaskia River, the floodplain was once almost completely forested, but was later cleared and levees were constructed to protect crops.

Marsh
Marsh fragmentation is difficult to assess because river marshes were not well mapped in early periods and they are inherently fragmented along backwater margins, wet meadows, and river banks. Generally, contemporary marsh communities are more abundant in northern river reaches than in southern reaches, where there are few backwaters, river water is turbid, and sediment quality is poor. Marsh patches are so small and widely separated in southern river reaches that they can barely even be seen at this map scale. There is greater absolute acreage of marsh habitat in northern pooled reaches, and the proportion of total floodplain area is very much greater, because the northern reaches have less total area than southern reaches (Fig. 14). In other words, marsh habitats are more abundant, widely distributed, and common in northern river reaches.

Agriculture
Croplands currently occupy about one-half of the total UMRS floodplain area, and agriculture is the dominant land cover class. Cropland distribution is skewed toward southern river reaches where levees protect the wide fertile floodplains. Agriculture is the largest continuous land cover class in the lower 500 miles of the Upper Mississippi River and the lower 200 miles of the Illinois River. Grasslands once occupied most of the current agricultural land, but forested areas were also converted to crops.