Madison, Wisconsin, USA Photograph by Michele Thieme   Central North America: Central United States Temperate Broadleaf and Mixed Forests   64,100 square miles (166,100 square kilometers) -- about the size of Washington Critical/Endangered

· Where the Grasses Meet the Trees
· Special Features
· Did You Know?
· Wild Side
· Cause for Concern
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Where the Grasses Meet the Trees

In this "in-between" ecoregion, aptly named the Upper Midwest Forest/Savanna Transition Zone, a unique blend of habitats separates the grasslands to its west and the forests to its east. This transition of habitats includes a mix of forests, savannas, and open woodlands. Today, the oak-savanna of this ecoregion is one of the world's most endangered ecosystems.

Special Features

Characterized by a mosaic of forests, savannas, and woodlands, the Upper Midwest Forest/Savanna Transition Zone is one of three transition ecoregions that helps separate the grasslands of the Great Plains from the forests of the eastern United States. Fire and drought have historically played key roles in shaping the boundaries of this ecoregion, which may have covered a much larger area during periods when there were extensive fires. The last concentration of tallgrass prairie savanna in the United States can be found here. It is an important migratory site for geese and is home to populations of river otters that extend out to the prairies.

	Brown-headed cowbirds, a brood parasite, live here. Brood parasites lay their eggs in the nests of other species of birds, and their young are raised by the unaware foster parents!

Wild Side

This ecoregion is dominated by species of oak, maple, and basswood and is unique in that it contains the last concentration of tallgrass prairie savanna in the United States. Many of the same animal species that once lived in the original savanna of this ecosystem can still be found here, because they have adapted to living in a mosaic of grassland and forests.

Cause for Concern

By the early to mid-19th century, most of the savannas of the Midwest were completely fragmented and nearly entirely destroyed by clearing, plowing, or overgrazing. And what remained in semi-natural habitats suffered invasion by woody shrubs--a consequence of fire suppression. Today, less than five percent of the original ecoregion is intact, and the oak-savanna component is one of the most endangered ecosystems in the world. Recent estimates of remaining savanna fragments testify to the critical status of this ecoregion: Only 0.8 square miles (2 square kilometers) of intact examples of oak-savanna vegetation remain in Wisconsin, or less than 0.01 percent of the original 11,196 square miles (29,000 square kilometers). At least 11 species of herbaceous plants, as well as several species of invertebrates, are threatened. Some of the threats that conservationists are addressing include the desire for homes built in more "natural" areas, lack of general awareness of the globally threatened status of oak-savanna vegetation, fire suppression and misunderstanding about the importance of burning in maintaining the integrity of the ecosystem, and invasion by exotic plants such as honeysuckle and reed canary grass. Grazing of wooded sites by cattle and deer also continues to be a problem.

For more information on this ecoregion, go to the World Wildlife Fund Scientific Report.