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People often associate Wisconsin with its forested landscapes. Almost half of Wisconsin’s total acreage is covered with trees, providing 16 million acres of forests for timber, recreation, wildlife habitat, and ecosystem services such as cleaning the air and water. Moreover, forests are like living history books, reflecting changes in both their physical and human environments. Records of such changes may help us plan for changes in the forest over the next century and beyond.

The forests of the Menominee Nation in northwestern Wisconsin are truly exceptional, harboring some of the only old-growth trees to survive the "Great Cutover" of Wisconsin’s forests in the mid- to late 19th century. These forests are also unique because they are located at the ecotone, or transition, between the region’s northern forest and southern prairie-savanna provinces, where species from both provinces occur. Dry-loving species like oaks and hickories tend to occur in southern Wisconsin, while species requiring more moisture and coolness, like the hemlock, yellow birch, and sugar maple, tend to dominate the northern part of the state.

Indeed, Wisconsin’s unique position at the junction of different climatic zones and at the border of the Great Lakes means that many species come together at the edge of their ranges, providing the state with significant species diversity. As climate warms, southerly trees may expand their ranges northward, just as they did following the retreat of glaciers from Wisconsin thousands of years ago. Today’s fragmented, heavily developed landscapes may limit this migration, however, so the post-glacial period is not a perfect analogy to help us understand the forest’s response to a changing climate. Species at the southern limit of their ranges may go locally extinct if they are pushed beyond their tolerance for hot and dry conditions. Researchers at the University of Wisconsin-Madison predict that under the climate conditions forecasted by our most rigorous models, species currently residing in Wisconsin’s Northwoods, like red pine, balsam fir, and paper birch, may fail to reproduce and go locally extinct.

On the other hand, a notable group of species may fare quite well as our climate changes: the invasive species, including plants, insects, and pathogens that threaten forest health. As climate change brings longer growing seasons, higher temperatures, and more extreme weather events, invasive species and diseases will have greater opportunities to spread. Invasive species are good at colonizing recently disturbed areas, and grow and reproduce quickly, giving them the upper hand over native species. There are over 20 introduced pathogens in U.S. forests, causing an estimated $2.1 billion in damage annually. A notable insect pest, the gypsy moth, infests 125 million acres of U.S. forests and costs $10.6 million each year in efforts to suppress it. Other pests of growing concern to Wisconsin foresters are the emerald ash borer, hemlock woolly adelgid, and beech bark disease. These pests and pathogens, in addition to the increased risk of fire posed by hotter and drier conditions, make managing forests an increasingly complex task. For the Menominee Nation, the uncertainties of climate change complicate their goal of thinking seven generations ahead to sustain forest health.

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