Forests are a defining landscape feature for much of the Midwest, from boreal forests surrounding the northern Great Lakes to oak-hickory (Quercus spp., Carya spp.) forests blanketing the Ozark Highlands. Savannas and open woodlands mark a major transition between forest and grassland biomes in the United States. Forests cover approximately 28 percent of the area in the eight-state Midwest region and help sustain human communities ecologically, economically, and culturally. Forest ecosystems are distributed according to patterns of climate, moisture, soils, and disturbance; ecoregions capture these broad patterns across the landscape. Most of the Midwest is contained within the Laurentian Mixed Forest, Eastern Broadleaf Forest (Continental and Oceanic), and Prairie Parklands ecoregions (Bailey 1995) (fig. A1-6). The broad diversity in species composition and structure across the Midwest will likely engender higher resilience to a changing climate than less diverse biogeographic regions, but each ecoregion might be best characterized by a few strong vulnerabilities. With this in mind, key vulnerabilities related to climate change are summarized below according to ecoregions. The term "vulnerability" refers to a decline in vigor and productivity, in addition to more severely altered community composition or ecosystem function (Swanston et al. 2011). In other words, a species or ecosystem may be considered vulnerable to climate change by virtue of significantly decreased well-being, even if is not projected to disappear completely from the landscape.