Past, Present, and Possible Future Trends with Climate Change in Illinois Forests

There have been dramatic changes to forest lands since the end of the last ice age, about 14,000 years before present, when boreal ecosystems were eventually replaced by deciduous forest and grassland. In Illinois at the time of Euro-American Settlement (circa 1820), forest lands, including fire- maintained woodlands and savannas, comprised about 42% of the land area. Habitat destruction, fire absence, livestock grazing, and infestations of non-native species have altered forests since the 1800s. Currently, forest land cover statewide is about 13.5%, mostly (83%) in private ownership and predomi- nately (68%) classified as oak-hickory cover type. Further modifications can be expected due to climate change, predicted for Illinois over the next 100 years to include warmer winter temperatures, warmer and wetter springs, and hotter, drier summers. Models predicting potential futures for 113 tree species as a response to climate change over the next 100 years were generated for ten primary Illinois ecoregions. Results indicate that there are likely to be increases in habitat suitability and capability for some species and decreased habitat suitability and capability for others with variability across ecoregions. Many species demonstrate differential re- sponses to changing climate from north to south in the state. The dominant species in the oak-hickory cover type generally are projected to have fair to good capabilities, with some notable exceptions; how- ever, Acer saccharum, a competitor in many oak-hickory stands, also is projected to have fair to good capability. Dominant species in mesic upland and bottomland forests include a rich variety of species about evenly split between those with fair-to-good capabilities and those expected to have poor capa- bility. Potential ‘New Habitat’ and ‘Migrate’ species also are identified. New Habitat species are those that have potential habitat appearing in the state within 100 years; Migrate species have some potential for natural distribution to the state within 100 years and could be considered as candidates for assisted migration northward. Considerations for conservation and management of forest lands are discusse