Model projections and other evidence support modest productivity increases for forests across northern Michigan under climate change, although there is uncertainty about the effects of carbon dioxide fertilization. Warmer temperatures are expected to speed nutrient cycling and increase photosynthetic rates for most tree species in the assessment area. Longer growing seasons could also result in greater growth and productivity of trees and other vegetation, but only if sufficient water and nutrients are available. It is expected that productivity will be reduced in localized areas, through disturbances such as fires, wind events, droughts, and pest outbreaks. In addition, lags in migration of species to newly suitable habitat may also reduce productivity until a new equilibrium is reached.