Regional- and watershed-scale analysis of red spruce habitat in the southeastern United States: implications for future restoration efforts

Red spruce (Picea rubens) is an evergreen tree with a range from Canada to North Carolina that provides habitat for multiple rare, endemic species. Red spruce-dominated forests once covered over 600,000 ha in the southeastern US, yet currently occupy a small fraction of their historical range due largely to logging that began in the nineteenth century. To combat this loss, restoration groups have emerged to actively improve the health and areal extent of red spruce. This study was conducted to (1) predict how suitable habitat for red spruce in the southeastern US is expected to change by the year 2100 in response to increasing global temperatures and (2) illustrate how these predictions can be used, in concert with local-scale information, to support efforts to restore red spruce in this region. Red spruce currently occupies a small fraction of the area indicated by our model to be suitable. The area of habitat supportive of red spruce was projected to decline from present day to the year 2100, but the magnitude of this decline depended on the level of carbon emissions, and there was considerable variability between climate models. In our case-study watershed, suitability for red spruce is predicted to decline by 2100, but may still support red spruce under optimistic to moderate emissions scenarios. At this scale, restoration strategies should also take into account locally varying conditions such as the current distribution of red spruce and competitive shrubs that may inhibit growth.