Future climate and fire interactions in the southeastern region of the United States

Fire has a profound, though paradoxical influence on landscapes of the southeastern U.S.; it simultaneously maintains native biodiversity and ecosystem processes but also threatens silvicultural resources and human landscapes. Furthermore, since the majority of the southern landscape is heavily influenced by human activities, contemporary fire regimes are human managed disturbances within extant fire-dependent ecosystems. Though there is considerable uncertainty in climate projections for the southeastern U.S., climate change will likely impact both prescribed fire and wildfire. In this review, we synthesize climate change-fire interactions, discuss the impacts of uncertainty in a human-dominated landscape, and illuminate how both climate change projections and their uncertainties might impact our ability to manage forests in the Southeast. We define the Southeast region as consisting of the Gulf Coastal Plain, Lower Atlantic Coastal Plain, Piedmont and southern Appalachians and associated subregions. This region has the greatest area burned by prescribed fire, the highest number of wildfires in the continental U.S. and contains globally significant hotspots of biodiversity, much of which is dependent on frequent fire. The use of prescribed fire as a management tool depends on a suite of weather and fuel conditions which are affected by climate. Over the next five decades, general circulation models (GCMs) consistently predict air temperature to increase by 1.5-3 °C in the Southeast. Precipitation forecasts are more uncertain with respect to the mean; but, most models predict an increase in precipitation variability. Increases in the likelihood of severe droughts may increase wildfire occurrence while simultaneously limiting the implementation of prescribed burning by restricting the number of days within current prescription guidelines. While the Southeast has among the highest potential for C storage and sequestration, a reduction in C sequestration capacity due to increasing disturbances such as drought, insect infestations, hurricanes and fire, is possible. The potential for long-term shifts in forest composition from climate-altered fire regimes if coupled with an increased potential for wildfire occurrence could reduce quality and quantity of water released from forests at times when demand for high quality water will intensify for human use. Furthermore, any reduction in prescribed burning is likely to result in decreased biological diversity, particularly in the Coastal Plain, a global hotspot of biodiversity. Lastly, more future area burned by wildfire rather than prescribed fire has the potential to negatively influence regional air quality. Mitigating the negative effects of climate change-fire interactions would require actively exploiting favorable seasonal and inter-annual climate windows. Monitoring the type conversions of agricultural and fiber production forest will be critical for long-term projections of fire risk and watershed impacts of altered fire regimes.