Introduction to Climate Change Adaptation and Mitigation Management Options

Climate is a critical factor shaping the structure and function of forest ecosystems in the Southern United States. Human induced changes in climate systems have resulted in an increase in the global average air temperature of about 0.8°C since the 1900s (Pachuri and Reisinger 2007). Data from long-term weather stations show that overall, the continental United States has warmed during the past century, but that the magnitude and direction of change vary by geographic area (Backlund et al. 2008). The primary driving force behind this overall warming is an increase in carbon dioxide (CO2) and other greenhouse gas emissions, a trend that is likely to continue over the next century (Karl et al. 2009). For example, by 2100, further warming in the United States is expected to range from 2.5°C to 5.3°C relative to the 1971 to 2000 time period (Kunkel et al. 2011). While warming and elevated CO2 are important aspects of climate change, projections of increased climate variability and extreme weather events—such as drought, heat waves, heavy rains, tornados, and hurricanes (Easterling et al. 2000; Huntington 2006)—are expected to have an even greater impact on forest ecosystems than increases in CO2 and temperature alone (Dale et al. 2001; Kunkel et al. 2011; Vose et al. 2012). Indirect effects may be equally or more significant, as the frequency, magnitude, and severity of wildfires, insect and pathogen outbreaks, and the spread of nonnative invasive species may be amplified by climate change (Vose et al. 2012). Combined, these direct and indirect effects of climate change are likely to create conditions that have not as yet been observed and may shape ecosystems in ways that have no historical analog (Williams and Jackson 2007). Some of these effects may be already occurring (Parmesan and Yohe 2003). For example, forest dieback, large insect outbreaks, and large wildfires during the past decade (Bentz et al. 2009; 2010; Breshears et al. 2005, 2009; Turetsky et al. 2010) may be signals of the potential effects of a rapidly changing climate on forest ecosystems (Vose et al. 2012). 1