Climate Change
Climate changes are already evident in Appalachia. Assessments conducted at greater regional levels in the Northeast and Southeast U.S. indicate increasing temperature trends over the past several decades (U.S. Global Climate Change Research Program, Karl et al. 2009) and suggest these will result in:
- longer growing seasons
- reduced number and duration of snow pack and ice-over events
- increasing frequency of days with extreme heat
- increasing water temperatures, and
- increased evapotranspiration by vegetation and in streams
Temperature changes will set into motion a cascade of environmental changes such as increased stream temperatures (which can reduce oxygen availability and other water quality parameters), increased stress on all species during extreme heat waves, and lower ability of native flora and fauna to compete or combat non-native invasive species and diseases.
Annual mean precipitation has also changed, generally increasing by approximately 0.14% per year. Changes in precipitation vary at the local level. Similar to observed mean temperature changes, changes observed for precipitation during summer months (June through August) were greater than the annual means (0.21% per year). These changes will result in changes to climate such as (Global Climate Change Research Program, Karl et al. 2009):
- increase in storms/heavy precipitation events
- earlier spring snowmelt resulting in higher peak flow periods
- changes to annual water budgets
- scouring effects of intense storms, which will increase erosion and sedimentation and alter the geomorphology of stream habitats including mussel beds
- periodic drought conditions or decreasing precipitation trends that could have extreme impacts on aquatic species dependent on specific instream flow regimes for feeding and survival, and
- reductions in instream flow will also further exacerbate sedimentation, nutrient, and chemical contaminants in the waterways
Significant changes in precipitation intensity, duration, and timing will have profound effects on all species within the Appalachian LCC, including humans. Impacts will include changes in species distribution, abundance, and assemblages, or difficult-to-anticipate combinations of these. In addition, changing conditions will likely increase population fragmentation and species extinctions. Competition for sometimes scarce water resources will increase the risk for adversity between urban, agriculture, industry, and natural resource interests. These factors will combine to influence the future condition of biotic communities of the Appalachians. Some examples documented in peer reviewed literature include:
- Climate will bring additional threats to systems already stressed by development, fragmentation, pollution, and invasive species (Rogers and McCarty 2000, Noss 2001, Willis et al. 2010). Changes in the frequency and severity of disturbances will contribute additional stresses (Dale et al. 2001, Seidl et al. 2011).
- Forest types and tree species distributions will generally migrate northward but fragmentation and other factors may prevent dispersal and lead to localized extirpations (Honnay et al.2002, Iverson and Prasad 2002, McKenney et al. 2007, Opdam and Washer 2003).
- Other terrestrial species distributions are changing, or will likely change, as a direct result of changing climate conditions or in response to changing vegetation (Currie 2001, Huntley 2008, McCarty 2001, Parmesan 2006, Parmesan and Yohe 2003, Thomas et al. 2004, Travis 2003).
- Annual phenological events measured over the latter portion of the 20th century appear to be trending earlier; a pattern observed across several taxa and geographic areas (Inouye at al.2000, Walther et al. 2002). Misaligned phenologies will increase species’ stressors and mortality.
- Climatic changes will alter hydrologic regimes (Meyer et al 1999, Rouse et al. 1997) and greatly impact aquatic species; particularly those found in the higher elevations of the Appalachians (Flebbe et al.2006).
