Mountain Climate - Mountain Geography: Physical and Human Dimensions - page 131

et al. 2010). These responses are largely but not entirely related to rising freezing levels
and reduced snowcover (Grace et al. 2002; Diaz et al. 2003). Many alpine plants and
tree seedlings not only respond to temperature changes, but are sensitive to day length
at the beginning of the growing period and increased CO 2 concentrations (Keller et al.
2005). A warming of seasonal mean temperatures of 3-5°C can reduce snowcover and
duration by more than a month on average (Keller et al. 2005). Some mountain forests
will experience changes to disturbance regimes, such as fire frequency and intensity,
blowdown (wind), drought, insects, and disease, caused by climate change and variab-
ility. The changing character of these systems with changing climates is poorly under-
stood, and few generalizations can be made for all mountain systems.
In response to the habitat changes, wildlife also migrates to find appropriate climatic
niches (Hansen et al. 2001; Nogués-Bravo et al. 2008; Mantyka-Pringle et al. 2012).
Because of microclimatic complexity, populations or single species could readily be in-
solated on individual slopes or peaks, as the mountain environment increases in frag-
mentation (Fig. 3.8; Beniston 2006). Since this climate shift is occurring rapidly, some
species may not be able to adapt or migrate quickly enough (Grabherr et al. 1994;
McCarty 2001). Not only must prey species adapt to new environmental conditions, but
behaviors will need to change as new predators migrate in or out of range (McCarty
2001). It is probable that some alpine and cold-water fish species will not survive cli-
matic changes, and new water temperatures will allow for the invasion of nonnative
fish species (Mohseni et al. 2003). Pacific salmon, which migrate to and spawn in some
mountains, have experienced population fluctuations related to climate (Downton and
Miller 1998). In the Columbia River system, the projected impacts of global warming are
warmer water temperatures and earlier snowmelt peak flows, which are likely to fur-
ther impact the beleaguered salmon populations and related ecosystems (Miller 2000;
Mote et al. 2003).
Land-use changes in mountains, especially urbanization, logging, and hydrolake (i.e.,
lakes created for power generation) development can have significant impacts on re-
gional and microclimates in mountains (McGowan and Sturman 1996a; Godde et al.
2000; Mote et al. 2003). These environmental disturbances can have long-term influ-
ences on climates since they change the surface characteristics as well as energy and
moisture fluxes. Hydrolakes have been found to moderate temperatures, increase at-
mospheric water-vapor content and precipitation, and increase windiness by decreas-
ing surface roughness and developing their own wind systems (McGowan and Stur-
man 1996a). Snowmaking is an adaptation strategy for ski resorts facing declining
snowpacks, but it can alter local hydrology and climate (Steiger and Meyer 2008).
Because of their slope, aspect, verticality, mass, and altitude, mountains are partic-
ularly sensitive to changes in climate; they have been called some of the best natural
“barometers” and predictors of global climate change consequences in the world (Ben-
iston 2006; Rhoades 2006; Barry 2008). Changes in mountain environments are import-
ant not only within the mountains, but also in terms of the resources and services they
provide to adjacent lowlands. Frequently cited in the press and growing climate change
literature is the retreat of the world's glaciers that has occurred over the past century,
most noticeably in the tropics and subtropics. This rapid melting of snow and ice has
resulted in an increase in the formation of high-altitude glacial lakes, sometimes too fast
to monitor accurately, increasing the potential for catastrophic down-valley floods that