Climate Change and the Rocky Mountains - Impact of Global Changes on Mountains: Responses and Adaptation - page 445

recent summer temperature increases and wildfi re disturbances appear to
be allowing introduced rainbow trout ( Oncorhynchus mykiss ) distributions
to expand upstream, thereby enhancing the spread of hybridization with
native westslope cutthroat trout ( O. clarkii lewisi ) populations (Muhlfeld et
al. 2009, Isaak et al. 2012).
Aquatic invertebrates
Aquatic invertebrates are also important to regional biodiversity in Rocky
Mountain aquatic ecosystems. They are useful biological indicators of
climate-induced changes in mountain ecosystems because they are integral
components of aquatic food webs and their distributions and abundances
are strongly linked to temperature and stream fl ow gradients (Milner et
al. 2001). Species-specifi c distributions are likely to be profoundly affected
as temperatures continue to rise beyond species' thermal limits and
precipitation patterns change potentially causing some streams to become
intermittent. Elevational changes in the timberline associated with climate
change will also affect species' distributions and the structure and function
of stream ecosystems.
Cold-water stenothermic invertebrate species inhabiting alpine stream
environments in the Rocky Mountains are especially vulnerable to climate-
induced warming and snow loss. Recent data show increased magnitude and
rate of warming with extensive loss of glaciers and snowpack throughout
the Rocky Mountains. For example, the loss of glaciers in Wateron-Glacier
International Peace Park is iconic of the combined impacts of global
warming and reduced snowpack; 125 of the estimated 150 glaciers existing
in 1850 have disappeared, and the remaining 25 are predicted to be gone by
2030 (Hall and Fagre 2003). Changes in the hydrological cycle associated
with snow and ice loss are likely to warm perennial streams and some may
transition to intermittent fl ows. These changes threaten the stability of
sensitive ecosystems that provide critical habitat for alpine-restricted stream
invertebrates facing increased risks of extinction, such as the rare caddisfl y
Allomyia bifosa (Hauer et al. 2007) and the endemic meltwater stonefl y Lednia
tumana (Muhlfeld et al. 2011), Lednia tumana , discussed further under case
studies, is the fi rst invertebrate species that warrants the protections of the
U.S. Endangered Species Act (ESA) due to climate-change-induced glacier
loss. Genetic diversity in alpine invertebrates may be particularly sensitive
to temperature warming because many species are undergoing rapid range
shifts in these environments (Jordan et al. In-review).