Climate Change and the Rocky Mountains - Impact of Global Changes on Mountains: Responses and Adaptation - page 441

Aquatic Biota in the Rocky Mountains
Climate change is rapidly altering the structure and function of aquatic
ecosystems across the Rocky Mountains of North America. Although the
effects of climate change vary across a variety of spatial and temporal
scales, warming trends and climate model simulations indicate that stream
habitats will become warmer, have more variable thermal and hydrologic
regimes, and will be more susceptible to stochastic disturbances such as
fl ooding, wildfi re and drought (Jentsch et al. 2007). Combined with existing
stressors of habitat loss and invasive species, climate-induced changes in
precipitation and air temperature are predicted to have signifi cant effects
on the distribution, abundance and phenology of many aquatic species
(Walther et al. 2002, Parmesan and Yohe 2003). This is particularly true for
cold-water, stenothermic species (e.g., fi sh and invertebrates) inhabiting
mountainous streams. These species show strong temperature and fl ow-
related range contractions and thus are potentially the most threatened
groups of species due to impending climate change (Milner et al. 2001,
Parmesan 2006). As climate warming rapidly progresses throughout the
Rockies, aquatic biota must adapt in place, shift to track suitable habitats
(i.e., climatic niches) or be extirpated.
Salmonids
Native salmonids (e.g., trout, char and salmon) are a group of fi shes with
considerable ecological and socioeconomic significance in the Rocky
Mountains. Salmonid fi shes are especially vulnerable to the effects of
environmental change in freshwater systems because they require cold,
connected and high-quality habitats, which are easily fragmented by
changes in thermal and hydrologic regimes (Williams et al. 2009, Haak et
al. 2010). Moreover, many populations have experienced large reductions in
historically occupied habitats over the past century, owing to anthropogenic
activities such as habitat degradation, fragmentation and invasions of
non-native fi shes (Paul and Post 2001). Consequently, many remaining
populations are small in numbers and isolated in headwater streams,
where they are at risk of extirpation due to environmental (e.g., fl ooding
and wildfi re) and demographic stochasticity and loss of genetic variability
(Peterson et al. 2008). Rapid water temperature increases throughout the
Rocky Mountains combined with these existing stressors have already
made it possible to see how a changing climate has been affecting streams
habitats with potential consequences for fi sh populations (Isaak et al. 2012).
Climate changes, therefore, could directly or indirectly lead to increasing
habitat and population fragmentation and accelerated decline of extant
populations inhabiting the Rocky Mountain region. These environmental