some species over others. These changes may be particularly problematic for threatened and 
endangered species, the habitats of which are dwindling (McLaughlin et al., 2002), or those with 
limited dispersal capabilities if climate change makes their habitats unsuitable. Climate changes 
leading to increased rainfall or, conversely, drought may also shift invasive species ranges and 
present new opportunities for invasion. Climate change will also contribute to selective 
pressures on species, presumably leading to adaptive genetic changes that may influence species 
success (Barrett, 2000). 
Some species do not require climate change to damage ecosystems, yet climate change 
may exacerbate the damage they do cause. Two examples of invasive species that alter the 
invaded ecosystem even without climate change are the common carp (Cyprinus carpio ) and salt 
cedar (Tamarix ramosissima ). The common carp decreases water quality and destroys viable 
habitat for other desirable species while the drought tolerant and deep-rooted salt cedar 
dominates riparian forests that were once dominated by cottonwoods and willows (Charles and 
Dukes, 2007; Kolar and Lodge, 2000; Lite and Stromberg, 2005). Climate change may have 
positive feedbacks for both of these invasive species if waters warm in the midwestem and 
northern U.S. and if the southwestern U.S. experiences more frequent droughts, leading to an 
increase in the amount of suitable habitat to invade (Seager et al., 2007; Kolar and Lodge, 2000). 
This interaction between climate change and invasive species may intensify ecosystem effects 
and possibly increase the spatial extent of these effects. 
As temperatures and precipitation patterns shift in response to climate change, species 
ranges will also shift. A current example of a species shifting its range poleward and towards 
higher altitudes is that of the mountain pine beetle (Dendroctonus ponderosae). Historically, the 
range of the North American native mountain pine beetle has been limited due to climatic 
conditions; cold temperatures at higher altitudes and latitudes prevented the beetle from 
completing its life cycle in a single season (Logan and Powell, 2001). With increased warming 
at higher latitudes and altitudes the beetle is able to complete a life cycle in one season, allowing 
for range expansion, thus exposing new species of trees to pine beetle infestation and resulting in 
epidemic breakouts of the mountain pine beetles in existing and new environments (Carroll et al., 
2003; Logan and Powell, 2001). Although this is a terrestrial example, it illustrates two 
important points: (1) invasive species are already responding to climate change and (2) native 
species can become invasive when they spread into new locations as a result climate change 
(Mueller and Hellmann, 2008). This underscores the importance of considering climate-change 
effects since species responses and overall impacts may not be limited to the current set of 
known AIS. 
Currently, most examples of species’ range expansions in response to climate change are 
terrestrial (see Parmesan, 2006; Root et al., 2003; Walther et al., 2002) although aquatic 
1-8 
