Fig. 2.

ACC has driven an increase in precipitation in much of the more northerly latitudes (IPCC, 2014). This has, in turn, driven complex responses in wild plants. Mountain hemlock (Tsuga mertensiana) has shifted the centre of gravity of its distribution to lower elevations in California (a 255 -m downwards elevational shift), in spite of an increase in mean annual temperature of 2·85°C during the study period (1930s to 2000s). The observed downhill shift, while counter to expectations from warming, was in concert with a decline in water deficit of 134 mm over the past 70 years (Crimmins et al., 2011). Photo is courtesy of Charles Webber © California Academy of Sciences.