The 15% of species that did both (shifting northward by 113.1 km and advancing their flight period by 2.7 days per decade, on average, over a 20-year period) had the largest population increases, and the 40% of species that showed no response had the largest population declines.2.4.2.6 Observed Changes to Physiology and Morphology Driven by Climate Change Impacts on species physiology in terrestrial and freshwater systems have been observed, and attributed to climate change