A new study published by Nature magazine indicates that the length of the growing season worldwide is increasing not just from warming temperatures but also from the direct influence of carbon dioxide.  This research, based on plot trials on grasslands in Wyoming, shows that  carbon dioxide affects plant growth by regulating evapotranspiration from leaves as well as direct fertilization.  The change in the length of the growing season varies from one species to the next and could have both positive and negative impacts depending on the effect on pollinators and competing species.  You can read more about this by clicking here.