Climate change enlarges total fertile area while reducing prime locations, C4 replaces C3

  Climate change negatively affects the growing season for areas in the mid latitudes traditionally associated with farming & wheat production (in part due to more super wet regions, change in night temperature, wild shifts in temperature over a short period of time) but it does enlarge the total land area globally able to be used for growing through a warming of the northern latitudes (shifts precipitation over to rain from snow).

In Western Canada for example in 2010 more than half of the lower latitude regions of the key provinces of Manitoba and Saskatchewan received more than two feet of water in the fall alone, that's more than what all of Western Canada usually averages per year. This presents new problems; In Canada for example by 2050 optimal growing conditions will shift to as far north as the Canadian Shield where for the last century the area has been infertile or at the very least, difficult to grow vegetation on. Photosynthesis shifts from C3 to C4 allowing for better water efficiency use and faster carbon dioxide intake (important since CO2 levels are also rising). Under phosphorous stress both C3 and C4 plants show similar biomass production even though the root to shoot ratios are not the same.

C3 - Only enzyme used (rubisco) is also involved in CO2 uptake. Better than C4 under temperate conditions (cool/avg light intensity).

C4 - CO2 initially incorporated into 4 carbon compound. Differs from C4 since it makes use of both rubisco and pep carboxylase (pep is responsible for both the uptake and delivery of CO2). rubisco ends up preocupied with CO2 deliveries from pep and so it does not have the opportunity to also take in o2 for photorespiration. pep is also faster than rubisco at taking in co2 and that means stomata aren't open as long (less water ends up transpired and so C4 is more efficient at photosynthesis in less moist conditions).

-More co2 is absorbed, less water is used, photosynthesis only takes place within a specialized part (kranz cells), an anatomy feature unique to C4 plants; that makes C3 photosynthesis simpler and less energy intensive.
-C4 plants end up with a higher shoot to root ratio (better suited to high light intensity/competition for light becomes more of a factor).

root (supportive tissues)/shoot (growth tissues) ratio - decreases with plant size, changes according to nitrogen availability (fertilizer).