When comparing the growing zones in Canada, Europe, and United States, it's pretty amazing when you consider the diversity we have in the USA. Canada does food production is limited to the most southern regions and thin coastal areas. Europe's growing zones are wide encompassing whole countries in a single zone. The zones seem to mimic the innermost shapes of the continent. Distance from the large ocean masses drives the extreme cold temperatures.
As our growing zones shift in the next 50 to 60 years, I can only wonder how we will adapt. Keep in mind as the warmer climates shift north in the United States, it does not change the sunlight. The northern latitudes will still have short days in winter, not to forget the intensity of the light is diminished as much as 40%. Our annual crops will be less affected by water availability than our perennials and trees which require a cold season.
Some researchers suspect that the Atlantic conveyor, the Atlantic ocean currents which cycle North from the equator across Europe coastlines could stall and cause a reduction in continental temperature.
in all of this I hope we will increase the diversity of plants and work towards facilitating the ecological adaptation.