Climate change!
Who would have guessed?....…
Just the other week, I had a discussion with a co-worker who REALLY, REALLY ought to know better but credited "Global Warming" with the spread of Kiwi fruit from just New Zealand to France, Italy, Israel, and places in between.
In fact, the driving force for this, and many agricultural expansions is the ability to irrigate new regions (Thanks, Israel). Plants are mainly dependent on sunlight/darkness and water availability.
Not that I'm trying to correct you, I get your post completely, but just in case some FReeper is encountered with my co-worker's idiotic opinion...