Huh, what? You must be kidding. Where do you come up with this stuff?
Lets look at America. The total amount of land used for farming dropped from 1.2 billion acres in 1950 to .95 billion acres today (a 20% decrease) while total crop yields rose drastically. This reduction in farming land occurred EVEN though vast portions were turned over for non-food (ETHANOL) production! If you are really worried about food shortages why are global warming supporters ACTIVELY supporting measures that negatively impact food production?
In 1870, 70-80% of the American population was directly involved in farming, that number is now less than 2%. Remember, some of that 2% is involved in ETHANOL creation and not food creation at all.
I am aware of nothing that supports your assertions other than models created out of the vivid imaginations of one climate scientist or other. The objective evidence certainly suggests and possibly proves the exact opposite.
http://en.wikipedia.org/wiki/Agriculture_in_the_United_States
http://www.livinghistoryfarm.org/farminginthe50s/life_11.html
If you ever take a road trip you may notice the many housing developments build on what used to be prime farm land and accounts for the decrease in crop land. And you may also notice the fence rows disappearing as cash crop farmers buy up smaller farms. And the huge cultivating, planting and harvesting equipment used by those few farmers to work the land.