In Latin America and the Caribbean, these heat extremes and changing rain patterns could lead to a 70 percent fall in soybean crop yields and up to 50 percent for wheat by 2050 without further adaption efforts. In the Caribbean, tropical storms and sea level rise will impact everything from tourism to security.The immediate solution to the predicted problem is "don't depend on 4 crops for 80% of your calories". The human population of the planet has become far too dependent on corn, wheat, soy, and rice. Each one has major problems in store if the predictions of the climate scientists prove right. Much of the rice crop is grown on land not far enough above the high tide line; a couple feet of sea level rise is going to take out a lot of rice acreage. Although corn is a warm weather plant, it can easily get too warm and too dry and then that crop will fail as well. Wheat has been grown on land in dry areas, just a little bit drier, and down go the wheat yields.
Much of the effort of the Green Revolution was to improve these crops to be able to solve the problem of world hunger. It was a great success of the 20th century, but it may have set humanity up for a catastrophic fall in the 21st. We need to be diversifying our food sources and learning how to grow new crops in new places. For example, potatoes in Greenland. A couple of decades ago, there wasn't enough of a growing season in Greenland to make a potato crop, but climate change has changed that. The potato harvest in 2012 was 100 tons, double that of 2008.
My own project in this area is to grow sorghum. This spring I got a 7 gram packet of sorghum seed, enough to plant three 40' rows. I don't have an exact number for the yield, but it was a few pounds, at least 700 grams, of that I am sure. Sorghum is not like corn, where you have one harvest at the end of the season and can then weigh the crop. I cut my first sorghum heads in August, and they continued to send up new seed heads until the first frost in November. The choice seed heads get saved for grain sorghum uses and what doesn't pass muster becomes chicken feed. I thought about cutting the stalks and trying to extract juice for making syrup, but for that you need to have a large amount of stalks to get a small amount of syrup. It would have been too much work for me to come up with a pint of syrup. But all those sorghum stalks didn't go to waste -- they make great guinea pig fodder. Dry them and shred them up with the lawn mower and the pigs can snack on them all winter.
I got a bag of jowar flour -- milled sorghum -- at the Indian grocery store and have been experimenting with it in the kitchen. It makes good tasting pancakes and crepes, but I haven't tried using it in any bread recipes. If I had to subsist on a large sack of grain sorghum, I think it would be eminently possible given all the tortillas, crepes, pancakes, and rotis you could make with it, let alone cooking it up whole as a rice substitute.
The closest most Americans get to sorghum grain is when they buy a sack of birdseed to stock the bird feeder. I think this may change in the coming years, especially since sorghum will succeed in producing a crop where corn will fail.