Keep an eye on jatropha - if this is half as good as they say, I'd say we'd be fools not to look into places where it can be planted. A lot of our farmers here in Western Australia in the last few years have discovered how much the drought can suck.
I'm not advocating turning a whole property over to jatropha production - again, as for the Mali farmers, food production should not suffer for fuel crop production - but in a drought, a crop that can produce income without needing the guaranteed rainfall might not be a bad idea...
Now for the negatives. Haven't we learned from cane toads and rabbits and tilapia? But apparently the Mali farmers manage to grow it between rows of crops, and that gives hope that it would be controllable. Also, I'm thinking of one other "weed" that I've found a use for.
Growing wild over enormous amounts of the land here are these small yellow melons, which are treated like a weed and which grow pretty much anywhere, unassisted. You can cook them into a pretty flat tasting melon pie, but the real value of them is in the seeds.
See, the seeds are similar to pumpkin seeds, and when dried and roasted, are a snack that seems to be rich in antioxidants and may possibly be an addition to the Body Friendly Zen Cookbook diet. Pumpkin seeds are one suggested food that helps our bodies to reverse cancer, but the seeds have tough outer shells and that means either nasty chewy splintery bits when roasted, or a lot of hard work hulling the seeds before roasting.
The pigmelon seeds have thinner outer coverings. Also, with pumpkins, you need to get the seeds when pumpkin is being processed, or grow pumpkins especially for seed. These pigmelons are pretty much good for nothing else but their seeds, except that the pulp and stems and leaves would make a good return to the soil of organic matter - since you're extracting the seeds, you can be pretty sure the plant won't get away under your crop because there's no seeds to grow from.
So it makes sense to me to grow some of the things that don't need precise rainfall and pH and NPK ratios, during the worst years of drought, and revert to mostly food crops and a bit of "insurance cropping" during the better years. And if demand for these products grows, who knows we may open up a whole new belt for more eco-sensitive farming.