Week 2 reading for this online course includes "Chocolate berries! Gingerbread plums!" from New Scientist (2009-11-7), describing how a World Agroforestry Centre program has helped people in Africa learn to domesticate, graft, and grow wild fruit trees. I'm in favor of anything that increases global crop diversity, since reliance on too few crops puts our food security at risk. And this program is dramatically improving the lives of some farmers.
But is this just another pyramid scheme? The formerly-poor farmer now "earning enough... to pay school fees for four of his children" is mainly selling trees to other farmers, not fruit. I assume there's some market for the actual fruit, but once all the trees he sells starting bearing fruit, will prices collapse, as they did for tulips and ostriches?
Here in Minnesota, there's some excitement about growing "pennycress" as an oil crop. It's also known as "fanweed" and "stinkweed", under which names we learn that it can be poisonous to livestock. But what worries me is that the "only commercial market for the crop is with Pennycress Energy Company LLC (PEC)." How many farmers would need to jump on the pennycress bandwagon before supply exceeds demand, prices collapse, and they're left with a problem weed rather than a valuable crop?
David Marks emails that it may be possible to use mutagenesis to "reduce weedy characters (such as secondary dormancy, seed glucosinolate accumulation)." That seems plausible, in which case pennycress may have potential as a future crop, at least in areas where it can fit between corn and soybean in a rotation (reducing erosion and perhaps suppressing weeds) and still reliably produce seed. In the years it takes to develop a nonweedy version, changes in subsidies or improvements in other alternate-energy technologies might undermine its value as a biofuel, but there might be higher-value uses as a chemical feedstock. Current promotion of this weedy "crop" seems premature, however.