Protein food with low impact on the environment

is insects says this article from Discover magazine. Excerpts:
"Raising insects has a low impact on the environment. They require little water, perhaps because they obtain much of their moisture from their food. It takes 869 gallons of water to produce a third of a pound of beef, about enough for a large hamburger. By contrast, to supply water to a quarter pound of crickets, Gracer simply places­ a moist paper towel at the bottom of their tank and refreshes it weekly. Insects, he says, also need less food and space than vertebrate sources of protein and therefore could replace or supplement food resources that may become scarce in the future, such as fish stocks, which a recent study indicates may collapse by 2048.
...........
...in Botswana and Zimbabwe, insect gathering is becoming commercialized. And rural villagers in southern Africa harvest caterpillars from the local mopane trees. Traditionally, mopane caterpillars have been an important source of protein for the villagers, but more recently they have also been packaged and sold as a regional delicacy.

In fact, at least 1,400 species of insects are eaten around the world, and the practice dates back thousands of years. However, even commercially distributed species such as the mopane caterpillar are harvested from wild insect populations, meaning that they are subject to year-to-year fluctuations and problems of overharvesting."
One of the enthusiasts is David Gracer who teaches expository writing. "Gracer continues to spend much of his spare time speaking at museums and schools about the benefits and joys of bug eating. In the long term, though, he has grander plans: He would like to import edible insects such as the popular mopane caterpillars or set up a commercial operation selling insects already available here, such as spicy Mexican grasshoppers, or chapulines. He knows his mission is not an easy one; for one thing, there is the small matter of funding. “If I did this for a living, my family and I would be eating bugs all the time,” he says."