Also, is one person taking the car to go capture a handful of insects really less polluting than one cargo ship transporting tons of them? Proportionally?
The answer would depend greatly upon the variables. Not only is there the energy of transporting the food from Timbuktu to your city, but cultivated foods, be it bugs or bison, has to employ people who travel back and forth to work, and the feed and other supplies has to be transported, the waste material has to be disposed, ect. Leaving the total energy footprint many times greater than the final shipping amount.
I just drove my truck 68 miles and back, to pick up a sheep that was born on the farm and raised on pasture. Seeing that there is no feed energy expense, and I only used 7 gallons of gas to bring the animal home, I would say that my food is about as energy conserving as possible under the circumstances, though I personally dont buy into the CO2 from fossil fuels being the end of the world.
Its primarily out of frugality and food quality that I advocate locally sourced foods...and I will agree that driving many miles in a car to gather a few insects may not be the best use of fuel...though I would suggest that going on foraging forays where multiple food stuffs can be collected can indeed be worth the gasoline expenditure comparative to buying supper market goods.
I live in near so many great foraging areas... the Appalachia Mountains, the Kentucky river valley, Daniel Boone National Forrest, and scattered prairies are overflowing with food for those willing to get it. There are areas with plenty of grubs, beetles, worms, frogs, crayfish, snakes, fish, squirrels, deer....there are seasonal black berries, lots of wild greens, roots, and shoots, ect.
Personally I am spoiled on Fatty Mutton, back yard eggs, garden greens, and herbs. I will pay for other extras from our local co-op and farmers market, though by the end of this spring when my garden gets going, I plan to be 90% self sustained and locally supplied....as for the other 10%.....just cant give up taste for non local treats like coconut butter, lemons, sea weed, and the occasional ocean fish.