It seems curious that we know so much about sheep, so little about those animals which outweigh them per hectare by factors of ten or a hundred times, and that we do not investigate these matters far more seriously. Our most sustainable yields may be grubs or caterpillars rather than sheep; we can convert these invertebrates to use by feeding them to poultry or fish. We can't go wrong in encouraging a complex of life in soils, from roots and mycorrhiza to moles and earthworms, and in thinking of ways in which soil life assists us to produce crop, it itself becomes a crop.

chapter 8.12 - Permaculture: A Designers' Manual (1988)