A naturally bounded, ecologically distinct geography: a watershed is one example. Term coined by Peter Berg and Raymond Dasmann. The largest bioregion is an ecoregion (example: the Ozark Plateau), the next largest a georegion (river basins, mountains, watersheds), and the next a local morphoregion. As Berg described it:

A bioregion refers both to geographical terrain and a terrain of consciousness--to a place and the ideas that have developed about how to live in that place. . . A bioregion can be determined initially by use of climatology, physiography, animal and plant geography, natural history and other descriptive natural sciences. The final boundaries of a bioregion, however, are best described by the people who have lived within it, through human recognition of the realities of living-in-place. . . .