The minute you start looking for maps of your bioregion, you will discover the frustrating inadequacies of most existing ones. Street maps obscure the geographical features. Topographical maps ignore the vegetation. Vegetation maps leave out the historical sites.
Watershed maps stop abruptly at county, state, or national borders, even though the water flows on.
Consult Boundaries of Home , edited by Doug Aberley, for a useful introduction to bio-cartography.