The dividing line between Ohio’s limestone bedrocks of the west, and the younger sandstones and shales of the east, runs through the center of the Arc. Bedrock is the womb of diversity — the more types of bedrocks exposed, the richer the flora.

The Arc covers five counties: Highland, Adams, Pike, Ross, and Scioto. Adams County is the only county in Ohio that has unglaciated limestone bedrock. The region harbors a unique and ancient ecosystem known as the alkaline shortgrass prairie — a rich & complex community that is globally rare.

Adams County has the highest listing of rare and endangered species in the state, when rated among all of Ohio’s non-metropolitan counties.

In the southern reaches of the Eastern Deciduous Forest, the number of native animal species increases dramatically, especially among mollusks, fish, amphibians, and reptiles. Ohio’s two southern-most counties — Scioto and Adams — have the highest zoological biodiversity in the state.

The Arc is blessed with four exceptionally clean river systems: Ohio Brush Creek, Scioto Brush Creek, Sunfish Creek, and the Rocky Fork. Two of them, the Scioto Brush Creek and Sunfish, have not only retained their original zoological diversity but have features that are promising for the watershed’s continued health: high forest cover, low human population, absence of dams, and almost no industrial and agricultural development.

The five-county region is relatively undeveloped and is blessed with compelling natural scenery, historic sites, and parklands. The Arc, if promoted as an eco-tourist destination, would bring fulfilling and much needed jobs to the geographic area.

Ross, Pike and Scioto Counties compose the central axis of the densest forest canopy  left in the state — land dissected by Ohio’s largest interior river, the Scioto.

The Ohio River, historic corridor of plant and animal migration, bisects the Arc along its southern-most boundary. It assists diversity in moderating the climate, increasing moisture, and affording migration of plant and animal species.