http://www.ewashtenaw.org/government/departments/parks_recreation/napp/pr_natac.html

Washtenaw County's Natural Areas Preservation Program (NAPP) purchases unique natural areas to ensure their preservation for the benefit of all County residentsplants, animals and people! The Washtenaw County Parks & Recreation Commission manages the program, identifying and caring for lands with special ecological, recreational, and educational benefits. The NAPP nature preserves are open to the public from dawn until dusk daily.

A list of properties.