East River St. Marys Nature protects a patch of intact forested floodplain in the midst of a highly modified, biologically productive agricultural landscape at the southern extent of Pictou County.

The nature reserve supports white elm and ironwood, both uncommon tree species in Nova Scotia. It also provides habitat for wood turtle, a listed species at risk. The nature reserve is one of the only publicly owned parcels of land on the East Branch of St. Marys River.