Several regionally rare plants grow here, such as trailing ground pine, pagoda dogwood and purple duckweed. Due to its diversity of habitats, a variety of birds forage and nest here, including state and regionally rare species such as the least bittern, black-billed cuckoo, pied-billed grebe, American coot and field sparrow.
A total of 187 vertebrate wildlife species have been found here, including beavers, muskrats, deer, masked shrews, thirteen-lined ground squirrels, garter snakes and northern leopard frogs. Poss Lake is an underutilized fishing spot, and recent surveys have found good numbers of bluegill and largemouth bass. Prairie crayfish, giant floaters and red admiral butterflies are some of the many invertebrates that call the site home.
Although Big Woods is undeveloped, the Batavia Spur of the Illinois Prairie Path runs through a southern section of the forest preserve.