Over 90% of the nature reserve is rainforest. It is an important intact remnant of the floodplain rainforest that once covered the banks of coastal rivers in northern New South Wales. The reserve is also an important roosting and breeding area for flying foxes.
Local Aboriginal women have a close and ongoing association with the island and its rainforest. A group of Aboriginal women, Nyami Julgaa, is recognised and acknowledged as the cultural custodians of Susan Island.