Characteristics and Significance of a Sub-tropical 'Low Wooded Island': Green Island, Moreton Bay, Australia

Abstract

Green Island, Moreton Bay (latitude 27°25'S), lies 9° south of the highest latitude previously reported for low wooded islands, which are noteworthy among reef islands for their geomorphic complexity and rarity. Green Island's geomorphic and ecological characteristics closely resemble those of low wooded islands (LWIs) of the northern Great Barrier Reef. Those characteristics which differ from the northern Great Barrier Reef examples can be largely explained by biological response to the latitudinal temperature gradient and to the low energy environment. As a low wooded island 1 200 km south of the southern-most LWI on the GBR and close to the latitudinal limits of both coral reef growth and high mangrove diversity, Green Island may be unique. Previously, low wooded islands have been reported only from coral reef environments between latitude 18°N and 16°23'S, on high elevation reef flats close to mainland coasts. Although a serious threat to Green Island's geomorphic and ecological integrity (ie. coral dredging) has been averted, management provisions to ensure the preservation of this complex reef island require enhancement.