Flora: Currently, there is a vegetative mix of natives and weeds, established with plantings of native wetland vegetation since 1987. Extensive saltmarshes dominate the lower, tidal edges of both islands. These areas are typically covered with salt-tolerant plants such as samphire species (Tecticornia spp.) and other chenopods. These halophytic shrubs and succulent herbs play a critical role in stabilizing sediments and providing habitat for estuarine fauna. Fauna: Boundary Island and surrounding sand bars are a focus of occurrence by a suite of migratory shorebirds (e.g. plovers, knots, godwits) that were not regularly recorded elsewhere in the estuary. Nesting pied oyster catchers, osprey, and other waterbirds are regularly observed on the island. Historically, the increased tidal range resulted in more frequent inundation of Nirima Cay, a former a nesting site to Australian pelicans. Hence, Boundary Island a major nesting site for a diverse variety of waterbirds. The site is subject to frequent disturbance by people (boating, camping, dogs), which have the potential to disrupt the ecological dynamics of breeding birds. DBCA officers confirm the site holds conservation value, being a haven for migratory bird feeding.

Boundary Island was created from dredge spoil from when Sticks channel was enlarged in 1987. Boundary Island is 25 hectares and 5m above sea level. Boundary and Channel Island primarily consist of estuarine and coastal sediments, including sandy sediments derived from coastal dune systems and river deposits. Silty clay sediments from fine particles were deposited by the Peel and Murray Rivers along with tidal movements.