Following the Ice Age, sea levels had stopped rising and the coastline reached its present position about 6500 years ago. The coastline was now some 15km west of its position at the height of the Glacial Period when sea levels were at ther lowest, which meant that a large area of land had been inundated by sea. Aboriginal communities such as the Cadigal and Wangal people were resourceful in the way that they were able to utilise the environment.

During recent times Attenbrow suggests that the vegetation consisted mainly of eucalypt forests and woodlands in addition to heaths, freshwater swamps and estuarine saltmarsh and some mangrove communities.

In the southern region such as in Royal National Park, areas of closed forest were limited - though rainforest species occur in sheltered sandstone gullies in many forested areas. Rainforest areas were reported to have occurred at Eastwood around Port Jackson.