The major ‘natural bioregions’ of the Hunter subregion – as classified by the Interim Biogeographic Regionalisation of Australia (IBRA) – are the Sydney Basin (mainly Hunter, Kerrabee, Wyong, Yengo and Wollemi IBRA subregions) and the Brigalow Belt South (mainly the Liverpool Range IBRA subregion). The Hunter Valley is of great ecological significance because it represents the only major break in the Great Dividing Range, which provides a link between coastal and inland NSW, and includes an overlap between tropical and temperate climate zones. The lower Hunter Valley contains the Ramsar-listed Hunter Estuary Wetlands, as well as Port Stephens and Lake Macquarie. The Hunter subregion contains 27 endangered ecological communities, eight endangered populations, 116 threatened animal species listed under the NSW Threatened Species Conservation Act 1995 (the TSC Act), of which 33 are also listed under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act), and 86 threatened plant species listed under the TSC Act, of which 50 are also listed under the EPBC Act. The EPBC Act also lists 39 species of migratory birds. Twelve groundwater-dependent ecosystems have been identified in the Hunter subregion, including wetlands associated with Newcastle, Sydney Basin, Tomago and Lower Goulburn River aquifers.