Only 700-750 hectares of remnant vegetation remain in the catchment mostly scattered along the fringes of local creeks. These remnants vary in size from the large reserves such as Lake Parramatta and Excelsior Reserve to a small isolated fragments less then one hectare. Most of these remnants are of significant conservation value. Most of the smaller fragments are highly degraded and all are under constant pressures from the urban environment.

Renmant vegetation is mainly threatened by clearing for new developments, weeds and altered drainage and poor management practices.

Many organisations are involved in improving vegetation quality in the catchment. The Trust has helped to develop the Green Corridors Vegetetion Management Strategy, provide grant funding of $200,000 each year for vegetation projects, developed a partnership with Department of Corrective Services to provide labour for weed control and revegetation projects and community education activities.