The Lake Rototoa – Te Rau Pūriri biodiversity focus area is situated towards the northern end of the South Head peninsula. It has the largest and deepest dune lake and the largest dune forest remnant on the peninsula. Raupō reedland and Machaerina sedgeland wetlands are found here, along with freshwater streams creating a connection to the inner Kaipara Harbour.
The biodiversity focus area includes Lake Rototoa Scenic Reserve, administered by the Department of Conservation and Te Rau Pūriri Regional Park, administered by Auckland Council.
Lake Rototoa is of high biodiversity value. It is recognised as a Significant Ecological Area and an Outstanding Natural Feature in the Auckland Unitary Plan.