There are extensive areas of unmodified silver beech, red beech, and valley floor podocarp forest, alpine tussock lands, alpine wet turf and sub-alpine sphagnum bog. It is one of the few areas in the region containing southern rata, a species endangered by possum browsing. The forest is home to a great variety of indigenous forest birds, including the rare kaka, kakariki and NZ falcon (karearea).
Greater Wellington manages the Hutt Water Collection Area carefully,controlling possums and other animal pests to protect the rich variety of plant, fish, insect and bird species that make up the forest ecosystem. We use vegetation plots, exclosure areas and animal abundance plots to monitor vegetation response and animal numbers in the area. Photo points provide a record of vegetation changes at specific sites.