The park’s bedrock is made up of Separation Point Granite. Its physical and chemical qualities determine the nature of the forest cover and details, such as the colour of beaches and stream beds.
Soils developed from granite bedrock are relatively infertile, yet damp gullies just above sea level support rich forest. Although many trees were removed during the milling era, a lush understorey of trees and shrubs, tree ferns, kiekie and supplejack remains and the gullies lead the regeneration process.
Black beech is the natural cover of the dry ridges and headlands close to the sea, with hard beech further inland where more moisture is available. Kanuka occurs where there have been windfalls or a history of fires. Manuka occurs where repeated burning has degraded the soil.
D’Urville found South Island kokako in the forests around Torrent Bay; these and several other native bird species have since disappeared and bellbird, fantail, pigeon and tui are now the main forest birds. Around the beaches, estuaries and wetlands, pukeko are common.
A range of wading birds stalk the estuaries for fish and shellfish, while offshore, gannets, shags and terns can be seen diving for food. Little penguins feed at sea during the day and return to burrows on the park’s islands at night.
In 2007 Abel Tasman Birdsong Trust was formed whose vision is to have the forests and beaches of Abel Tasman once again filled with birdsong. You may see the trusts stoat and possum traps on or near the track in Torrent Bay. The traps are regularly checked by volunteers so don't touch the traps and if you see a dead animal tell the next DOC ranger you see.
Rivers and estuaries
The native fish communities within Abel Tasman waterways are almost pristine, due to the relatively intact nature of the parks catchments. Close proximity to the sea, also means they are within easy reach of whitebait and other migratory native fish larvae.
Fourteen native fish species have been recorded, including threatened migratory galaxiid species, such as short-jaw, and giant kōkopu, kōaro and inanga. Banded kōkopu (not threatened) are often seen in small pools, if you are quiet.
Unmodified estuaries are an integral feature of the Abel Tasman Coast, always changing as the tides come and go twice a day. The regular influx of nutrients from the sea supports many fish, snails, worms, and crabs, which are food for coastal birds. Being sandy (rather than muddy) the park’s estuaries are easily explored around low tide.
Areas inundated by only the highest tides carry salt marsh vegetation: rushes, glasswort and sea primrose. These plants trap moving sand, often beginning a long process which can result in replacement of the estuarine community with a terrestrial one.
Beyond the shoreline
The park’s rocky coastline is a fascinating place to explore, particularly with snorkel and goggles. Between the tides, plants and animals occupy distinct bands like the forest zones between sea level and the bushline. Periwinkles, tubeworms, neptunes necklace and pink algae are all adapted to a particular level of exposure to sun and wind.
Underwater, seaweeds are grazed by sea urchins and Cook’s turban shells. Further out are granite reefs, while at Separation Point live bryozoans, tiny animals that build extensive colonies of coral-like structures.
Fur seals are found along the coast of the park, particularly on the more remote granite headlands of Separation Point, Tonga Island and Pinnacle Island.
Tonga Island Marine Reserve runs one nautical mile out from the coast between Awaroa Head and the headland separating Bark Bay and Mosquito Bay. All marine life within its boundaries is protected and fishing is not allowed. A separate publication on the reserve is available.