It is one of only two Northland west coast islands (the other being Wakatehāua Island, further down the beach)[5] and has unique terrestrial and marine habitats, including the most fur seals (oioi) in Northland (over 500), which probably also make it an important area for white sharks (mangō ururoa), seals being their main prey.

It also lives on the Aupōuri (golden-brown to dark olive) and Karikari Peninsulas (darker with more variable patterns), but was first identified on Matapia.

[4] Giant umbrella sedge (toetoe upoko-tangata) is in dense swards with occasional taupata and Parietaria debilis seedlings underneath.

On steep slopes iceplant (horokaka) and knobby clubrush (wīwī) dominate, with Chenopodium album (wild spinach) in patches above the coastal banks.

[4] Birds include white-fronted tern (tara), common diving petrel (kuaka), blue penguin (kororā), pipit (pīhoihoi), swamp harrier (kāhu), paradise duck (pūtangitangi), red-billed gull (tarāpunga) and welcome swallow.