The lowland areas are quite highly populated and therefore urban development, agriculture and forestry are a major threat to natural habitats there. One block of lowland forest remains in and around Whanganui National Park and large areas of the uplands are protected either by Maori tradition or in national parks of which Te Urewera is the largest. The four North Island national parks, which surround the plateau, are Te Urewera, Whanganui, Egmont and New Zealand's first national park, the World Heritage listed Tongariro National Park. Introduced species and livestock grazing are now major threats to some endemic species. Rats, cats and stoats prey on native reptiles and birds (including the kokako, blue duck and brown kiwi), while imported plants such as old man's beard, banana passionfruit and gorse can take over from indigenous species. Finally grazing by goats and possums can eradicate others such as kamahi, kaikawaka ("Libocedrus bidwillii") and mountain tōtara. Therefore, smaller islands off the coast of Wellington have been used as a refuge for North Island birds and reptiles whose habitats may be threatened now or in the future.