Over 150 hectares of forested land near Inangahua on the West Coast is set to become part of Paparoa National Park.
The area, to the east of the Paparoa Range in the Buller District, includes limestone cliffs that are regarded as very rare.
Associate Conservation Minister Nicky Wagner said the lowland podocarp and beech forest was also rare, as much of the region had been cleared for agriculture.
It is also a likely habitat for some plants including the declining scarlet mistletoe, and nationally threatened wetland plantain.
The views in the area were spectacular, Ms Wagner said.
"It's got fantastic limestone features... and then it's got low-lying basins as well. [It's] mostly a wetland - it's got springs and disappearing creeks ... it's a beautiful habitat."
The land was bought from a mining company by the Nature Heritage Fund, which was set up to acquire land in order to protect natural ecosystems.
Last year Environment Minister Nick Smith announced that the government was adding nearly 4000 hecatres of land surrounding the Pike River Mine site to the national park.
The new area would include a 45-kilometre walking route named the Pike29, in memory of the 29 men who died in the 2010 mine disaster.
The plan drew the ire of some of the victim's families, who said it would be like desecrating graves.