The Department of Conservation (DOC) is closing 21 walking tracks around kauri land to help prevent the spread the kauri dieback disease, Conservation Minister Eugenie Sage has said.

In addition, a further 10 tracks will be partially closed and open sections will be upgraded to eliminate wet and muddy sections of track.

This will better protect the roots of kauri trees, Sage said.

"As there is currently no proven cure for kauri dieback, the best way to protect our kauri is to slow and stop the disease from spreading," she said.

The closed tracks have a high risk of kauri dieback, low visitor numbers and high upgrade and maintenance costs.

Kauri dieback, a microscopic fungus-like organism, can kill kauri of all ages, according to DOC.

It lives in the soil and infects kauri roots, damaging the tissues that carry nutrients and water within the tree, effectively starving it to death.

DOC will be closing, or partially closing, tracks in Kaitaia, the Kauri Coast, Whangārei, on Aotea/Great Barrier Island, in Hauraki, Waikato and Tauranga.

The track closures are permanent and will be monitored.

"I appreciate some people may be disappointed by the closure of a favourite track," Sage said, "but I strongly encourage everyone to do the right thing and respect the track closures to reduce the risk to kauri forests."

The decision was made after public consultation and the majority of submissions were in favour of the closure of the tracks, Sage said.

She said the closures may be reconsidered if additional science and other information provide certainty that public access would not cause any risk to the trees.

Kauri are among the world's largest trees, growing to more than 50m tall, with trunk girths up to 16m – they can live for more than 2000 years, DOC says.