Kauri tree disease disrupts forest carbon storage in New Zealand

New research shows that severe kauri dieback disease can cause New Zealand forests to shift from storing carbon to losing it, with the heaviest impact falling on mature trees.

The Study

Researchers revisited study plots in the Waitākere Ranges that were first surveyed between 2011 and 2014 to measure changes in living biomass and carbon storage over a decade. Study co-author Toby Elliot and the research team assessed tree canopies and tracked which trees had died. The disease itself is caused by the soil-borne water mould Phytophthora agathidicida, which infects roots and stops trees from taking up water and nutrients.

Carbon Losses

The study found that healthy forest stands gained about 0.8 tonnes of carbon per hectare each year, while stands showing signs of dieback lost about 0.1 tonnes. Severely affected stands lost around one tonne of carbon per hectare each year. Mature forest plots held an average of about 248 tonnes of living carbon per hectare, compared with about 88 tonnes in younger, regenerating forest. Kauri contributed about half of the living carbon where they were present.

Context

Kauri trees are long-lived taonga of deep cultural and spiritual significance to Māori, with individual trees like Tāne Mahuta standing for centuries. Protecting these forests is a key conservation priority supported by groups like Te Kawerau ā Maki. Visitors can help prevent the spread of the disease by staying on marked tracks and cleaning their footwear.