Kauri

Agathis australis is endemic to the North Island of New Zealand.

• Found in the northern half of the North Island, from the Far North District south to approximately latitude 38°S (northern Waikato and Bay of Plenty)
• Once formed vast, continuous forests across much of the North Island before extensive logging in the 19th and early 20th centuries
• Grows at elevations from near sea level to approximately 400 meters
• The species is a relic of the ancient Gondwanan flora, with ancestors dating back over 200 million years
• First described by the French botanist Achille Richard in 1834 as Dammara australis, later transferred to Agathis
• The largest remaining kauri forests are in the Waipoua Forest, Trounson Kauri Park, and the Waitakere Ranges
• The genus Agathis comprises approximately 21 species distributed across the Southwest Pacific, from New Zealand and Australia to Malaysia and the Philippines

Agathis australis is a massive, long-lived evergreen conifer with a distinctive pale gray trunk and broad crown.

Size:
• Typically 30 to 50 meters tall, with the tallest known specimens reaching 55 to 60 meters
• Trunk diameter: 1 to 5 meters, with some ancient trees exceeding 7 meters
• The trunk is remarkably cylindrical and often unbranched for the first 15 to 30 meters
• Crown is broad, rounded, and open, with spreading branches emerging high on the trunk

Bark:
• Characteristic smooth, pale gray to silvery-gray bark that sheds in thick, leathery flakes
• The bark of young trees often bears distinctive "bark bubbles" or resin blisters
• Bark shedding helps the tree shed epiphytes and climbing plants

Leaves:
• Broad, leathery, ovate to lanceolate, 3 to 7 cm long and 1 to 2.5 cm wide
• Dark glossy green above, paler beneath
• Leaves of juvenile trees are larger and more narrow than those of mature trees
• Arranged spirally but often appearing two-ranked on young branches

Cones:
• Male cones: cylindrical, 2 to 5 cm long, borne on branch tips
• Female cones: globose, 5 to 8 cm in diameter, greenish, maturing over 2 to 3 years
• Cone scales detach individually at maturity, releasing winged seeds
• Seeds are small, approximately 1 cm long with a membranous wing

Kauri is a keystone species of the lowland and montane forests of northern New Zealand.

Habitat:
• Grows in warm, humid, subtropical to temperate maritime climates
• Prefers fertile, well-drained volcanic soils, particularly on basalt-derived substrates
• Often found on ridgelines and upper slopes where the massive crown can access full light
• Once formed extensive mixed forests with other native trees including tōtara, rimu, kahikatea, and tānekaha
• Receives 1,200 to 2,000 mm of annual rainfall in its native range

Ecosystem role:
• A keystone species that supports entire ecosystems of epiphytes, mosses, lichens, and invertebrates in its massive crown
• The bark-shedding habit creates a unique "kauri snail" habitat and supports specialized invertebrate communities
• Fallen kauri leaves create a distinctive, thick, acidic leaf litter layer that influences understory composition
• Kauri groves support unique plant communities adapted to the nutrient-poor, acidic soils they create
• Seeds are dispersed by wind and consumed by native birds including the North Island kōkako and kākā
• Ancient kauri trees serve as critical nesting platforms for large native birds

Kauri faces a severe and ongoing conservation crisis from kauri dieback disease (Phytophthora agathidicida), a devastating soil-borne water mold discovered in 2008 that kills kauri of all ages.

• Kauri dieback has been confirmed in many of the remaining kauri forests of the North Island, including the Waipoua Forest, home of Tāne Mahuta
• The pathogen infects roots, damaging the tree's vascular system and causing crown dieback, lesions, and eventual death
• There is currently no known cure — infected trees inevitably die
• Spreads primarily through soil movement on human footwear, vehicles, and animal hooves
• The New Zealand government and Māori iwi have established strict biosecurity measures, including cleaning stations and track closures in kauri forests
• Visiting kauri forests now requires scrubbing footwear with disinfectant before and after entry
• Over 90% of the original kauri forest was logged between 1840 and 1970, making the remaining stands even more precious
• Tāne Mahuta, the largest known living kauri (estimated at 1,500 to 2,500 years old, 51 meters tall, 13.8 meters girth), is protected in Waipoua Forest and is a site of deep cultural significance to the Māori
• The IUCN Red List classifies kauri as Endangered