Photosynthesis drives it. Not consumption. The Chatham spleenwort obtains energy from sunlight and nutrients from sea spray and rock weathering. This halophytic adaptation allows it to thrive in nutrient-poor coastal environments where other plants struggle. It reaches about 15 centimetres in height with narrow leathery fronds that resist salt damage. The species inhabits coastal cliffs and rocky outcrops on the Chatham Islands. It prefers windy exposed sites where salt spray provides essential minerals. Unlike mainland ferns that require sheltered conditions, this species has adapted to harsh maritime environments. Fronds are thick and leathery, coloured dark green, with a waxy coating that repels salt. Spores are produced on the underside of fertile fronds in linear sori. These spores are released into the air, drifting on strong winds between islands. Classified as Nationally Critical, Chatham spleenwort faces an extremely uncertain future. Its distribution is extremely limited, confined to the Chatham Islands. Invasive species such as rats and cats threaten seedlings and spores. Habitat modification from historical human activity has reduced suitable coastal habitat. Climate change may alter wind patterns affecting salt spray distribution. Each threat compounds the others. Chatham spleenwort has nowhere else to go. It is endemic to these islands. If it disappears here, it disappears everywhere. Conservation efforts focus on eradicating invasive predators and protecting remaining coastal habitat.