Palmyra Atoll, an uninhabited scatter of 42 low-lying islets in the North Pacific, supports exceptionally intact coral reefs and a million seabirds, yet its native rainforest was heavily altered by introduced coconut palms and wartime construction. Restoration efforts led by The Nature Conservancy and the US Fish and Wildlife Service centre on Pisonia grandis, the birdcatcher tree favoured by nesting seabirds whose guano feeds both forest and reef, but a study in Current Biology involving Oxford researchers suggests the plan has been missing an ingredient: fungi.
In the first high-resolution survey of fungal diversity across the atoll, the team collected soil and root samples from 27 islets and analysed them with DNA sequencing, identifying 147 species of mycorrhizal fungi, the symbiotic networks that help plant roots capture water and nutrients. Comparisons with global databases suggest some species may be rare or entirely undescribed, and the fungi appear central to converting seabird guano and coral rubble into the moist peat in which trees can thrive.
Most striking was the specificity of the key relationship: across 52 sampled Pisonia trees, every root system was associated with the same fungal partner. For restoration science, the implication is that replanting trees without their symbionts may fail, and that managing the underground network is as important as managing what grows above it, a lesson with resonance for degraded island ecosystems worldwide.