Palmyra’s returning forest also needs its fungal partners

Restoration reaches below the roots

Published online on 28 April 2026 in Current Biology, a study adds an underground dimension to forest restoration on Palmyra Atoll. Charlie Cornwallis and colleagues mapped mycorrhizal fungi and their relationship with Pisonia grandis trees. They found a particularly close partnership with fungi in the genus Tomentella. The availability of these partners may affect whether native forest regeneration succeeds. Read the original paper.

Palmyra lies in the Pacific’s Northern Line Islands. Pisonia trees provide nesting sites for seabirds, whose guano delivers substantial nutrient inputs to land. The researchers investigated fungi that can operate in this unusual environment while associating with tree roots. Plants, birds and soil organisms are connected through nutrient cycling, making the distribution of a small underground partner relevant to a much more visible forest.

A map of a specific partnership

The work examined roots and soils from 27 islets. As the University of Oxford announcement explains, Tomentella occurred in every sampled Pisonia root system, with one species present in almost every sample. This does not resemble a simple arrangement in which any tree can use any fungus available in the soil.

Tomentella also occurred across different atoll habitats, but its abundance was related to distance from Pisonia. Soil conditions mattered, including strong nutrient enrichment associated with seabird guano. The authors additionally found an association between crab burrows and higher fungal diversity. That relationship suggests mechanisms worth testing, but does not by itself establish that burrowing causes the entire observed difference.

Some detected fungi were rare in global databases or poorly documented. A sequence’s rarity in a database does not automatically demonstrate that its organism occurs nowhere outside Palmyra. Formally describing a new species requires separate taxonomic work. The central contribution here is the distribution map and the evidence connecting fungal partners with their hosts and environment.

What this adds to forest recovery

Restoration has a longer history. SPUN’s account describes rat eradication in 2011 and efforts to reduce coconut palm dominance as steps that created opportunities for regeneration. The 2011 USGS management plan already treated monitoring and research as parts of management that should change as evidence accumulates. That historical document helps place the current fungal findings within an ongoing process of understanding and improving habitat recovery.

The new map can guide researchers towards native fungal partners for regenerating trees. Directly testing whether inoculating seedlings improves survival remains a further research step. Proposed microbiome transplants should not be described as an already successful restoration experiment. Palmyra instead illustrates why rebuilding a habitat requires attention to organisms that remain invisible when surveying tree canopies. Measuring those hidden relationships can change which questions managers ask, what they monitor and how they design the next test of a restoration method.