New research from an international team of scientists working on Palmyra Atoll reveals that some of the most important recovery in island restoration happens underground. Specialized fungi living around tree roots are a critical part of the ecological network that allows one of the Pacific’s most spectacular native forest ecosystems to thrive. 

For those of us at Island Conservation, the findings are especially exciting. In 2011, we worked with partners to restore Palmyra’s native Pisonia grandis forests, helping drive an extraordinary increase in natural regeneration and forest recovery. Within five years, Pisonia growthh increased by more than 5,000%, setting the stage for the return of a thriving, interconnected ecosystem. 

Now, the ecosystem is giving something back: new scientific insights that are helping researchers understand how tropical island forests function and how they can be restored around the world. 

The Power of Connector Species

One of the clearest lessons from Palmyra is that healthy ecosystems are built on relationships. 

At the center of this story are seabirds, which act as a classic “connector species.” They spend much of their lives feeding far out at sea, then return to islands to nest and roost. In doing so, they transport nutrients from the ocean onto land through their guano, creating one of nature’s most powerful nutrient-delivery systems. 

These nutrients, including Nitrogen, Phosphorus, and Potassium, help fuel the growth of island forests, boost the health of coral reefs, and support entire ecological communities. 

Pisonia trees and seabirds have evolved a particularly close relationship. Seabirds prefer nesting in Pisonia forests, while the nutrient inputs from those birds help create conditions that support robust forest growth. On tropical atolls where soils are often thin, sandy, and nutrient-poor, this partnership becomes especially important. 

The Missing Piece Was Underground

Scientists have long recognized the connection between seabirds and Pisonia forests. What remained unclear was how those nutrients were transformed into forms that trees could actually use. 

The new study provides a compelling answer: mycorrhizal fungi. 

These fungi live in association with plant roots, forming underground networks that help plants acquire nutrients and water. Researchers surveyed soils and roots across 27 islets of Palmyra and used DNA sequencing techniques to create the first high-resolution map of the atoll’s fungal diversity. 

Key findings included: 

• Identification of 147 species of mycorrhizal fungi across the atoll. 

• Evidence that some fungal species may be rare or previously undescribed. 

• Discovery that Pisonia trees consistently associate with fungi from the genus Tomentella. 

• Findings that one species, Tomentella pisoniae, appeared in nearly every sampled Pisonia tree. 

Researchers found that 100% of the sampled Pisonia roots were associated with Tomentella fungi, suggesting an unusually specialized partnership. Most trees work with many different fungal partners; Pisonia appears to depend heavily on one. 

From Seabird Nutrients to Rainforest Soil

The research suggests these fungi serve as a critical bridge between seabirds and forests. 

Palmyra’s Tomentella fungi appear uniquely adapted to soils enriched by large quantities of seabird nutrients. Scientists found these fungi thriving in soils with extremely high phosphorus levels, indicating they may play an important role in recycling nutrients and making them available to trees. 

In effect, the ecosystem functions as a living partnership: 

• Seabirds bring nutrients from the ocean. 

• Fungi process and recycle those nutrients underground. 

• Pisonia trees capture those nutrients for growth. 

• Expanding forests provide habitat for more seabirds. 

The result is a powerful positive feedback loop that supports both terrestrial and marine ecosystems.

Another Unexpected Partner: Crabs

The study also highlights the role of land crabs as ecosystem engineers. 

Researchers found that crab burrows contained significantly greater fungal diversity than surrounding soils. By digging, mixing, and aerating the ground, crabs may help distribute fungal spores and create conditions that support healthy soil communities. 

This finding reinforces another important restoration lesson: 

Healthy ecosystems depend on interactions, not isolated species. 

Seabirds, trees, fungi, crabs, soils, and coral reefs are all connected through a web of relationships that has developed over thousands of years. 

Why This Matters Beyond Palmyra

The implications extend far beyond a single Pacific atoll. 

As restoration practitioners work to recover island ecosystems around the world, the study suggests that attention must be paid not only to plants and animals, but also to the microbial communities that support them. Researchers even suggest that future restoration projects may benefit from introducing beneficial soil fungi alongside native tree seedlings. 

Palmyra Atoll shows that when ecological connections are restored, ecosystems can recover in remarkable ways. And as they recover, they continue to teach us new lessons about resilience, cooperation, and the extraordinary complexity of the natural world. 

FAQ

What did the new Palmyra Atoll study discover?

Specialized mycorrhizal fungi, particularly Tomentella pisoniae, play a crucial role in helping Pisonia forests access and recycle nutrients delivered by seabirds. 

Why are seabirds so important?

Seabirds transport nutrients from the ocean onto islands through their guano, enriching soils and supporting forest growth. Scientists describe them as critical connectors between marine and terrestrial ecosystems. 

What are mycorrhizal fungi?

Mycorrhizal fungi form symbiotic partnerships with plant roots, helping plants acquire water and nutrients while receiving carbon from the plants in return. 

Why is Pisonia grandis important?

Pisonia forests provide high-quality nesting habitat for many seabird species and help drive nutrient cycling that benefits entire island ecosystems, including their surrounding waters. 

What role has Island Conservation played on Palmyra?

Island Conservation and its partners have worked for years to support the recovery of Palmyra’s native ecosystem, helping create conditions that led to dramatic Pisonia forest expansion, including more than a 5,000% increase in regeneration and growth in some areas. 

Why does fungus research matter for restoration worldwide?

The study highlights that restoring ecosystems means restoring relationships. Successful restoration may depend not only on recovering plants and animals, but also on rebuilding the microbial partnerships that allow ecosystems to function and thrive.