Invasive palms and WWII damaged an island paradise. Could fungi help to restore it?

Legions of seabirds squawked overhead as Toby Kiers bent down and grabbed a fistful of dark crumbly soil. She squeezed it between her fingers and brought some to her nose. “It smells really fresh. Vegetal, like vegetables. Like carrots or celery,” she said with a quick smile.

Kiers, an evolutionary biologist at the Free University of Amsterdam in the Netherlands, had travelled around the globe to hunt for fungi on the North Pacific atoll of Palmyra, one of the most remote islands on the planet. She was looking at tree roots to find symbiotic microorganisms called mycorrhizae, which form networks of filaments that help plants to absorb nutrients and water from the soil. They might also be a key part of the process that breaks down coral rubble on land into the peaty soil she found in some locations on Palmyra.

Kiers has sampled soil microbes worldwide, but her trip to Palmyra in November 2022 was the first time she had taken her search to an island. She is one of several researchers exploring whether below-ground microorganisms such as mycorrhizae could be a key to restoring heavily degraded ecosystems on these and other islands.

Palmyra’s 42 low-lying islets are home to some of the most pristine coral reefs in the world, but the above-water ecosystem has been radically altered — first by nineteenth-century coconut plantations that introduced invasive palm trees, and then by the US military, which dredged areas to create airstrips during the Second World War.

Now the atoll is uninhabited, except for a rotating cast of researchers testing how to repair degraded ecosystems. The non-profit global environmental organization The Nature Conservancy (TNC) bought Palmyra for US$30 million in 2000 and later sold part to the US government. The atoll is co-managed by TNC and the US Fish and Wildlife Service. The two organizations, along with Island Conservation, a California-based non-profit organization, have spent $4 million to eradicate rats in the past decade and are now in the middle of a $3.5-million effort to regenerate the atoll’s rainforest...