Reversal Could Help Vulnerable Islands Keep Pace With Rising Seas

Seabirds, native plants and healthy reefs can help build coral islands as seas rise.

Researchers inspect heat-resistant corals in Tatakoto, French Polynesia.

Tropical atolls are among the land forms most threatened by global warming, but many have a potential superpower: healthy ecosystems may help them keep pace with rising seas.

Nick Graham, a marine ecologist at Lancaster University in the UK, who led an international team of scientists, said atolls with native vegetation and thriving seabird populations "are active natural systems that can change with their environment, and if they're allowed to do so, they can change and adapt."

Their paper, published Wednesday in Science Advances, shows that restoring coral ecosystems boosts their growth. Seabirds carry nutrients from the open ocean and deposit them as guano on atolls, which nurtures land plants, marine life, and coral growth. This provides more material to build reefs as parrotfish and other reef feeders turn dead coral into sand to maintain beaches, while native plants with extensive root networks stabilize sediments.

Eradicating the rats and replacing coconut plantations with native forests and brush could give some atolls a "fighting chance" to keep up with the rate of sea-level rise at the end of the century. About 2 degrees Celsius (3.6 degrees Fahrenheit) of warming, Graham said.

These findings provide further evidence that restoring nature can curb the effects of global warming. For example, the restoration of wetlands and forests reduces the fluctuation between wet and dry periods and reduces the risk of floods and fires. Restoration efforts can reduce global warming by supporting natural carbon storage.

Across 28 atoll islands, Graham's team studied, strengthening the dynamic system of seabirds, native vegetation and reef systems initiates the cycle as ecosystems are better able to sustain themselves and build resilience to growing impacts.

The research included data from islands in the Seychelles and Chagos archipelagos in the Indian Ocean, and Tetiaroa, an atoll in French Polynesia in the Pacific Ocean. Terrestrial ecologists, marine ecologists and geomorphologists combined measurements of seabird populations, native vegetation and coral and reef organisms to track how energy moves through ecosystems, Graham said.

The scientific approach, called ecosystem energetics, uses energy flow as a common currency to connect organisms that are usually studied separately.

Seabirds link the open ocean, where they feed, to land, where they nest. Thousands of birds flock to the vast seas, and the food they digest is concentrated in a nutrient-rich guano. Islands with higher seabird nutrient inputs tend to have more productive coral communities and higher energy fluxes.

Parrotfish and other reef nibblers also contribute to the energy flow by scraping coral to feed on dead organisms and excreting sand-sized particles. Calcareous algae, other reef organisms, and shellfish help build up the reef framework and help the reefs protect the islands from waves.

In the terrestrial part of the cycle, the restoration of native vegetation, which is replaced by coconut plantations, is very important. Coconut palms have small and unstable roots that make the surrounding soil vulnerable to erosion. In contrast, native plants have massive networks of fine mesh roots that connect and stabilize the shallow, porous soil and also provide better habitat for seabirds.

Restoring the nutrient cycle also means eliminating invasive rats brought in by colonizers who have devastated seabird colonies for centuries. This cycle has maintained coral ecosystems since at least the end of the last ice age. A 2026 study of 288 reef core growth records found that most are consistent with sea level rise, although this capacity varies by location and is not guaranteed at current rates of warming.

The new study measures "reef aggregation potential" for islands, and shows that it is twice as high on ocean-facing, lagoonal reefs around rat-free islands with abundant seabirds than on rat-infested islands. "That's enough to keep up with projected sea-level rise by the end of the century under a 2°C warming scenario," said co-author Casey Benquit, a California-based restoration scientist, with The Nature Conservancy.

He added that reef growth rates without seabird populations are predicted to be lower as sea levels rise.

Graham cautioned that the study is not meant to be a panacea for the effects of global warming on low-lying islands. Direct comparisons before and after restoration were not made, and the data came from islands with different levels of seabird abundance and rat infestations, differences that the research team tried to address with an ecosystem energy framework.

And reef growth doesn't always mean an atoll grows vertically, as global warming also changes the waves, winds and currents that affect where the material ends up. The study also focused on mostly uninhabited or sparsely populated islands with room for native ecosystems. On developed atolls, he said, restoration efforts can help but not replace the need for engineering solutions.

Ecologist Hilary Young wrote in a Science Advances Focus commentary that the study helps show a nearly complete loop, "from ocean-foraging seabirds, through native forests and coral reefs, to the construction and stabilization of islands where the birds breed." Quantifying the ring, he wrote, "provides much-needed evidence that the fate of an atoll cannot be understood or managed by treating its land and sea separately."

Local protections can affect physical resilience to rising seas, but "rapid reductions in emissions continue to be necessary for the long-term viability of these systems," he wrote.

Bob Bruin is an Austria-based reporter who has covered climate science and international climate policy for more than a decade. He previously reported on the environment, endangered species and public lands for several Colorado newspapers and also worked as an editor and assistant editor for local newspapers in the Colorado Rockies.

This story originally appeared on Inside Climate News.