// ARS TECHNICA — MONDO
Rewilding could help vulnerable islands keep pace with rising seas
Seabirds, native plants, and healthy reefs can help atolls build as seas rise.
Coral-fringed tropical atolls are among the landforms most threatened by global warming, but many have a potential superpower: Healthy ecosystems may help them keep pace with rising seas.
Atoll islands with native vegetation and thriving seabird populations are “naturally active systems that can change and adapt to their environmental conditions if they are allowed to do so,” said Nick Graham, a marine ecologist at Lancaster University in the United Kingdom, who led an international team of scientists that studied island resilience across 28 atoll islands in the Pacific and Indian oceans.
Their paper, published Wednesday in Science Advances, shows that restoring atoll ecosystems reinforces their growth. Seabirds ferry nutrients from the open ocean and deposit them on the atolls as guano that nurtures land plants, marine life and coral growth. This provides more material for reef building, as parrotfish and other reef feeders turn dead coral into sand to maintain beaches, while native plants with extensive root networks stabilize sediments.
Eradicating rats and replacing coconut plantations with native forests and brush could give some atolls a “fighting chance” to persist at the rate of sea-level rise expected toward the end of the century with about 2° Celsius (3.6° Fahrenheit) of warming, Graham said.
The findings provide more evidence that nature restoration can buffer the impacts of global warming. For example, restoring wetlands and forests dampens swings between wet and dry spells, reducing flood and fire hazards. Restoration efforts can also slow global warming by supporting natural carbon storage.
On the 28 atoll islands Graham’s team studied, strengthening the dynamic system of seabirds, native vegetation, and reef systems starts a virtuous cycle, as ecosystems become 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. Graham said terrestrial ecologists, marine ecologists and geomorphologists combined measurements of seabird populations, native vegetation, and coral and reef organisms to trace how energy moves through the ecosystems.
The scientific approach, called ecosystem energetics, uses energy flow as a common currency to connect organisms typically studied in isolation.
Seabirds link the open ocean, where they feed, to the land, where they nest. Thousands of birds swarm out across vast seas, and the food they digest is concentrated into a nutrient-rich guano. Islands with greater seabird nutrient input tended to have more productive coral communities and a higher energy flow.