For centuries, indigenous islanders have understood that land and sea are connected. As we come up with strategies to protect and heal our planet’s oceans, this wisdom implores us to consider the ecosystems that impact the oceans—and islands are at the top of the list. 

Because of their singular geographic qualities—separate from other land—terrestrial island ecosystems harbor some of the most amazing biodiversity and unique species in the world. Plants and animals found on islands can often be found nowhere else in the world.  

But protecting islands and improving the health of their ecosystems has multiple benefits that go beyond saving species. A healthy island can support food security and wellbeing for local communities, capture carbon and resist the effects of climate change, and safeguard precious natural and cultural resources. And thanks to a growing network of global partnerships, island restoration is now understood as a vector for restoring and strengthening our planet’s oceans, too. 

Connector Species and Nutrient Recycling 

Seabirds, sea turtles, and seals are connector species that play a vital role in maintaining the health of ocean and island ecosystems by transporting essential nutrients between land and sea. Among these, seabirds are especially important due to their nutrient-rich guano, which contains high levels of nitrogen—a key element for plant and animal growth. This guano not only fertilizes island soils, promoting lush vegetation, but also supports coral reef ecosystems by nourishing macroalgae and reef organisms.  

The 2018 study “Seabirds Enhance Coral Reef Productivity and Functioning in the Absence of Invasive Rats” reveals that restored islands have seabird densities 760 times higher and nitrogen deposition rates 251 times higher than islands where harmful, invasive species interrupt nutrient flows. The higher nitrogen values in restored islands also appear in macroalgae, filter-feeding sponges, turf algae, and fish on adjacent coral reefs. Herbivorous damselfish on reefs adjacent to healthy islands grow faster, and fish communities have 48% greater overall biomass across trophic feeding groups. Additionally, rates of grazing and bioerosion are 3.2 and 3.8 times higher, respectively. Ecosystem functions such as grazing and bioerosion are crucial because they help maintain the balance and health of coral reefs by controlling algae growth and breaking down substrates, which supports coral regeneration and overall reef resilience. This one intervention—the restoration of an island—has cascading benefits that positively influence the entire island-ocean ecosystem.

Coral Reef Health 

In 2024, restoration in the Chagos Archipelago provided an excellent case study that proved how island restoration could support coral reefs. The study “Island Restoration to Rebuild Seabird Populations and Amplify Coral Reef Functioning” found that restoring seabird populations on islands in the Chagos Archipelago could increase breeding pairs to over 280,000. This restoration would lead to significant nutrient flows from seabird guano, enhancing coral growth rates and reef fish biomass. When these nutrients enter the marine environment, they enhance the productivity of coral reefs by promoting the growth of algae and other microorganisms that corals rely on for food. Specifically, coral growth rates could increase by 90%, and reef fish biomass could see a 52% boost. Additionally, parrotfish grazing and bioerosion rates, crucial for maintaining healthy coral reefs, could increase by 140% and 270%, respectively. These findings underscore the importance of seabird-driven nutrient cycling in supporting resilient and productive coral reef ecosystems. 

The Island-Ocean Connection Challenge 

In 2022, Island Conservation, Scripps Institution of Oceanography at UC San Diego, and Re:wild came together to create the Island-Ocean Connection Challenge (IOCC). We launched this initiative to learn from and partner with indigenous peoples and local communities, whose wisdom bridges the gap between island, coastal, and marine ecosystem management, recognizing the profound link between terrestrial and ocean restoration. 

By collaborating with island communities, their governments, NGOs, scientists, and funders, we aim to begin holistically restoring 40 globally significant island-ocean ecosystems from ridge-to-reef by 2030. 

On Loosiep Island in the Federated States of Micronesia, restoration interventions improved traditional agriculture practices, reducing reliance on imported food. And in French Polynesia, the Critically Endangered Polynesian Storm-petrel has returned to nest on Kamaka Island for the first time in 100 years—less than two years after ecosystem restoration efforts began. 

Connection is the Answer 

Understanding that land and sea are connected is an essential part of the future of ocean advocacy. Centering islands, and the wisdom of people who live on them, can galvanize not just ridge-to-reef ecosystems but also new partnerships. The time of strict separation between terrestrial restoration and marine conservation is over: it’s time to build a healthier planet by bringing these areas of focus together. 

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