Our Blue Planet: Defining Boundaries for a Thriving Ocean

10/03/2025

Covering more than 70% of our planet’s surface, the ocean plays a vital role for life on Earth. Its vast waters are home to everything from microscopic plankton to the world’s largest mammals. Billions find their food and livelihoods along its coasts and high seas. Roughly half the oxygen on Earth is generated by it and around a quarter of carbon dioxide emissions are absorbed into it.

Yet, the ocean is under threat. Pollution, climate change, and overfishing are taking a toll on marine ecosystems and people alike. At the same time, large areas of the ocean remain unstudied, leaving critical gaps in our understanding of its limits and resilience. Without clear scientific guidelines, we risk destabilizing the ocean’s ability to sustain life—including our own.

To address this, a new working group within the Earth Commission will define the first ever safe and just boundaries for the ocean. These boundaries set scientific thresholds on human activity to ensure the ocean remains healthy while balancing a stable planet with economic and social justice.

“We need to understand what constitutes a healthy ocean ecosystem,” said David Obura, one of two Commissioners co-leading the team of researchers. “Ocean biomes are far larger than those on land, and their health is fundamental to the overall functioning of the planet.”

A marine biologist who specializes in coral reefs, Obura said the group will begin identifying potential indicators—like fish biomass—that can serve as benchmarks to assess whether the ocean remains within safe ecological limits.

The team spans five continents and includes 15 researchers with expertise in areas like marine biology, agriculture, food systems, and social science. Its efforts are still in the early stages, reviewing the latest research.

Ocean biomes are far larger than those on land, and their health is fundamental to the overall functioning of the planet.

David Obura

Once the boundaries are set, the team will also explore what must be done for humanity to stay or return within them if they are breached. Its findings can then be used to inform science-based targets for businesses and governments.

A Safe and Just Ocean: Setting Critical Boundaries

The Earth Commission has already established boundaries for five key areas of the Earth system: land, freshwater, climate, air and nutrient pollution.

However, setting these boundaries also requires a scientific approach to justice. Co-lead Commissioner Rashid Sumaila, an economist specializing in ocean resources, emphasizes the need to balance conservation with human well-being. “It’s not just about keeping fish stocks healthy; it’s about ensuring that communities dependent on the ocean can thrive within these boundaries,” he said.

Unlike other scientific frameworks, the Earth Commission incorporates justice into all its assessments. This means defining limits in a way that prevents significant harm from happening to all species and people, including future generations, as well as ensuring that everyone on Earth has access to resources for a dignified life.

For the ocean, this could be ensuring vulnerable coastal communities have access to fisheries. It could also mean setting limits on pollution and overfishing in ways that protect both biodiversity and the rights of indigenous and small-scale fishers. By integrating justice, the Earth Commission aims to create boundaries that are not only scientifically sound but also socially equitable.

It’s not just about keeping fish stocks healthy; it’s about ensuring that communities dependent on the ocean can thrive within these boundaries

Rashid Sumaila

The Bigger Picture: Ocean Health and Global Systems

The ocean does not exist in isolation. What happens on land directly impacts its health. Agricultural runoff pollutes coastal waters, rising temperatures drive coral bleaching, and economic pressures fuel overfishing and habitat destruction. A key challenge for the Earth Commission team is addressing these interconnected threats holistically.

“We cannot set ocean boundaries in isolation,” Sumaila said. “They must be integrated into broader efforts to tackle climate change, economic inequality, and sustainable development.”

For Obura, this work will be a particular challenge. As a field ecologist who lives on the coast, he has seen firsthand the rapid decline of coral reefs and understands how their futures are interlinked with the wider world.

“Coral reefs and mangroves and seagrasses, they’re right at the boundary of land and sea,” he said. “They experience very complex sets of interactions. So it’d be very interesting to see how what we find for the ocean boundaries will have linkages with the ones we’ve already identified for the other systems.”