The ocean covers more than 70 per cent of the planet and regulates climate, sustains biodiversity, and supports economies and cultures worldwide. It's the foundation of life on Earth.
However, it has been under duress for some time and going forward faces multiple threats which not only gravely endanger its future health but the future of humanity itself.
Some 550 experts from 86 countries have spent almost five years compiling a 1600-page assessment detailing the challenges the ocean faces. This scientific guide delivers the knowledge humankind needs to protect and sustain the planet.
It's called the World Ocean Assessment, and here's what those 1600 pages reveal.
The ocean matters to everyone, everywhere
- The ocean shapes everyone's daily life even if they do not live in coastal zones.
- It stabilizes the climate by absorbing most of the planet's excess heat as well as damaging greenhouse gases. Without its cooling effect, more extreme weather can be expected which will threaten food systems and supply chains, and insurance markets.
- It serves as food supply. When fish stocks collapse or supply chains break due to climate impacts or illegal fishing, prices rise, not just for seafood, but for many foods that rely on global trade and coastal economies.
- It provides mental and physical health benefits, medicines, and a significant share of breathable oxygen.
- The ocean supports trillions of dollars in global trade, tourism, and jobs.
The ocean is under intensifying stress
Humans are reshaping marine ecosystems. The global population reached 8.2 billion in 2024, with 37 per cent of those people living within 100 km of the coast.
Inevitably, this has concentrated human and economic activity in vulnerable coastal zones, increasing the extraction of natural resources, infrastructure expansion, waste discharge, and habitat degradation.
At the same time, offshore development is intensifying, with wind farms, deepwater oil infrastructure, and expanding seabed cables and pipelines altering habitats farther from shore.
Climate change is transforming conditions
Data relating to ocean warming and sea level rise is dramatic.
- The rate of sea level rise, due to melting ice caps and temperature-driven water expansion, has doubled from up to1.9 mm/year before 2015 to 4.3 mm/year in 2023.
- Arctic temperatures are rising four times faster than the global average.
- Hypoxic (or dead) zones, where oxygen levels are so low that most marine life cannot survive, now span 4.5 million km².
- 16 per cent of the total increase in ocean temperatures since 1955 has occurred after 2018.
Biodiversity is declining across nearly every marine habitat
Marine life is under severe stress, reflected in the approximately 80 per cent decline in Caribbean coral reefs since the 1970s. Ninety per cent of global coral reefs may disappear if warming exceeds 1.5°C above industrial levels.
Critical coastal ecosystems, like mangroves and seagrass, continue to shrink.
Species from plankton to marine mammals are shifting towards the North and South Poles as temperatures rise, while non-indigenous species are spreading more easily under altered environmental conditions.
Pollution is widespread and increasing
Marine pollution is intensifying.
Each year, 52 million tonnes of plastic waste enter the ocean, contributing to an estimated 24 trillion microplastic particles, which are now known to affect more than 4,000 marine species.
Chemical contamination is also rising, with over 4,000 pharmaceutical and personal care compounds detected in marine waters.
The good news? Some legacy pollutants such as mercury have declined in a few regions.
Ocean food systems are threatened
Marine food systems are a vital source of nutrition and livelihoods, providing 20 per cent of animal protein consumed by humans globally.
Marine aquaculture continues to expand and has become a global $90 billion industry. In addition, 121 million people engage in marine recreational fishing, contributing to local economies and well-being.
Yet the stability of these systems is increasingly at risk:
- 37 per cent of fish stocks were overfished in 2021.
- Illegal, unreported, and unregulated fishing removes an estimated 8-14 million tonnes annually, generating $9-17 billion in illicit revenue.
- Disease outbreaks, pollution, and climate stress continue to challenge the long-term sustainability of marine aquaculture and fisheries.
The ocean economy is large but not yet sustainable
The ocean economy is valued at $1.5 trillion per year and projected to exceed $3 trillion by 2030.
Coastal and marine tourism supports 174 million jobs.
Efforts are being made to understand the ongoing impacts and sustainability of offshore oil and gas production as well as shipping which transports over 80 per cent of world trade and contributes to global greenhouse gas emissions.
Governance and knowledge
International cooperation on ocean governance is gaining momentum, but the 57 global treaties relating to ocean protection is resulting in a fragmented approach.
Achieving a sustainable ocean economy requires equity and the prominent inclusion of the knowledge and traditional practices of indigenous communities. Without them ocean health, community wellbeing, and sustainable and equitable development will be more difficult to achieve.
Large gaps persist in ocean knowledge, with only 27 per cent of the seafloor mapped as of 2025, leaving deep sea ecosystems, biological processes, and cumulative impacts poorly understood.
Solutions abound
Despite mounting pressures, solutions exist, including nature-based approaches, emissions reduction, and expanded marine protection.
However, even the full restoration of ocean ecosystems would contribute only around two per cent of global climate mitigation targets, underscoring the need for systemic change.
The coming decade is decisive: without rapid, coordinated global action, ocean health will continue to decline, threatening climate stability, biodiversity resilience, food security, livelihoods and the wellbeing of billions.
