Project status
Marine and Freshwater
Contact details

By 2050 plastic in the ocean may outweigh fish if nothing changes. We need to tackle the plastic pollution problem together by going #OneLess. 

A fish with a plastic bottle in the ocean

What is the ocean plastic problem?

The ocean supports all life on Earth and its health is inseparable from our own. It provides us with half the oxygen we breathe, supports the livelihoods of billions of people worldwide, and is home to nearly 200,000 identified species. Yet, it is currently under threat – from plastic pollution. 

Experts estimate that up to 14 million tonnes of plastic enter the ocean each year. Plastic pollution demonstrates how inextricably linked the ocean and climate are - if the ocean can't function, its role in the climate system is compromised. Both crises must be tackled together. And we all need to play our part. 

Old plastic bottles on a beach

How are we working to reduce plastic pollution in our oceans?

The #OneLess campaign was established in 2016 by the Marine CoLABoration as an experiment to turn the tide against single-use plastic within a complex urban setting.

Led by ZSL, in collaboration with Forum for the Future, the International Programme on the State of the Ocean, and the Thames Estuary Partnership, #OneLess worked with businesses, policymakers, innovators and communities to spearhead a change in the way Londoners drink water – from single-use plastic water bottles, to refilling and reusing.

#OneLess is now a wider network achieving positive action every day. It will continue to grow in different ways as pioneering organisations spread their learnings and new approaches evolve for different parts of the globe. 

In six years, the #OneLess campaign eliminated 9 million single-use plastic items.
Read more about our campaigns, scientific research projects and wider impact.

What has the #OneLess campaign achieved?

In six years, #OneLess eliminated 9 million single-use plastic items; dispensed 981,000 refills from new drinking fountains; and removed 137,000 bottles from the River Thames in partnership with Thames21 and citizen scientists.

After catalysing significant change across the hydration system in London, the experimental phase of #OneLess came to a close in January 2022. To ensure the movement continues to grow in years to come, the #OneLess team created a Roadmap for London, which identifies exciting and achievable opportunities for everyone to further eliminate plastic bottled water in the city. 

We also developed a Practical Guide to using systems change approaches to tackle an environmental conservation issue. This is a free, open-source guide, available to anyone with an interest in replicating and scaling the #OneLess approach in other cities around the world. When we join together, everything is possible. 

People involved at ZSL

Heather Koldewey, Fiona Llewellyn, Shauna Jordan, Surshti Patel and Alice Chamberlain.



Help us protect our oceans

Go #OneLess today - because everything we do touches the ocean 


  • The Selfridges window display for Project Ocean which reads No More Fish in the Sea?
    Help us protect our oceans

    Project Ocean

    By 2025 there will be one tonne of plastic for every three tonnes of fish in the world’s oceans if nothing changes.

  • A group of citizen scientist volunteers in a river
    Support our Thames conservation work

    Thames Conservation

    The river Thames is not only a busy urban waterway but is also home to a fascinating and often unexpected array of wildlife.

  • Ducie sharks swimming in the ocean above coral
    We're protecting marine habitats of UK Overseas Territories

    Great British Oceans

  • freshwater lake
    Our work across the globe

    Habitats and Regions

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