This article was originally shared by the Ocean Decade

Coastal cities are booming — over a third of the world’s population now lives within 100km of the sea. However, this expansion brings mounting challenges, from climate change-induced risks to human-driven environmental degradation. Ensuring these urban centers remain resilient while preserving marine ecosystems is a pressing global priority.

In this article, we highlight three initiatives endorsed by the UN Decade of Ocean Science for Sustainable Development 2021-2030 (‘Ocean Decade’) that are pioneering innovative solutions through science, technology, policy, and community action to shape the future of coastal cities.

Urban runoff, wastewater, and poorly planned development are reshaping coasts around the world — eroding wetlands, polluting seas, and contributing to ocean warming and acidification. As a result, only 15% of the world’s coastlines remain in their natural state.

From restoring urban seascapes to integrating marine protection into city planning, the three success stories below showcase how the Ocean Decade is harnessing science and knowledge to address these challenges, enhance the resilience of coastal cities to change, and improve the well-being of their inhabitants.

Reviving Sydney Harbour: Transforming urban seascape

For decades, Sydney Harbour has been at the crossroads of nature and urban expansion, where development and marine life struggle to coexist. The World Harbour Seascape Restoration Programme, led by the Sydney Institute of Marine Science, is working to restore this fractured marine ecosystem, proving that even in the most urbanized waters, marine life can make a comeback. Its Project Restore breaks away from traditional, one-habitat-at-a-time restoration to revive entire marine landscapes – bringing seagrasses, kelp forests, and reefs back to life as interconnected ecosystems.

In a historic first, 3,000 shoots of the endangered Posidonia australis seagrass have been carefully transplanted into Sydney Harbour, laying the foundation for lush underwater meadows. In parallel, 16 tonnes of sea urchins have been removed from two sites where rocky reefs once flourished to allow Ecklonia radiata kelp forests to reclaim their rightful space.

Project Restore Project Manager, Dr Francisco Martinez-Baena says, “we are closely monitoring the restoration sites, with results showing early success. Our Posidonia transplants are looking lush and healthy, with some starting to grow new shoots five months after being planted. On our rocky reefs, we see the first succession of macroalgae appearing, with juveniles of brown algae species such as Sargassum and Padina appearing.”

These efforts aim to develop a blueprint for seascape restoration in urbanized marine environments, a model that could be adapted globally to achieve large-scale improvements in urban harbors.

Predicting and preventing pollution in port areas in Quebec – and beyond

Let’s move from Sydney to Canada and visit the Port of Sept-Îles, Canada’s largest ore port, where artificial intelligence is playing a pivotal role in preventing pollution spikes. Nestled in an archipelago of seven islands, this natural hub ensures year-round ship anchorage, making it key to global trade while also exposing it to heightened environmental pressures from heavy maritime traffic, industrial activity, and coastal development.

Through the Enviro-Actions Project, led by the Northern Institute for Research in Environment and Occupational Health and Safety, autonomous scientific buoys (floating sensors) and monitoring stations are tracking critical water and air quality data in near real-time. But this technology doesn’t just collect data, it then acts on it: when pollution levels rise, preventive alerts are issued to halt further contamination.

“Enviro-Actions is using near-real time monitoring and artificial intelligence for the analysis of big-data and the transmission of preventive alerts to managers. With this system, we make a significant step forward in our ability to follow anthropogenic interactions with the environment and to design concrete measures to make marine-based industrial activities more sustainable.” - Julie Carrière, Ing. Ph. D., INREST Executive Director

The Project also measures underwater noise levels and analyzes long-term environmental trends to reveal the true impact of port operations. Enviro-Actions is not just a local initiative – it is currently being deployed to other coastal regions in Quebec such as at Saguenay, and it has the potential to be implemented in all industrial or port areas on the planet, setting a new standard for sustainable maritime operations.

Preparing for sea-level rise in coastal cities

Coastal communities are facing the alarming reality of sea-level rise, with some areas experiencing rates up to four times faster than the global average. Cities like Jakarta, Lagos, Houston, Rotterdam, and Venice could be submerged by the end of the century unless significant adaptive measures are taken.

Led by the Ocean & Climate Platform, the Sea’ties initiative is empowering coastal cities to tackle the challenges of sea-level rise head-on. It brought together over 280 stakeholders, from urban planners to scientists and elected officials, to create a global network focused on sharing challenges and leading practices of adaptation solutions.

This grassroot approach led the foundation to the international advocacy and mobilisation the project conducted. One key achievement of the initiative is the Sea’ties Declaration, which has rallied more than 70 mayors and city networks around four priority themes: mobilizing science and observation systems for adaptation; integrating societal issues with adaptation plans; fostering adaptive and hybrid solutions; and boosting public funding and private investments.

“We must act with foresight to make coastal urban areas resilient and adaptable, ensuring a sustainable and desirable future for their citizens. Uniting mayors and governors of coastal cities and regions alongside scientific institutions, the financial sector and civil society, the Ocean Rise & Coastal Resilience Coalition embodies our collective commitment to confront the crisis of sea-level rise head-on. Join us, the time is now!” - Loreley Picourt, Executive Director of the Ocean & Climate Platform

Given the expertise the Ocean & Climate Platform garnered through the Sea’ties project, it has been mandated by the President of France, Emmanuel Macron, to coordinate the preparation of the Ocean Rise & Coastal Resilience Coalition, chaired by the Mayor of Nice, Christian Estrosi. Launched at the 2025 United Nations Ocean Conference,  the Coalition will bring together a thousand cities and regions, representing 1 billion people worldwide confronted with sea level rise. Dedicated to supporting the adaptation and resilience of coastal cities and regions across the globe, this initiative will provide coastal cities with better access to knowledge, finance, and stronger international representation to ensure locally-led, long-term adaptation.

As we look ahead, opportunities to collaborate and innovate continue to grow. One such opportunity is the Ocean Decade International Coastal Cities Conference, happening on 26-27 February in Qingdao, China. This important event will bring together experts and stakeholders from around the world to address challenges and opportunities in generating and using ocean science for sustainable development. Be sure to follow the proceedings: watch the livestream.

For more information, please contact:
Ocean Decade Communications Team ([email protected])

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