From rising seas to resilient cities, the 3rd United Nations Ocean Conference (UNOC3), held from 9 to 13 June 2025 in Nice, France, made one thing clear: the future of our ocean will be shaped not only by global declarations, but by the determined leadership of cities and regions already navigating the tides of change.
Bringing together over 175 countries, dozens of international organisations, and more than 10,000 participants, UNOC3 was billed as a pivotal moment for ocean governance and climate ambition. Across the bustling Blue Zone and coastal venues, ocean champions rallied for urgent, tangible measures to protect marine biodiversity, unlock sustainable finance, and strengthen communities on the frontlines.
Local governments leading the charge on sea level rise
Sea level rise emerged as a defining issue throughout the Conference, both in formal declarations and in the powerful testimonies of coastal leaders. While the “Our Ocean, Our Future” Declaration acknowledged the urgency of rising seas, many noted it fell short of fully recognising the central role of local governments in driving adaptation where it matters most: in communities at risk.
That gap was addressed head-on at the Ocean Rise & Coastal Resilience Summit, a landmark moment held on 7 June in Nice. Co-hosted by the Governments of France and Costa Rica and the City of Nice, and supported by the Ocean & Climate Platform and the Global Centre for Climate Mobility (GCCM), the Summit brought together more than 200 mayors, governors, and subnational leaders from around the world.
Real change happens from the ground up. Communities are not just victims of this crisis, they are the drivers of solutions.
— Héctor Mendoza, Mayor of Trujillo, Honduras
The Summit marked the official launch of the Ocean Rise and Coastal Resilience Coalition, a new global mechanism to accelerate sea level rise adaptation by fostering deep cooperation between local governments, scientific institutions, civil society, and finance actors. The Coalition will be hosted by the GCCM under UNOPS.
ICLEI – Local Governments for Sustainability is a core partner of the Coalition. ICLEI co-organised and facilitated two of the Summit’s high-level sessions and supported the Coalition’s architecture, helping to ensure that the voices of cities and regions were not only heard, but central to shaping global coastal resilience strategies.
The interaction between land and sea is in constant flux, and this dynamic directly affects the communities living along our coasts. Sea levels will continue to rise under all emissions scenarios. In the face of this, I offer three key pieces of advice:
1. Deepen cooperation, sea level rise demands collaboration across sectors and borders.
2. Recognise that sea level rise is fundamentally a local issue, support local governments.
3. Harness local knowledge, listen, invest, and scale what works.
— Peter Thomson, UN Secretary-General’s Special Envoy for the Ocean
Significant announcements followed. The French Space Agency launched the Space4Ocean Alliance, inviting local governments to co-design space-based resilience tools. The European Commission unveiled €45 million in new Horizon funding for coastal cities and islands.
Linking ocean action with the nature agenda
The energy at UNOC3 wasn’t limited to climate adaptation. It also catalysed alignment between ocean protection and global biodiversity goals, particularly the 30×30 target to conserve 30% of the ocean and land by 2030. Coastal ecosystems, such as mangroves, salt marshes, and tidal flats, were repeatedly highlighted for their dual role in protecting shorelines and nurturing biodiversity.
ICLEI spotlighted this nature–climate–ocean nexus across multiple engagements, including sessions on port cities and the blue economy, and localising SDG 14. During the World Coastal Forum side event, ICLEI’s Deputy Secretary General Kobie Brand reaffirmed the need to embed coastal nature into urban planning and investment decisions, stating:
You cannot achieve 30×30 without coastal cities on board, they are where biodiversity, climate, and development collide.
ICLEI also joined partners including UN-Habitat, the Ocean & Climate Platform, and the Government of the Netherlands to showcase how nature-based solutions, traditional knowledge, and multilevel governance can unlock coastal resilience, especially in Small Island Developing States (SIDS) and rapidly urbanising coastlines.
Our cities are not only on the frontline of climate impacts, they are also on the frontline of solutions.
— H.E. Ralph Regenvanu, Minister for Climate Change, Energy and Environment, Vanuatu
Cities will carry the momentum forward to COP30
As the global community now turns its attention to COP30 in Belém, Brazil, the messages from Nice are resoundingly clear: local governments must be seen as co-leaders in the ocean–climate–nature space, not as passive implementers. The path to a healthy, just, and resilient ocean depends on empowered coastal cities, resourced to act, equipped to innovate, and backed by strong partnerships.
ICLEI will carry this momentum forward, working with allies across science, finance, and civil society to scale solutions from the coast up, helping cities and regions build a thriving ocean future for all.
