We are facing a triple planetary crisis – which comprises the adverse impacts of climate change, nature and biodiversity loss and pollution.

Threats to coastal cities

Globally, approximately 1 billion people are projected to be at risk from coastal-specific climate hazards.

This is increasing, with predictions that by 2025, nearly 6 billion people will live within 200km of a coastline. The 2021 IPCC Special Report on the Ocean and Cryosphere in a Changing Climate underscores how human activity is changing the ocean faster than at any point over the past 65 million years.

2019 was declared as the warmest ever for the ocean and 2022 marked the second-lowest extent of Arctic sea ice since satellite records began. Ocean heating from CO₂ emissions results in a rise in sea levels, intensifying storms and damage to marine ecosystems that provide essential services including their protective benefits, food security and climate regulation. Changes to the ocean pose threats to the lives and livelihoods of billions of people, most of them in the poorest and most vulnerable communities in the Global South and in Small Island Developing States (SIDS), with women and girls experiencing particularly severe impacts.

Crucial strategies for adaptation include infrastructure construction and maintenance, beach nourishment, and diversification away from activities vulnerable to climate change. If governments undertake some of these strategies, the projected population exposed to flooding could be halved by 2100. Without adaptation, the annual costs related to flooding alone could range between $5 billion and $9 billion.

Challenges for coastal cities

With a tenth of the world’s population and physical assets at less than 10m above sea level, coastal cities are disproportionately affected by sea level rise, and other climate-compounding climate- and ocean-driven impacts.

With a tenth of the world’s population and physical assets at less than 10m above sea level, coastal cities are disproportionately affected by sea level rise, and other climate-compounding climate- and ocean-driven impacts.

Coastal cities are where the greatest number of people, very high levels of investment in built infrastructure, and perhaps the most ecological resources are in danger from global climate change.

Not only do climate change impacts such as sea level rise, storm surges and increasing temperatures adversely impact coastal ecosystems, but these climate risks also compound existing pressures such as threats to development and health. In addition, in many cities around the globe, rapid urbanization is outpacing infrastructure development – including housing and waste management – adding to the vulnerability of coastal cities.

While coastal cities are vulnerable to climate change impacts, these hubs have also been identified by the IPCC as central to climate change adaptation and mitigation action. As a result of the recognition of their increased vulnerability, and exposure to interconnected and multi-dimensional risks, many cities, towns and regions have developed adaptation plans and/or holistic resilience strategies. 

However, the follow through of these plans has been uneven around the world’s coastal areas. Some cities and regions have only been able to implement a few elements of these plans because of capacity and resource constraints, which has led to urban adaptation gaps across regions in coastal areas and for all current and future hazards. To address this problem, this Community of Practice is aimed at facilitating an increase in implementation of commitments and planning to ensure cities take action towards building their resilience.

Cities are taking action

A growing number of cities are stepping up to the challenge of climate change, relying on their deep stores of knowledge and expertise. For centuries, cities and states bordering ocean and waterways have had to contend with local sea-level fluctuations and periodic storms, experimenting with a combination of adaptation measures. However, these measures might not be appropriate for future changes, particularly given the rate of urbanization and because climate-related events are happening more frequently than in the past, in some cases overwhelming local capacities to respond.

A growing number of coastal cities are making massive investments in technical solutions to improve their climate resilience. Large infrastructure schemes, including barriers and break-walls, can at least temporarily reduce the risks of losses – but an overreliance on concrete walls and pump systems to beat back rising tides, storm surges and downstream floods has its limitations. As a result, many cities are turning to nature-based solutions to strengthen their climate resilience.

Want to know more about what your city can do?
On the UN Convention on Biodiversity-recognized CitiesWithNature Action Platform, your city can make commitments, take action and track your progress as you work towards your goals!

Nature-based solutions

Nature-based solutions (NbS) provided by coastal ecosystems (such as mangroves, tidal marshes, coral reefs, sand dunes, seagrass beds and seaweed) hold great potential for both mitigation and adaptation to climate change. As per IUCN definition, NbS are actions to protect, sustainably manage and restore natural or modified ecosystems that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits.

There is growing awareness that NbS can help to protect us from climate change impacts while slowing further warming, supporting biodiversity and securing ecosystem services. The potential of NbS to provide the intended benefits is still being rigorously assessed to address concerns about their reliability and cost-effectiveness compared to engineered alternatives, and their resilience to climate change. If climate mitigation policies encourage NbS with low biodiversity value – such as afforestation with non-native monocultures – maladaptation can occur, especially in a rapidly changing world where biodiversity-based resilience and multi-functional landscapes are key.

Want to know more about nature-based solutions?
Explore a list of resources from our range of partners by using the tag filter!

Future challenges

For climate change adaptation, key innovations in social policy and NbS with safeguards have not been matched by innovation in adaptation finance. Finance has tended to exclude the poorest communities, favor large-scale engineering projects rather than maintenance or social innovations, and prioritize gray/physical solutions over NbS, reproducing the risk of stranded assets, and maladaptation.

It’s against this backdrop that this Community of Practice offers coastal cities a space to share resources, experiences and best practices to build coastal resilience. Accordingly, this Community of Practice aims to contribute to some of the remaining gaps in climate change adaptation identified by the IPCC.

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