Changing climate, changing coasts: Why resilience matters

Coastal zones have always been one of the most attractive settlement areas because of their access to the ocean, their richness in natural resources, and the high quality of life they offer. As our new policy paper shows, today coastal zones are home to 2.4 billion people, or 40% of the world’s population, with a density three times higher than the global average. Many of the world’s largest cities lie along the coast, including Tokyo, New York and Mumbai.

Coastal zones are also global economic hubs: maritime transport is responsible for 80% of all goods traded globally, and a large share of global tourism flows depends on the coasts. In the United States, for example, 85% of tourism revenues are generated by coastal areas. Coastal zones also harbour some of the world’s richest ecosystems, such as mangroves and coral reefs, which sustain many economic activities and provide natural protection against natural hazards such as storm surges. At the same time, coastal ecosystems, such as mangroves, store up to five times more carbon (per km²) than mainland tropical forests, thus contributing to mitigate climate change.

Rapid socio-economic expansion has had harmful impacts on coastal ecosystems. Water pollution has altered the natural hydrological cycle and undermined ecosystems’ ability to regulate water flows and quality. The overexploitation of natural resources (e.g. sand and gravel) has contributed to rapid coastal degradation and erosion: globally, 25% of shorelines are eroding by half a metre annually and over half of coastal wetlands have been lost since 1990. Coastal groundwater extraction has also facilitated land subsidence, threatening low-lying agglomerations such as Bangkok and New Orleans. In addition, today, over 90% of waste entering the sea remains near the shore. While coastal ecosystem degradation harms coastal communities most directly, global economic activities that depend on the coast are equally at risk.

The high concentration of people, assets, economic activities and ecosystems along the world’s coasts makes them some of the most exposed regions to the impacts of climate change. And while all countries along the sea are set to experience the damaging impacts of climate change, low-lying areas such as river deltas, coastal plains and small island states will be particularly affected. Climate change affects coastal zones in multiple ways:

• The rise in global mean sea level is the most important consequence of climate change for low-lying coastal zones. Without adaptation, sea-level rise-induced floods are projected to affect 360 million people and generate USD 50 trillion in annual losses by the end of the century – equivalent to 4% of global GDP. Sea-level rise is not uniform across regions due to geological processes: for example, it is expected to rise three times faster than the global average in the western Pacific.
• Storms are another growing challenge affecting coastal zones. In the past 20 years, they have killed over 200 thousand people and generated economic losses of USD 1.4 trillion. Population in cyclone-prone areas is increasing more than twice as fast as the global average and, although uncertainty in storm projections is still high, climate models suggest that climate change may render coastal storms more intense in some regions. This is likely to increase episodic coastal flooding and accelerate coastal erosion, facilitating saltwater intrusion into freshwater aquifers and further contributing to the degradation of coastal ecosystems.
• Adding to the impacts of sea level rise and storm surges, the warming and acidification of coastal waters have negative impacts on coral reefs, fisheries and shallow water ecosystems. As these ecosystems provide many socio-economic benefits and reduce coastal vulnerability to natural hazards, their degradation is likely to have long-lasting effects on the overall resilience of coastal communities.

To respond to the growing and interlinked challenges of climate change and ecosystem degradation along the coast urgent policy is action is needed:

• Coastal management policies and strategies need to take the projected impacts of climate change into account. Knowledge of how climate change may alter ecosystems and livelihoods in the future is key for policy makers to identify and prioritise the right adaptation measures.
• Climate change adaptation needs to be integrated with other coastal zone management policies. These include policies that promote economic development (e.g. tourism and marine transport), land use planning (e.g. taking into account ecosystem functions and preservation), or measures that regulate agriculture and natural resource extraction (e.g. to avoid harmful impacts).
• Policy planning and regulatory development need to be co-ordinated across different sectors and levels of government and to involve non-governmental stakeholders such as local communities and private infrastructure operators. This will allow policy makers to identify synergies and trade-offs across different objectives and to find ways to balance stakeholder interests.

Through the work of the Task Force on Climate Change Adaptation, the OECD will continue to examine the issue of climate risks in coastal zones and how adaptation policies can best address them in the future.

For more information, please visit our website: https://www.oecd.org/environment/cc/climate-adaptation/

• OECD (2021), “Adapting to a Changing Climate in the Management of Coastal Zones”, OECD Environment Policy Papers, No. 24, OECD Publishing, Paris, https://doi.org/10.1787/b21083c5-en.
• OECD (2019), Responding to Rising Seas: OECD Country Approaches to Tackling Coastal Risks, OECD Publishing, Paris, https://doi.org/10.1787/9789264312487-en.