The Economic Implications of Rising Sea Levels for Coastal Cities & Adaptation Strategies
Ella Lindsay and Emma Chretien
Introduction
This commentary will discuss the costs coastal cities face because of sea level rise and how adaptation or mitigation might help.
Economic Impact of Rising Sea Levels
Sea levels increase because glaciers and polar ice caps are melting due to rising global temperatures. Both economies and coastal infrastructure are at risk. “During the 20th century, a significant acceleration of sea-level rise has occurred, quantified at about 1.2 mm per year from 1901 to 1990… the period 1993–2010 revealed a much larger acceleration, of about three millimeters per year” (Abadie et al., 2020). The economic impact of sea-level rise on coastal cities is multifaceted.
Firstly, the rising sea levels cause direct damage to buildings, roads, and utilities. Ralls (2024) reports, “a recent study has unveiled alarming projections for world economies, with estimated losses reaching well over $1 trillion by the century’s end due to the impact of rising sea levels on coastal cities”. Roads, bridges, and ports are the costliest repairs at risk from rising sea levels; these areas of infrastructure make up the majority of the estimated $1 trillion spent by the end of the century (Ralls, 2024).
Aside from the cost to repair infrastructure, there are also the costs associated with long-term economic consequences. It is common that coastal cities, especially in North America, have large amounts of tourism that contribute significantly to the national GDP. Additional costs come from adapting these coastal cities to protect them from sea level rise, such as building seawalls and updating drainage systems. In Europe, nearly 30% of the population “resides in a 50 km strip of the coast, where many ecosystems, assets and infrastructures are located” (Abadie et al., 2020), which proves to be problematic for these coastal cities as rising sea levels has been a growing concern due to socioeconomic factors in the past, climate change is expected to make this situation much worse in the future. Rising sea levels in Europe are a pressing issue, “extreme events may cause severe economic impacts. With no additional investments in adaptation, global damage due to coastal flooding could reach between 93,000 and 961,000 million euros” (Abadie et al., 2020). There must be preventative measures put in place.
Adapting to Rising Sea Levels
Rising sea levels cause increasing costs for coastal cities, so it is necessary to adapt to these impacts if the adaptation is less costly than the future damages. Coastal areas are also some of the most populated places on Earth (Brown et al., 2018). Reducing the harsh economic effects requires adaptation techniques, including protecting land from sea-level rise. Hinkel et al. (2014) report that the global costs to use and maintain dikes to prevent coasts are USD 12–71 billion in 2100, which is still significantly less than the total cost of avoided damages (Hinkel et al., 2014). Neumann et al. (2015) declare that adaptation is the most cost-effective measure as well. This displays that adapting to sea-level rise due to climate change can help lower the future economic implications for cities on coastlines. The technique used for adaptation is important, as Hinkel et al. (2014) note that it is important to estimate the costs of coastal flooding to determine appropriate adaptation strategies as well as account for uncertainties of socioeconomic development. See Table 1 for a summary.
Table 1: Research on Costs of Sea Level Rising
| Skip Table 1 | ||||
| Source | Key Points | Economic Impact | Adaptation Costs | |
|---|---|---|---|---|
| Ralls (2023) Abadie, Murieta, & Galarraga (2020) |
Estimated losses over $1 trillion by century’s end due to sea-level impact on coastal cities. | Direct damage to infrastructure (roads, bridges, ports). | — | |
| Hinkel et al. (2014) | Costs of using and maintaining dikes | Avoided damages are significantly higher than adaptation costs. | USD $12–71 billion by 2100 | |
Assessing Mitigation & Non-Mitigation Scenarios
Brown et al. (2018) assess the impacts of mitigation and non-mitigation scenarios on flood plain areas. They analyze the sea-level rise and coastal floodplain areas, finding that mitigation can help reduce projected floodplain areas, and the difference between mitigation and non-mitigation for floodplain areas is greatest in 2300 (Brown et al., 2018). Brown et al. found that the floodplain in 2000 was 54 million hectares. In the future, the floodplain will be about 62.5 million hectares under mitigation in 2100 and 163 million hectares under no mitigation in 2300, which is a larger difference than in 2000-2100 (see Table 2) (Brown et al., 2018). However, Brown et al. (2018) report that even if we do reduce GHGs and slow temperature rise, sea levels will still slowly increase well into the future, which is why adaptation is so important as well.
Table 2: Impact on Flood Plain Under Different Scenarios.
| Skip Table 2 | ||||
| Year | Scenario | Flood Plain Area (millions of ha) | Population Exposure (%) | |
|---|---|---|---|---|
| 2000 | Baseline | 54 | — | |
| 2100 | Mitigation (Median) | 62.5 (5th and 95th percentile: 58-70) | — | |
| 2300 | Mitigation (Median) | 78.5 (5th and 95th percentile: 61-129) | 1.5–5.4 | |
| 2300 | Non-mitigation | 163 (5th and 95th percentile: 119-222) | 1.2–7.6 | |
Note. Population exposure percentages for 2300 assume no population growth after 2100 (Brown et al., 2018).
Conclusion
Overall, this short commentary finds that the economic damage caused by rising sea levels is extensive, and rising sea levels will also have major implications for floodplain areas. Many people will be affected if no mitigation or adaptation strategies are adopted. Policies and protective measures must be put in place before the damage to coastal cities is irreversible, therefore making them unlivable.
Media Attribution
Figure 1: “6 m sea level rise” by NASA (2012), via Wikimedia Commons, is in the public domain.
References
Abadie, L. M., de Murieta, E. S., & Galarraga, I. (2020). The costs of sea-level rise: Coastal adaptation investments vs. inaction in Iberian coastal cities. Water, 12(4), Article 1220. https://doi.org/10.3390/w12041220.
Brown, S., Nicholls, R. J., Goodwin, P., Haigh, I. D., Lincke, D., Vafeidis, A. T. & Hinkel, J. (2018). Quantifying land and people exposed to sea-level rise with no mitigation and 1.5°C and 2.0°C rise in global temperatures to year 2300. Earth’s Future, 6(3). 583–600. https://doi.org/10.1002/2017EF000738.
Hinkel, J., Lincke, D., Vafeidis, A., Perrette, M., Nicholls, R. J., Tol, R. S. J., Marzeion, B., Fettweis, X., Ionescu, C., & Levermann, A. (2014). Coastal flood damage and adaptation costs under 21st century sea-level rise. Proceedings of the National Academy of Sciences, 111(9), 3292–3297. https://doi.org/10.1073/pnas.1222469111.
Hummel, M. A., Griffin, R., Arkema, K., & Guerry, A. D. (2021). Economic evaluation of sea-level rise adaptation strongly influenced by hydrodynamic feedbacks. Proceedings of the National Academy of Sciences, 118(29), Article e2025961118. https://doi.org/10.1073/pnas.2025961118.
NASA. (2012). 6m sea level rise [Image]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:6m_Sea_Level_Rise.jpg.
Neumann, J. E., Emanuel, K., Ravela, S., Ludwig, L., Kirshen, P., Bosma, K., & Martinich, J. (2015). Joint effects of storm surge and sea-level rise on US Coasts: New economic estimates of impacts, adaptation, and benefits of mitigation policy. Climatic Change, 129. 337–349. https://doi.org/10.1007/s10584-014-1304-z.
Ralls, E. (2024, January 22). Sea level rise will cost coastal cities over $1 trillion in damages. Earth.com. https://www.earth.com/news/sea-level-rise-will-cost-coastal-cities-over-1-trillion-in-damages/.
