Sea Level Rise: The Impacts and Economic Costs of Sea-Level Rise on Coastal Zones

Submitted by Michael Rastall | published 29th Nov 2012 | last updated 13th May 2019
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Key Messages

  • Coastal zones contain high population densities, significant economic activities and ecosystem services. These areas are already subject to coastal flooding and climate change has the potential to pose increasing risks to these coastal zones in the future. However, the effects of climate change need to be seen in the context of other socioeconomic drivers.
  • The ClimateCost study has assessed the potential impacts and economic costs of sea-level rise in Europe, and the costs and benefits of adaptation. The analysis used the Dynamic Interactive Vulnerability Assessment (DIVA) Model, and considered future climate and socioeconomic change. As floods are probabilistic events, the results are presented as expected annual damage (EAD) costs (undiscounted).
  • For Europe, the mid-range projections for a medium-to-high emissions scenario (A1B(IMAGE)) suggest 37cm of rise by the 2080s, though sea levels will also continue to rise into the 22nd century and beyond. Under an E1 mitigation scenario (stabilisation), which is broadly consistent with the EC’s 2 degrees target, the rate of rise is reduced, with 26 cm projected by the 2080s. However, due to the thermal inertia of the ocean, the two scenarios do not diverge until the 2050s.
  • Under a medium to high emission (A1B(I)) scenario, with no mitigation or adaptation, this study estimates that, annually, 55,000 people (mid estimate) in the EU could be flooded by the 2050s (the years 2041-2070) and, potentially, over 250,000 people by the 2080s (2071-2100). A further 438,000 people may need to move away from coastal areas because of annual flooding. 
  • This flooding, along with other impacts of sea-level rise (e.g. erosion), leads to high economic costs. The annual costs in Europe are up to €11 billion (mid estimate) for the 2050s, rising to €25 billion by the 2080s (combined effects of climate and socio-economic change, based on current prices, with no discounting). These costs include direct impacts, salinisation, costs of moving and land loss. Additional unquantified costs will occur due to ecosystem losses and possible knock-on effects of damage on supply chains.
  • These impacts have a strong distributional pattern. Countries in north-west Europe have the greatest potential damages and costs, although many of these countries are the most prepared for climate change in the European Union.
  • In addition, sea-level rise will affect coastal ecosystems. Wetlands act as natural flood barriers and feeding grounds, and have recreational value. The analysis has estimated that, by the 2080s, over 35% of EU wetlands could be lost unless protective measures are undertaken. Where hard defences are also present, coastal squeeze could result.
  • It is stressed that there is a wide range of uncertainty around these mid estimates, reflecting the underlying uncertainty in the sea-level response to a given emissions scenario and temperature outcome. As an example, while the mid estimate of the number of people flooded in the 2080s is 250,000, and annual estimated damage costs are €25 billion, the ice melt response range varies between 121,000 and 425,000 people flooded, with annual damage costs of between €19 billion to €37 billion. An even wider range results when the uncertainty in projected temperature is considered. This uncertainty needs to be considered when formulating adaptation strategies.
  • Under higher emission scenarios, there is also an increased risk of extreme sea-level rise, with some projections estimating over 1 m by 2100. The study has estimated the potential damage costs from such a scenario, and estimated this would increase the annual damage costs for the EU to €156 billion (undiscounted) by the 2080s – six times higher than that for the A1B scenario.
  • Under a stabilisation scenario broadly equivalent to the EU 2 degrees target, these impacts are significantly reduced in Europe. Under this scenario, the estimated annual number of people flooded falls to 80,000 and the annual damage costs fall to €17 billion (mid estimates) by the 2080s. This mitigation scenario reduces the chance of extreme sea-level rise, an additional factor in the relative costs and benefits between the A1B and E1 (stabilisation) scenarios.
  • Hard (dike building) and soft (beach nourishment) adaptation greatly reduces the overall cost of flood damage. The annual cost of adaptation has been estimated at €1.5 billion in the 2050s (EU, current prices, undiscounted), and achieves a benefit-to-cost ratio of 6:1 (A1B(I) mid scenario). The benefit-to-cost ratios increase throughout the 21st century. However, hard defences need ongoing maintenance to operate efficiently and to keep risk at a low or acceptable level. As the stock of dikes grows throughout the 21st century, annual maintenance costs could approach or exceed annual incremental costs.
  • It should be noted that the costs of adaptation vary significantly with the level of future climate change, the level of acceptable risk protection and the framework of analysis (risks protection versus economic efficiency). Other adaptation options not used in the model may be more costly, but more effective in  reducing flood risk. Sea-level rise should be anticipated and planned for in adaptation policies.
  • The climate and socio-economic uncertainty makes a large difference to the actual adaptation response at a country level. The need to recognise and work with uncertainty – as part of integrated and sustainable policies – requires an iterative and flexible approach. Climate change is only one aspect of coastal management policy in the EU and adaptation to it needs to be positioned within a broader integrated coastal-zone management policy framework.
  • Mitigating for climate change by reducing the rate of sealevel rise is likely to decrease wetland loss, those at risk from flooding, damage costs and subsequent adaptation costs. Mitigation, as opposed to hard adaptation, benefits the natural environment as habitats and ecosystems are allowed a greater time to respond to a challenging environment and climate.
  • These results reinforce the message that the most appropriate response to sea-level rise for coastal areas is a combination of adaptation to deal with the inevitable rise and mitigation to limit the long-term rise to a manageable level. More detailed, local-scale assessments are required to assess and reduce risk to vulnerable areas, including adaptation plans.

Citation

Brown S, Nicholls RJ, Vafeidis A, Hinkel J, and Watkiss P (2011). The Impacts and Economic Costs of Sea-Level Rise in Europe and the Costs and Benefits of Adaptation. Summary of Results from the EC RTD ClimateCost Project. In Watkiss, P (Editor), 2011. The ClimateCost Project. Final Report. Volume 1: Europe. Published by the Stockholm Environment Institute, Sweden, 2011. ISBN 978-91-86125-35-6.