Comparing the cost effectiveness of nature-based and coastal adaptation: A case study from the Gulf Coast of the United States

PLOS ONE, Nov 2019

Coastal risks are increasing from both development and climate change. Interest is growing in the protective role that coastal nature-based measures (or green infrastructure), such as reefs and wetlands, can play in adapting to these risks. However, a lack of quantitative information on their relative costs and benefits is one principal factor limiting their use more broadly. Here, we apply a quantitative risk assessment framework to assess coastal flood risk (from climate change and economic exposure growth) across the United States Gulf of Mexico coast to compare the cost effectiveness of different adaptation measures. These include nature-based (e.g. oyster reef restoration), structural or grey (e.g., seawalls) and policy measures (e.g. home elevation). We first find that coastal development will be a critical driver of risk, particularly for major disasters, but climate change will cause more recurrent losses through changes in storms and relative sea level rise. By 2030, flooding will cost $134–176.6 billion (for different economic growth scenarios), but as the effects of climate change, land subsidence and concentration of assets in the coastal zone increase, annualized risk will more than double by 2050 with respect to 2030. However, from the portfolio we studied, the set of cost-effective adaptation measures (with benefit to cost ratios above 1) could prevent up to $57–101 billion in losses, which represents 42.8–57.2% of the total risk. Nature-based adaptation options could avert more than $50 billion of these costs, and do so cost effectively with average benefit to cost ratios above 3.5. Wetland and oyster reef restoration are found to be particularly cost-effective. This study demonstrates that the cost effectiveness of nature-based, grey and policy measures can be compared quantitatively with one another, and that the cost effectiveness of adaptation becomes more attractive as climate change and coastal development intensifies in the future. It also shows that investments in nature-based adaptation could meet multiple objectives for environmental restoration, adaptation and flood risk reduction.

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Comparing the cost effectiveness of nature-based and coastal adaptation: A case study from the Gulf Coast of the United States

April Comparing the cost effectiveness of nature- based and coastal adaptation: A case study from the Gulf Coast of the United States Borja G. Reguero 0 1 2 3 Michael W. Beck 0 1 2 3 David N. Bresch 1 3 Juliano Calil 1 3 Imen Meliane 0 1 3 0 The Nature Conservancy, Santa Cruz, California, United States of America, 3 Swiss Federal Institute of Technology, ETH Zurich , Zurich , Switzerland , 4 Department of Ocean Sciences, University of California , Santa Cruz, California , United States of America 1 Anne Ray Charitable Trust , Kingfisher Foundation 2 Institute of Marine Sciences, University of California , Santa Cruz, California , United States of America 3 Editor: Juan A. Añel, Universidade de Vigo , SPAIN Coastal risks are increasing from both development and climate change. Interest is growing in the protective role that coastal nature-based measures (or green infrastructure), such as reefs and wetlands, can play in adapting to these risks. However, a lack of quantitative information on their relative costs and benefits is one principal factor limiting their use more broadly. Here, we apply a quantitative risk assessment framework to assess coastal flood risk (from climate change and economic exposure growth) across the United States Gulf of Mexico coast to compare the cost effectiveness of different adaptation measures. These include nature-based (e.g. oyster reef restoration), structural or grey (e.g., seawalls) and policy measures (e.g. home elevation). We first find that coastal development will be a critical driver of risk, particularly for major disasters, but climate change will cause more recurrent losses through changes in storms and relative sea level rise. By 2030, flooding will cost $134±176.6 billion (for different economic growth scenarios), but as the effects of climate change, land subsidence and concentration of assets in the coastal zone increase, annualized risk will more than double by 2050 with respect to 2030. However, from the portfolio we studied, the set of cost-effective adaptation measures (with benefit to cost ratios above 1) could prevent up to $57±101 billion in losses, which represents 42.8±57.2% of the total risk. Nature-based adaptation options could avert more than $50 billion of these costs, and do so cost effectively with average benefit to cost ratios above 3.5. Wetland and oyster reef restoration are found to be particularly cost-effective. This study demonstrates that the cost effectiveness of nature-based, grey and policy measures can be compared quantitatively with one another, and that the cost effectiveness of adaptation becomes more attractive as climate change and coastal development intensifies in the future. It also shows that investments in nature-based adaptation could meet multiple objectives for environmental restoration, adaptation and flood risk reduction. - and the Lyda Hill Foundation as well as the Science for Nature And People Partnership; MWB was also supported by a Pew Marine Conservation Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: One of the co-authors, David N. Bresch executed this work in his function as a lecturer at ETH Zurich, where he now became full professor. The organization (Swiss Re) David N. Bresch has been employed with in the past did not play a role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript and did not provide financial support in the form of authors' salaries and/or research materials. And we can thus state that this past commercial affiliation does not alter David N. Bresch's adherence to PLOS ONE policies on sharing data and materials. Introduction Natural hazards in coastal zones pose high and increasing risks to people, property and habitats [ 1 ]. The combined influence of coastal storms, rising sea levels, urban development, population growth and land subsidence are increasing flood risk in coastal areas worldwide [2±7]. By 2050, flood damage in the world's coastal cities is expected to reach $1 trillion a year [ 8 ]. As sea level rises, tropical cyclones will pose a greater risk of extreme flooding and are likely to inflict the greatest damages on highly populated shorelines [ 4 ]. In the United States (US), climate change and the rise in sea-levels will impact many economic sectors [ 9 ], threaten people [ 10 ] and loss of historic and prehistoric archaeological sites and many other cultural assets [ 11 ]. Globally, it is projected that coastal growth in population and development will outpace progress in risk reduction [ 12 ].The need to upgrade existing flood protection and to plan for future coastal risks is becoming increasingly apparent, but the costs may be daunting [13±15]. However, effective adaptation requires understanding the different drivers of risk from an economic perspective, including coastal development and t (...truncated)


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Borja G. Reguero, Michael W. Beck, David N. Bresch, Juliano Calil, Imen Meliane. Comparing the cost effectiveness of nature-based and coastal adaptation: A case study from the Gulf Coast of the United States, PLOS ONE, 2018, Volume 13, Issue 4, DOI: 10.1371/journal.pone.0192132