Institute of Marine Sciences, University of California, Santa Cruz, California, United States of America.
The Nature Conservancy, Santa Cruz, California, United States of America.
PLoS One. 2018 Apr 11;13(4):e0192132. doi: 10.1371/journal.pone.0192132. eCollection 2018.
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.
沿海地区的风险正因开发和气候变化而不断增加。人们越来越关注沿海自然措施（或绿色基础设施），如珊瑚礁和湿地，在适应这些风险方面的保护作用。然而，缺乏有关其相对成本和效益的定量信息是限制其更广泛应用的主要因素之一。在这里，我们应用定量风险评估框架来评估美国墨西哥湾沿岸的沿海洪水风险（来自气候变化和经济暴露增长），以比较不同适应措施的成本效益。这些措施包括基于自然的（例如牡蛎礁恢复）、结构或灰色的（例如海堤）和政策措施（例如房屋抬高）。我们首先发现，沿海开发将是风险的关键驱动因素，特别是对于重大灾害，但气候变化将通过风暴和相对海平面上升的变化导致更多的经常性损失。到 2030 年，洪水将造成 1340-1766 亿美元的损失（针对不同的经济增长情景），但随着气候变化、土地沉降和资产在沿海地区的集中的影响增加，到 2050 年，与 2030 年相比，年化风险将增加一倍以上。然而，在我们研究的投资组合中，一组具有成本效益的适应措施（效益成本比超过 1）可以防止高达 570-1010 亿美元的损失，占总风险的 42.8-57.2%。基于自然的适应措施可以避免超过 500 亿美元的这些成本，并且平均效益成本比超过 3.5，因此具有成本效益。湿地和牡蛎礁恢复被发现是特别具有成本效益的。本研究表明，可以对自然、灰色和政策措施的成本效益进行相互定量比较，并且随着未来气候变化和沿海开发的加剧，适应措施的成本效益变得更具吸引力。它还表明，对基于自然的适应措施的投资可以满足环境恢复、适应和洪水风险降低的多个目标。
