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

Abstract

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.

The Risk Reduction Benefits of the Mesoamerican Reef in Mexico

“…The simulations of ∼15,000 synthetic storms were generated based on the historical storms (∼900 historical storms) using a stochastic simulation of origins and wind speeds and modeling the hurricane tracks through random walks. The analysis of storms was carried out with the open-source CLIMADA risk model using the hurricane and coastal modules (Reguero et al, 2018b;Aznar-Siguan and Bresch, 2019).…”

“…For each of the synthetic storms, we calculated the wind, wave, and surge fields using global bathymetry from GEBCO and ETOPO in deep waters (National Oceanic, and Atmospheric Administration [NOAA], 2006) and the parametrical models implemented in CLIMADAś coastal module, following methods previously used in Reguero et al (2018b). For the wind field, the model uses a non-symmetric fields model (Bretschneider, 1990).…”

“…It is also broadly unknown whether the magnitude of this contribution relative to other threats such as SLR or the protection offered by other natural defenses, like dunes, which are more generally recognized for their coastal protection service and managed and restored accordingly. Only recently has research started to establish the risk reduction benefits of ecosystems Beck et al, 2018;Menéndez et al, 2018;Reguero et al, 2018b), but their combined effect, e.g., reefs acting with beach and dune systems, have only been assessed in terms of wave attenuation (e.g., Guannel et al, 2016) and not in terms of coastal risk, i.e., probability of socioeconomic losses, which are the metrics directly related to risk management strategies. These factors make it difficult to assess how these natural barriers work together for reducing risk to people and property and how intertwined their services are, while also hampering their consideration in risk management strategies.…”

Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

“…Ecological engineering is currently being trialed, or attempted in earnest, in many locations around the world (Chapman and Blockley 2009, Mitsch 2012, Strain et al 2018). Nature-based or soft-engineering approaches using 'green infrastructure' for coastal defense are preferred over hard engineering approaches in many coastal cities as they have been shown to be more cost-effective in the longer term and can serve multiple functions in addition to flood risk reduction (Temmerman et al 2013, Spalding et al 2014, Reguero et al 2018). However, these solutions are often not adopted due to feasibility (e.g.…”

A review of coastal management approaches to support the integration of ecological and human community planning for climate change

“…Managing for resilience can take several forms, including: 1) resisting change through restoration and maintenance of current conditions, 2) accommodating some level of change after a disturbance, but generally returning to a previous state, or 3) facilitating change either through active management towards a desired new state (e.g., reorganization) or passively allowing for autonomous change (Fisichelli et al 2016). Natural infrastructure, including natural habitats and features designed to mimic natural processes, can serve as an alternative management approach to traditional grey infrastructure for risk reduction and may provide added benefits to socio-ecological systems (e.g., Arkema et al 2013;Reguero et al 2018). These benefits can be characterized as supporting, regulating, culturally sustaining, and provisioning ecosystem services and include enhanced erosion control, recreation and habitat preservation, among others (MEA 2005;Gedan et al 2010;NOAA 2010;Scyphers et al 2011;Grabowski et al 2012;Bridges et al 2015).…”