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Habitats, such as coral reefs, can mitigate increasing flood damages through coastal protection services. We provide a fine-scale, national valuation of the flood risk reduction benefits of coral habitats to people, property, economies and infrastructure. Across 3,100 km of US coastline, the top-most 1 m of coral reefs prevents the 100-yr flood from growing by 23% (113 km²), avoiding flooding to 53,800 (62%) people, US2.7billion(902.7 billion (90%) damage to buildings and US2.6 billion (49%) in indirect economic effects. We estimate the hazard risk reduction benefits of US coral reefs to exceed US1.8billionannually.ManyhighlydevelopedcoastlinesinFloridaandHawaiireceiveannualbenefitsofoverUS1.8 billion annually. Many highly developed coastlines in Florida and Hawaii receive annual benefits of over US10 million km–1, whereas US reefs critically reduce flooding of vulnerable populations. This quantification of spatial risk reduction can help to prioritize joint actions in flood management and environmental conservation, opening new opportunities to support reef management with hazard mitigation funding.
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Articles
https://doi.org/10.1038/s41893-021-00706-6
1Institute of Marine Sciences, University of California, Santa Cruz, CA, USA. 2Pacific Coastal and Marine Science Center, United States Geological Survey,
Santa Cruz, CA, USA. 3Center for Integrated Spatial Research, University of California, Santa Cruz, CA, USA. e-mail: breguero@ucsc.edu
Tropical storms represent the most common and costliest
natural disasters across the United States and globally13.
Communities in low-lying coastal zones are currently some
of the most at risk from natural hazards but also increasingly threat-
ened by rising sea levels4,5, intensifying storms, more powerful
ocean waves6 and expanding coastal development79. As storm costs
mount, communities are increasingly looking for effective mea-
sures to protect low-lying coastal communities that do not cause
negative environmental impacts and that can contribute to coastal
sustainability10,11.
Ecosystems such as reefs, beaches, dunes and wetlands
provide an effective first line of defence against these hazards and
represent a promising option to adapt to the increasing climate
impacts1214. However, these protection services are disappear-
ing as ecosystems continue to be lost at alarming rates globally
from both natural and human pressures15,16. These losses could esca-
late flood risk17 in just years to levels not anticipated by sea-level
rise for decades or a century18. Multilateral agencies (for example,
the World Bank), government agencies (for example, US Army
Corps of Engineers, USACE) and even the insurance industry
increasingly acknowledge the role of ecosystems in reducing losses
and risk13,19 but alignment of hazard mitigation and environmental
management is still widely lacking20. Coral reefs are one of the most
diverse ecosystems but also one of the most effective natural barri-
ers against the impacts of storms14,17,21,22. In the United States, coral
reefs line >3,100 km of the most at-risk coastlines across Florida,
Hawaii and the US Trust Territories. However, recent measure-
ments in Hawaii, Florida and the US Virgin Islands (USVI) indicate
that coral reefs have eroded more than 1 m vertically over the past
decades23. These trends are likely to be exacerbated in the future
due to climate change effects and anthropogenic stressors to coral
reefs2426.
Coral reef management and restoration can improve reef
health but it will require increasing resources27,28. Funds dedi-
cated to coral restoration and conservation are very limited com-
pared to funding for hazard mitigation, climate adaptation and
storm recovery. In 2018, for example, the United States provided
about US$15 billion for USACE to construct flood and storm dam-
age reduction projects, of which >US$10 billion was dedicated to
States and Territories impacted by hurricanes Harvey, Irma and
Maria29. In comparison, the most ambitious project in reef restora-
tion in the United States, Iconic Reefs in the Florida Keys, proposes
~US$5 million yr–1 (http://go.nature.com/3ceWKx7).
Risk reduction funds could support ecosystem management
goals if the natural coastal protection benefits were valued using rig-
orous approaches required by risk managers. However, few studies
have rigorously addressed the economic value of coastal ecosystems
in reducing damages to coastal communities30. The development of
risk-based valuations of ecosystem-based flood protection has been
limited by the lack of high-resolution data on bathymetry, topog-
raphy, ecosystems and economic assets and the difficulty in mod-
elling complex hydrodynamic processes across large regions. For
these reasons, previous studies do not model flooding directly31,32
or rely on global-scale data and simplified physics-based modelling
approaches17,33. Yet, recent technological and data advances now
make it possible to quantify and directly assess flood losses and
the benefits of coastal ecosystems for reducing them with unprec-
edented rigour and spatial definition.
Here, we considerably advance conventional probabilistic risk-
modelling frameworks17,34,35 to evaluate flood damage for the coral
reef-lined US coasts of the States of Florida and Hawaii and the
Territories of Puerto Rico, USVI, American Samoa, Guam and the
Commonwealth of the Northern Mariana Islands (CNMI). We use
high-resolution data on bathymetry, topography, coral distribution
and cover and socio-economics with state-of-the-art, physics-based
hydrodynamic models that resolve the nonlinear processes of wave
breaking, wave-driven water levels, run-up and coastal flooding at
10-m resolution, across the scale of the nation. Multidecadal wave
and coastal water-level data were used to drive physics-based,
numerical models to quantify the effect of the reefs on nearshore
hydrodynamics and onshore flooding. Water depths and flood
zones were calculated across the coral reef-lined US coasts to deter-
mine the people, number of buildings, direct and indirect economic
impact and critical facilities at risk of coastal flooding. The risk
reduction benefits were calculated as the averted impacts between
present-day coral reefs and a scenario that assumes a 1 m reduction
in reef height, on the basis of historic measurements. These new
approaches and data make it possible to assess the benefits of coral
The value of US coral reefs for flood risk reduction
Borja G. Reguero 1 ✉ , Curt D. Storlazzi 2, Ann E. Gibbs 2, James B. Shope1, Aaron D. Cole3,
Kristen A. Cumming2 and Michael W. Beck 1
Habitats, such as coral reefs, can mitigate increasing flood damages through coastal protection services. We provide a
fine-scale, national valuation of the flood risk reduction benefits of coral habitats to people, property, economies and infrastruc-
ture. Across 3,100 km of US coastline, the top-most 1 m of coral reefs prevents the 100-yr flood from growing by 23% (113 km2),
avoiding flooding to 53,800 (62%) people, US$2.7 billion (90%) damage to buildings and US$2.6 billion (49%) in indirect
economic effects. We estimate the hazard risk reduction benefits of US coral reefs to exceed US$1.8 billion annually. Many
highly developed coastlines in Florida and Hawaii receive annual benefits of over US$10 million km–1, whereas US reefs criti-
cally reduce flooding of vulnerable populations. This quantification of spatial risk reduction can help to prioritize joint actions
in flood management and environmental conservation, opening new opportunities to support reef management with hazard
mitigation funding.
NATURE SUSTAINABILITY | VOL 4 | AUGUST 2021 | 688–698 | www.nature.com/natsustain
688
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... Coral reefs can attenuate 97% of incident wave energy 33 through friction and wave breaking 34,35 by acting as submerged breakwaters. This reduction in wave energy and associated reduced coastal flooding potential has been valued in terms of averted building damages and indirect economic interruption of billions of US dollars annually in the US 36,37 and tens of billions of US dollars annually worldwide 38 . Because of this, coral reefs have become recognized as national, natural infrastructure for coastal protection by the U.S. Coral Reef Task Force 39 . ...
... However, there is still a need to increase pre-disaster mitigation and post-disaster recovery funding opportunities for coral reef restoration for coastal flooding risk reduction at larger scales 40 . This is important as coral reefs have been degrading in many locations worldwide due to climate-driven changes and pollution, and thereby the flood hazard protection has been reduced 36,37,41 and might continue to decrease. This can aggravate the flooding hazard at reef-fringed coastlines globally if no restoration action is taken 42 . ...
... This can aggravate the flooding hazard at reef-fringed coastlines globally if no restoration action is taken 42 . Because such hazard risk reduction funding is based on traditional cost-to-benefit analyses, a more refined valuation of the coastal protection benefits provided by coral reef restoration 37 is essential to increase such funding possibilities. ...
Article
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Coral reef restoration can reduce the wave-driven flooding for coastal communities. However, this protection has yet to be assessed in terms of the reduced risk of flood-driven environmental contamination. Here we provide the first high-resolution valuation of the reduction of flood-related land-based environmental pollution provided by potential coral reef restoration. Along Florida’s 460 km-long coral reef-fringed coastline, coral reef restoration could reduce the risk of sewage and petrochemical contamination by preventing the flooding of petroleum storage tank systems (-9%), onsite sewage treatment and disposal systems (-4%), and wastewater treatment plants (-10%). The present value of critical infrastructure protection and contamination prevention benefits provided by coral reef restoration is 3,413,503,withsomeareasexceeding3,413,503, with some areas exceeding 1,500,000/km. Annually, 48,403 U.S. gal of petrochemicals, 10,404 GPD of wastewater treatment capacity, equivalent to $281,435, could be protected from flooding, demonstrating that coral reef restoration can provide environmental risk reduction and previously undocumented additional socioeconomic benefits.
... Globally, coral reefs protect more than 200,000 people living on the coast from flooding annually (9); these populations are denser, growing faster, and composed of more people from lower-middle income groups than the global average (10). The coastal protection benefits provided by corals reefs (which extend hundreds to thousands of meters in the cross-shore direction) in the US were assessed using a rigorous, process-based, high-resolution risk modeling system to quantify their defense benefits along the US (11) at more than 18,100 people and $1.8 billion (in 2010 US dollars) in averted flood damages to property and economic activity per year (12). Because of the hazard risk reduction provided by existing coral reefs, reef restoration is increasingly being considered as a hazard mitigation strategy to reduce coastal risk to, and increase the resiliency of, tropical coastal communities (9). ...
... A previous study exploring equity and coastal flooding exposure has examined the socioeconomics of flood risk and finds that minority and vulnerable populations are disproportionately exposed to hazards (38). Another study demonstrates that coral reef loss would disproportionately affect minorities and the most vulnerable (children, the elderly, and low-income) people in the US, particularly in the territories (12). However, these results offer first insight into how different hazard risk mitigation could prioritize return of investment by factoring economic BCRs compared to vulnerable people (39)] than Florida, we explored whether there are significant socioeconomic differences in the protection provided by potential coral reef restoration. ...
... The impact of the 100-year storm's flood zone is a long-standing metric to evaluate the possibility of an area being flooded (41), guides planning and development decisions, and sets financing and insurance rates in the US. For a property in the 100-year flood hazard zone (i.e., 1% chance of flooding in any given year), the probability of being flooded once in a 30-year period (a typical mortgage) is 26% (12). Coral reef restoration could reduce the likelihood of flooding during a 30-year mortgage period by more than one quarter (27%). ...
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Coral reefs can mitigate flood damages by providing protection to tropical coastal communities whose populations are dense, growing fast, and have predominantly lower-middle income. This study provides the first fine-scale, regionally modeled valuations of how flood risk reductions associated with hybrid coral reef restoration could benefit people, property, and economic activity along Florida and Puerto Rico’s 1005 kilometers of reef-lined coasts. Restoration of up to 20% of the regions’ coral reefs could provide flood reduction benefits greater than costs. Reef habitats with the greatest benefits are shallow, nearshore, and fronting low-lying, vulnerable communities, which are often where reef impacts and loss are the greatest. Minorities, children, the elderly, and those below the poverty line could receive more than double the hazard risk reduction benefits of the overall population, demonstrating that reef restoration as a nature-based solution can have positive returns on investment economically and socially by providing protection to the most vulnerable people.
... Altering characteristics of the physical and socioeconomic environment has impact on the livability of urban and suburban areas (Najafi et al. 2024). Proactive planning and reevaluation of development and resource management in coastal regions are essential today (Gaur and Simonovic 2015), even if the most severe effects of sea-level rise may not be felt for some time (Hinkel et al. 2013;Afentoulis et al. 2017;Beck et al. 2018;Reguero et al. 2021). ...
... Societal infrastructure in the twenty-first century is at risk, due to combined climate change-related hazards, such as SLR, extreme weather conditions, erosion, inundation, and generally the rapid degradation of natural coastal systems (Beck et al. 2018;Hinkel et al. 2013;Hoggart et al. 2014;Hsiang et al. 2017;Reguero et al. 2021). While the most severe impacts of sea-level rise may still be in the future, the need for proactive planning and a reevaluation of development and resource management strategies in coastal areas is immediate. ...
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The Coastal Resilience Agent-Based Model (CRes-ABM) is introduced, which was created to evaluate the resilience of coastal areas to the effects of climate change, with a particular emphasis on sea-level rise and extreme weather events. The aim is to provide information for developing policies and making decisions about boosting coastal resilience. CRes-ABM simulates stakeholder interactions and adaptation responses within coastal communities by integrating agent-based modeling techniques, geospatial data, and climate change scenarios. On the basis of the CResI index and the effect of adaptation strategies (CResI_adapt), CRes-ABM produces vulnerability-resilience maps. A variety of parameters are used to monitor agent decisions throughout each simulation. We compare the outcomes using historical data (1976–2005) and two custom climate change scenarios (2041–2100). A thorough framework for comprehending and addressing issues related to coastal resilience is provided by CRes-ABM, which makes it easier to make evidence-based decisions about successful adaptation measures. The structure of CRes-ABM allows it to be applied to various coastal regions worldwide, enabling the evaluation of resilience across different geographic, climatic, and socio-economic contexts.
... With the current rise in sea levels, half of the world's sandy coasts are expected to disappear by the end of the century (Gornitz 1991;Vousdoukas et al. 2020, and references therein). In tropical regions, coral reefs serve as natural barriers against waves, storms, and rising sea levels (Beck et al. 2018;Ferrario et al. 2014;Gallop et al. 2013;Reguero et al. 2021;Toth et al. 2023), reducing the impact of waves on coastlines by up to 97% (Ferrario et al. 2014). ...
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This study examines the morphodynamic evolution of the shoreline and coral reef coverage along the Arabian Sea coast of Oman over the past five decades (1972–2022). The Peninsula of Bar Al Hikman, the largest low-lying coastal area in Oman (550 km²; elevations < 10 m), hosts unique, monospecific coral reefs developing under a monsoon climate. Unlike other densely populated, low-lying coastal areas in the Middle East (e.g., the Gulf), the southern Arabian Plate has received limited attention, with few studies addressing its coastal evolution or future environmental risks. By combining sedimentological fieldwork with photo-interpretations of satellite images spanning 50 years, this study documents significant coastal geomorphological changes. The findings reveal a dramatic 60% reduction in the surface area of Bar Al Hikman’s main coral reefs. A significant consequence of this reef shrinkage is the rapid shoreline erosion on the leeward side of the disappearing reefs. Half of the southern shoreline of the peninsula is retreating northward at rates exceeding 1 m/year, with localized section (6%) eroding at extreme rates of over 10 m/year. At this pace, the ongoing reef decline is likely to exacerbate shoreline erosion, accelerate the landward migration of barrier bars and in turn close off lagoonal areas, and threaten intertidal ecosystems. Furthermore, with the ongoing global rise in sea level, a substantial portion of the peninsula is predicted to fall below the annual flood limit by 2050. This will result in the extensive landward migration of coastal sabkhas deeper into the peninsula's interior. Overall, this study provides a baseline for understanding the recent evolution of Oman’s Arabian Sea coastline and underscores the importance of developing policies and coastal management strategies to mitigate the effects of ongoing environmental and sea-level changes.
... The challenges posed by climate change are combined threats of sealevel rise, storms, erosion, inundation, and rapid degradation of natural coastal systems (Hinkel et al., 2012;Reguero et al., 2021). Furthermore, climate change impacts tourism (Monioudi et al., 2018), global fisheries, and aquaculture (Griggs and Reguero, 2021). ...
... The annual economic benefits of coral reefs in terms of avoiding damage from flooding, erosion, or storms have been estimated at between USD 0.8 to USD 1.3 million for Tobago (Burke et al. 2008), USD 120 to USD 180 million for Belize (Cooper et al. 2009), and USD 700 to USD 2,200 million for the Caribbean (Burke and Maidens 2005). Reguero et al. (2021) found that benefits from coral reefs for US coastal protection exceed USD 1.8 billion annually, where many highly developed coastlines in Florida and Hawaii receive annual benefits of over USD 10 million km -1 . In addition to coastal protection ES, coral reefs provide many other important contributions to economic activity and human well-being such as biodiversity, food provision, and revenues and jobs associated with tourism (Costanza et al. 1997). ...
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... This and other Life in the Deep animations have been presented to broad audiences, including the American Physiological Summit 2023 keynote lecture and at high-level meetings with the Office of Naval Research and the National Marine Mammal Commission. Data-driven animations and graphics representing the coastal protective benefits of coral reefs accompanied an article in the journal Nature Sustainability [70], [63]. This study was referenced by 21 news outlets and key images we produced were used directly in news outlets and then in two guidance documents developed by the US Army Corp of Engineers on the use of Nature Based Solutions for hazard mitigation [17,16]. ...
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... This aligns with known biases in the evidence base on NbS towards forest ecosystems [1,128]. This is concerning, given the critical role of these ecosystems in supporting livelihoods (grasslands - [129,130]; coastal ecosystems - [131]), climate change adaptation [1,2,108,132] and mitigation [133,134]. Understanding how NbS in these ecosystems can support economic impact, as well as biodiversity and climate benefits, is critical to increase ambition and guide their scaling-up. ...
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Coastal development and climate change are dramatically increasing the risks of flooding, erosion, and extreme weather events. Coral reefs and other coastal ecosystems act as natural defenses against coastal hazards, but their degradation increases risk to people and property. Environmental degradation, however, has rarely been quantified as a driver of coastal risk. In Quintana Roo, Mexico, a region on the Mexican Caribbean coast with an annual tourism economy of 10 billion USD, coral reefs constitute a natural barrier against flooding from hurricanes. This study spatially quantifies the risk reduction benefits of the Mesoamerican Reef in Quintana Roo for people, buildings, and hotel infrastructure. The risk reduction benefits are substantial. For example, the reefs prevented 43% additional damage during Hurricane Dean in (2007) and provide nowadays hazard risk reduction for 4.3% of the people, 1.9% of the built capital, and 2.4% of the hotel infrastructure, per year. The annual benefits are estimated in 4,600 people, 42 million USD damage prevention for buildings, and 20.8 million USD for hotel infrastructure. The study also compares the risk reduction of coral reefs with (i) the protection offered by dunes and (ii) the increase in coastal risk from sea-level rise (SLR). The risk reduction of dunes is more critical where there are no coral reefs offshore and for small return-periods storms. Sea-level rise, however, will make the more frequent storms more impactful and will drive significant increases in annual expected damages across the region. However, we demonstrate that, in coral reef environments, the contribution of reef degradation to coastal risk is larger than the expected increase in risk from SLR. However, the spatial distribution of the risk reduction benefits from reefs differs for people and infrastructure, and in particular for hotels, which receive the most protection from reefs. Furthermore, many sections present larger benefits than the typical costs of restoration. This valuation makes a compelling case for protecting and maintaining this natural infrastructure for its risk reduction service, but also allows the development of piloting innovative strategies, such as risk finance and insurance strategies, that can align environmental and risk management goals.
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The importance of explicitly modelling sea-swell waves for runup was examined using a 2D XBeach short wave-averaged (surfbeat, “XB-SB”) and a wave-resolving (non-hydrostatic, “XB-NH”) model of Roi-Namur Island on Kwajalein Atoll in the Republic of Marshall Islands. Field observations on water levels, wave heights, and wave runup were used to drive and evaluate both models, which were subsequently used to determine the effect of sea-level rise and extreme wave conditions on wave runup and its components. Results show that specifically modelling the sea-swell component (using XB-NH) provides a better approximation of the observed runup than XB-SB (which only models the time-variation of the sea-swell wave height), despite good model performance of both models on reef flat water levels and wave heights. XB-SB has a bias of −0.108 – 0.057 m and scatter index of 0.083–0.639, whereas XB-NH has bias of −0.132 – 0.055 m and 0.122–0.490, respectively. However, both models under-predict runup peaks. The difference between XB-SB and XB-NH increases for more extreme wave events and higher sea levels, as XB-NH resolves individual waves and therefore captures SS-wave motions in runup. However, for even larger forcing conditions with offshore wave heights of 6 m, the island is flooded in both XB-SB and XB-NH computations, regardless the sea-swell wave energy contribution. In such cases XB-SB would be adequate to model flooding depths and extents on the island while requiring 4–5 times less computational effort.
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Sustainable Development Goal 14 of the United Nations aims to “conserve and sustainably use the oceans, seas and marine resources for sustainable development”. Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits that society receives from a healthy ocean. Here we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures—including climate change—are mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, an ethical obligation and a smart economic objective to achieve a sustainable future.
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Coastal wetlands dampen the impact of storm surge and strong winds. Studies on the economic valuation of this protective service provided by wetland ecosystems are, however, rare. Here, we analyze property damage caused by 88 tropical storms and hurricanes hitting the United States between 1996 and 2016 and show that counties with more wetland coverage experienced significantly less property damage. The expected economic value of the protective effects of wetlands varies widely across coastal US counties with an average value of about 1.8million/km2peryearandamedianvalueof1.8 million/km ² per year and a median value of 91,000/km ² . Wetlands confer relatively more protection against weaker storms and in states with weaker building codes. Recent wetland losses are estimated to have increased property damage from Hurricane Irma by $430 million. Our results suggest the importance of considering both natural and human factors in coastal zone defense policy.