The Global Value of Mangroves for Risk Reduction
TNC scientists and partners at the Environmental Hydraulics Institute IH Cantabria have produced a ranking of countries that receive the greatest risk reduction benefits from mangroves, relative to their vulnerability. The Global Value of Mangroves for Risk Reduction–available in both a Summary Report and a Technical Report, linked below–uses rigorous hydrodynamic and economic models to value the coastal flood protection services of mangroves globally, and then identifies the places where mangroves provide the most benefits to people and property. This work applies an approach that is commonly used in engineering and insurance sectors, and quantifies protection benefits of mangroves as the amount of flood damages avoided because of the presence of mangroves.
Coastal development and climate change are significantly increasing the risks of flooding, erosion, and extreme weather events for millions of vulnerable people, important infrastructure, and trade. Coastal ecosystems, particularly mangroves, reduce risk by protecting coastlines against erosion, flooding, and sea level rise and by providing ecosystem services that reduce communities’ vulnerability to hazards. Mangroves reduce exposure to coastal hazards by reducing wave heights and retaining sediments, decreasing the impacts of flooding and erosion and protecting coasts during storms. These natural defenses also provide a wide suite of ecosystem services- including food, livelihoods, carbon sequestration and climate regulation, that reduce the vulnerability of coastal communities to disasters and extreme events, thereby increasing coastal resilience. Mangroves can be managed as natural coastal infrastructure to reduce coastal risks. And unlike most built coastal infrastructure, mangroves adapt and keep pace with environmental change, and they are substantially less costly to maintain.
But mangroves are being lost at an alarming rate, in part because we have not adequately valued these natural defenses. Conventional approaches to measuring wealth focus only on built capital; many critical goods and services, such as flood protection, which rely on keeping ecosystems intact, are rarely valued. This lack of consideration encourages short-term over-exploitation and degradation. Better valuations of the protection services of coastal habitats can ensure that these services are accounted for in policy and management decisions, halting the loss of our natural capital and ensuring the provision of critical ecosystem services.
This report uses rigorous hydrodynamic and economic models to value the coastal flood protection services of mangroves globally, and identifies the places where mangroves provide the greatest risk reduction benefits to people and property. This work applies the Expected Damage Function approach, commonly used in engineering and insurance sectors and recommended for the assessment of coastal protection services from habitats, where the protection benefits provided by mangroves are assessed as the flood damages avoided by keeping mangroves in place. This work combines findings on flood exposure reduction from mangroves with vulnerability scores from the WorldRiskReport and Index to produce a ranking of countries that receive the greatest risk reduction benefits from mangroves relative to their vulnerability. The results are presented in terms of the number of people and the value of property flooded with and without mangroves.
These results demonstrate that mangrove conservation and restoration can be an important part of the solution for reducing the risks of coastal communities. This valuation can inform strategies for adaptation, disaster risk reduction, and environmental management, and can help identify sustainable and cost-efective approaches for risk reduction.
- Mangroves reduce annual flooding to more than 18 million people.
- Without mangroves 39% more people would be flooded annually, and flood damages would increase by more than 16% and US $82 billion annually.
- Vietnam, India, Bangladesh, China, and the Philippines receive the greatest benefits from mangroves in terms of avoided flooding of people.
- China, USA, India, Mexico and Vietnam receive the greatest benefits in annual avoided flood damages to property.
- The countries that receive the greatest overall risk reduction benefits from mangroves are Guinea, Mozambique, Guinea-Bissau, Sierra Leone and Madagascar.