Flood protection: A natural defense system

Globally, mangroves provide an estimated $855 billion in flood protection services, according to the research of Center for Coastal Climate Resilience at UC Santa Cruz. The Sundarbans itself plays a pivotal role in this contribution, offering irreplaceable protection to Bangladesh’s vulnerable coastal areas, where densely populated communities face recurring threats from cyclones and flooding. Its value extends far beyond national borders, exemplifying the critical importance of preserving such ecosystems for global climate resilience. The Sundarbans, spread over 6000 square kilometers in Bangladesh and about 4000 square kilometers in India, is a critical shield against floods and cyclones for the densely populated coastal regions of Bangladesh. Using advanced flood risk models, researchers have shown that mangroves, such as those in the Sundarbans, reduce storm surges and protect lives, livelihoods, and infrastructure.

The research, conducted by project co-lead, Pelayo Menendez and center director, Michael W. Beck, is featured in the World Bank’s 2024 edition of The Changing Wealth of Nations. As highlighted by the research, the value of mangroves for flood-risk reduction has grown exponentially due to rising coastal populations and increasing climate threats. For Bangladesh, which experiences frequent cyclones, the Sundarbans is a natural barrier that significantly mitigates the impact of these disasters. The devastating Cyclone Sidr in 2007 serves as a stark reminder of how mangroves save lives—areas with dense mangrove cover reported fewer casualties and less infrastructure damage. Furthermore, these natural defenses minimize the long-term economic losses often associated with such disasters.

Biodiversity and livelihoods

The Sundarbans is a UNESCO World Heritage site, home to iconic species such as the Bengal tiger, spotted deer and countless aquatic organisms. It serves as a nursery ground for fish and crabs, ensuring the sustainability of local fisheries. This biodiversity directly supports the livelihoods of millions of people who depend on fishing, honey collection, and eco-tourism. Beyond these tangible benefits, the Sundarbans also holds immense cultural and spiritual significance for local communities.

However, human activities specially brackish water shrimp farming and deforestation have contributed to the degradation of mangroves. Despite this, studies show that the protective benefits provided by mangroves have grown—protecting 61% more people and safeguarding 109% more capital assets from floods in 2020 compared to a decade earlier. This underscores the increasing reliance on these natural assets for coastal resilience. The Sundarbans’ ecosystem services act as a safety net for many vulnerable communities, making its conservation a matter of both ecological and human survival.

Economic and climate benefits

Mangroves, including the Sundarbans, are crucial for Bangladesh’s climate adaptation strategies. By sequestering large amounts of carbon, they help combat global warming. The Sundarbans plays a key role in reducing the country’s vulnerability to rising sea levels and extreme weather events. Moreover, mangroves offer a cost-effective alternative to artificial infrastructure like seawalls, which require significant financial investments and maintenance.

Sustainable aquaculture is gaining momentum as a means of balancing food security with environmental conservation. In Bangladesh, organization like FISHBYTE, an aqua-tech impact startup pioneering efforts to modernize shrimp farming, enabling higher yields from existing land while integrating mangrove restoration into farming practices. Their innovative approach demonstrates how Bangladesh’s low-yield aquaculture can be transformed into climate-smart solutions, supporting biodiversity, enhancing carbon sequestration and reducing the need for land conversion. By incorporating mangrove plantations into aquaculture systems, it exemplifies how environmental restoration can align with economic development, creating a win-win scenario.

The economic benefits of the Sundarbans extend beyond flood protection. The World Bank’s Changing Wealth of Nations report emphasizes mangroves as natural capital assets with long-term value. For Bangladesh, preserving the Sundarbans is not just an environmental necessity but also a smart economic choice. It safeguards fisheries, promotes tourism, and ensures the well-being of coastal communities. The region’s fisheries, for instance, contribute significantly to local and national economies, underscoring the forest’s role in food security and job creation.

Challenges and the way forward

Despite the Sundarbans’ immense value, it faces threats from illegal logging, industrial pollution, and climate change. Rising salinity and reduced freshwater flow from upstream rivers are deteriorating the forest’s health. Additionally, unchecked industrial activities and unplanned urbanization exacerbate these challenges, putting both the ecosystem and the communities it supports at risk. Bangladesh must prioritize mangrove conservation and restoration as part of its national climate-adaptation policies.

Innovative approaches like integrating mangrove restoration with aquaculture demonstrate how sustainable practices can balance economic needs with environmental conservation. By promoting climate-smart aquaculture and integrating mangrove restoration Bangladesh can address the twin challenges of food security and ecosystem preservation.

Investing in the Sundarbans will yield dividends in disaster risk reduction, biodiversity conservation, and economic growth. Learning from global initiatives, such as the Coastal Resilience Explorer tool developed by the Center for Coastal Climate Resilience, can help Bangladesh implement innovative strategies to protect and expand its mangrove cover. Moreover, community engagement and education are critical to fostering a sense of ownership and responsibility for mangrove conservation among local populations.

Global perspectives and local actions

The Sundarbans is part of a broader global network of mangroves that collectively act as climate regulators and biodiversity hotspots. Countries like Vietnam, India, and Indonesia have implemented successful mangrove restoration programs, offering valuable lessons for Bangladesh. These initiatives highlight the importance of government support, community involvement and private sector partnerships in achieving sustainable outcomes. Bangladesh can draw inspiration from these models while tailoring strategies to its unique socio-economic and ecological context.

International collaboration also plays a pivotal role. As climate change knows no borders, global efforts to fund and support mangrove conservation are essential. Bangladesh can leverage its position as a vulnerable yet resilient nation to advocate for increased international assistance and knowledge-sharing platforms focused on mangrove preservation.

Last but not least

The Sundarbans is more than a mangroves forest; it is Bangladesh’s first line of defense against climate-induced disasters and a cornerstone of its environmental and economic resilience. By recognizing the Sundarbans as a natural asset and integrating its conservation into national development plans, Bangladesh can secure a sustainable future for its people while contributing to global efforts to combat climate change.

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Alternative to removing forests to create a way for water bodies, integrated shrimp-mangrove aquaculture preserves at least fifty percent of the land for Rhizophora trees — the native tropical mangroves. In return, the trees provide shrimp, crustaceans, and fish with nutrients, nurseries, and reproductive grounds.

Therefore, this farming technique is practiced throughout the globe including the Mekong Delta of Vietnam.

For many years, ‘integrated shrimp-mangrove’ ponds in the southern Vietnamese province of Ca Mau, on the Mekong Delta, have been lauded for supplying low-cost organic products and stable harvests while preserving mangroves.

This year, however, the harvest is lower than usual, which farmers attribute to recent unusual weather.

During the arid season from December to May, unanticipated rain has altered the brackish water that shrimp require for survival. Moreover, colder-than-usual weather has made it difficult for shrimp to thrive.

“They must spend weeks hibernating in the mud,” says Thac, a 49-year-old farmer. While trapped in the freshwater, they consume very little. The majority die before they reach adulthood, he added.

He said that: “Our shrimp, crabs, fish, and mangroves depend entirely on the environment.” “And when it alters, it ruins everything up, and our wrists are tied,” Thac added.

Integrated mangrove shrimp cultivation is unquestionably lucrative for Thac and other farmers of the region. Since the system produces organic, nutritious prawns in three to four months. These are more expensive than conventionally produced shrimp, fetching up to USD 13 per kilogram, and are in customer demand on international markets such as the European Union.

Thac’s native district of Ngoc Hien, where 23,000 hectares are devoted to integrated shrimp mangrove cultivation, is where the system is most prevalent. However, this year it appears that luck is not on their side. And the majority of producers attribute these conditions to the climate. In fact, mangrove forests play a significant role in determining the climate of this tropical region.

On paper, it appears to be a win-win situation: both mangroves and farmers are benefited. The statistics also support this as the overall amount of mangrove decline in the Mekong Delta owing to aquaculture has decreased from 2,440 hectares annually between 1973 and 1990 to 1,490 hectares between 2010 and 2020.

But integrated farming creates the illusion that mangroves are being preserved, but this is not the case. Despite the attempts of the government and international organizations, mangroves continue to disappear. Changes in sea level, flooding, environmental impact, and the continual operation of upstream hydropower facilities have all contributed to the retreat of mangroves inland.

Furthermore, in recent years, precipitation during the wet season has increased in intensity and frequency, while it has decreased during the dry season. Therefore, the saline water of the Mekong Delta has gotten more salty and less suitable for the survival and growth of mangrove seedlings.

Moreover, tensions continue to exist between forest requirements and aquaculture industry demands. And both climate change, as well as the effects of upland dams, are aggravating the situation.

Therefore, it is not actually a win-win situation. Multiple farmers reported that the leaves of mangrove trees falling into their waters altered their condition. The tannic acid present in mangrove leaves can alter the pH levels of the water. When water parameters change as a result of this, shrimp die.

And compared to shrimp, whose rapid growth helps farmer’s families to profit every three months, it takes mangroves at least ten years to reach the optimal 12-centimeter diameter for timber harvesting which is a huge demerit for this integrated method.

The combined shrimp-mangrove systems were marketed as a ‘win-win’ proposition, but the actual situation proves otherwise. The matter of what can be done in this domain is therefore crucial.

Iris van Duren, a Dutch expert on pond ecology who has worked to promote awareness of the significance of mangroves and the integrated system for the Mekong Delta, states, “It’s a hard way, but there is surely hope.”

However, research indicates that financial incentives for farmers to maintain the mangroves on their land may be a more effective approach than punitive measures taken by regulators.

Jaber Bin Abdul Bari
Department of Oceanography, NSTU

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