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Isa Kaplan, Regan Kahal, Grace McCarthy, and Jen Mills

Abstract

As the global climate continues to shift, many different environmental changes are being experienced far and wide. One of the most widely known effects of climate change is the global rise of sea levels, which has a large potential to affect biodiversity and extinction rates. Bangladesh is experiencing the challenges many countries have begun to face, like increased groundwater salinity , and erosion. This chapter focuses on three areas: the expansion of the aquaculture industry, the damage being done to the Sundarbans mangrove forest, and the effect that these issues have on the people of Bangladesh.

All around the world, countries like Bangladesh are being impacted by sea-level rise in various ways, especially in coastal regions. Rising sea levels in combination with the increasing frequency of extreme weather patterns have greatly increased the rates and levels of flooding in Bangladesh. Among other effects, this has led to increased groundwater salinity and erosion. When beginning our research into this topic, our group sought to learn both how the biodiversity of wild species and the people of Bangladesh are being and could be affected by sea-level rise. As we continued our research, we began to recognize the sheer scope of the issue, even confined to one country, and narrowed our focus to examine the impacts on Bangladesh’s agricultural industry and on the Sundarbans mangrove forest. By focusing on these two areas, we were able to connect the effects on humans with the effects on other wild plants and animals. Understanding specific relationships between humans and ecosystems such as this may prove to be beneficial in helping humans adapt to a changing environment in conjunction with a rising population.

Our Research Process and Methodology

Our methodology consisted of three main steps. At the start of this project, our goal was to gather as much research on the general topic of sea-level rise in Bangladesh as possible. By doing this, we were then able to start narrowing down which subtopics we wanted to focus on, without having to scramble for more information. The next step we took was to reach out to different experts in the field to gather even more information. We took this opportunity to fill in the gaps in our thought process and to clarify which areas we wanted to focus more on. We also wanted to hear the personal experiences of a person in these areas. Our group was fortunate enough to interview Dr. Stuart Hamilton from Salisbury University. Dr. Hamilton provided us with great information about mangrove conservation that helped solidify the direction we wanted to go in. The last step was the analysis. At this stage in our research, we took a step back to look at all of the information we had and finalized which smaller topics we wanted to explore.

The Expansion of Aquaculture

The Bangladeshi economy is primarily agriculturally based, having marine produce as one of their largest and most valuable products, second only to rice (FAO, 2005). Seafood accounts for about 63% of animal protein intake in Bangladesh (Jahan et al., 2009), and is also their second-largest export industry (FAO, 2005). Due to the rising sea levels, seawater inundation has increased soil salinity throughout much of the region (Chen & Mueller, 2018). The increases in salinity are shown to have negative effects on a range of crops with rice being greatly affected (Zeng & Shannon, 2000). Due to the increase in salinity, land-based agriculture is becoming increasingly difficult to profit from in places like Bangladesh as sea levels continue to rise. One way that many Bangladeshi are adapting to this is by diversifying and shifting their focus to aquaculture, a controlled cultivation of aquatic organisms. From 1990 to 2010, aquaculture in Bangladesh exhibited an average annual growth in production of 10 percent (Jahan et al., 2009).

The Possible Negative Effects of Aquaculture

While aquaculture is capable of providing a highly efficient and adaptable food source for growing countries like Bangladesh, it is also known to have negative effects on surrounding aquatic ecosystems. In countries such as China that have exhibited a similar expansion of aquaculture, negative side effects have been observed (Cao et al., 2007). It is well known that the solid waste products produced from aquaculture can dramatically increase the levels of nutrients such as nitrogen and phosphorus in bodies of water. This build-up of nutrients can lead to eutrophication, which can, in turn, cause algal blooms and reduce the oxygen levels of the water (Mancuso, 2015). One source of this pollution is the wastewater produced from aquaculture. If discharged untreated, the large concentrations of phosphorus and nitrogen increase levels in surrounding bodies of water, making it much easier for algae to reproduce, causing algal blooms and eutrophication. This is made worse by solid waste such as uneaten feed and fecal matter which also contains these same nutrients. As well as this, untreated wastewater can dramatically decrease levels of oxygen due to the decomposition of organic matter (Cao et al., 2007). Open-water cage aquaculture systems are particularly harmful for these reasons due to their high level of exposure and interaction with their surrounding environment.

Another source of environmental harm caused by aquaculture is the use of disinfectants and antibiotics. According to (Burridge et al., 2010), antibiotics used in aquaculture have the potential to affect the local biodiversity of phytoplankton and zooplankton even after being digested, which could have extended consequences possibly affecting land animals and humans. As well as this, the widespread use of antibiotics can lead to the proliferation of antibiotic-resistant strains of various bacteria. This also has the potential to affect myriad animals as well as humans.

The Effects of Aquaculture on Coastal Communities

Growing every year by about 6.1% from 2002 to 2012, aquaculture is one of the fastest-growing animal food-producing sectors worldwide (Abdullah et al., 2017). Increasing sea level rise and salinity levels and reduced freshwater availability have been the main reason for the transition from rice culture to shrimp aquaculture practices. The industry of aquaculture is funded by foreign companies and industries that benefit from the low cost of the land and work in Bangladesh and most of the products are exported for a profit. A study from 264 households in Mongla examining how shrimp aquaculture has affected the livelihoods of people living beside the Sundarbans mangrove forest in Bangladesh found that shrimp income represents about forty-six percent of the total household income for the higher-income households, but just twenty-six percent for middle-income households and eight percent for lower-income households (Abdullah et al., 2017).

The increase in aquaculture will mainly benefit those who come from higher-income households. The lower-income households are being bought out by the higher-income households who already have large plots of land and will benefit from this industry. The people from lower-income families end up in poorly paid jobs working in the aquaculture industry. More than 90 % of those in aquaculture-related jobs either collected shrimp fry for the farms or worked as laborers. Income from shrimp aquaculture in Bangladesh is and has been, beneficial only to the rich. Fifteen years ago, around 84% of the very poor received no income at all from shrimp aquaculture, where the very rich earned around 58% of their total income from shrimp aquaculture (Abdullah et al., 2017). Shrimp income forms an integral part of the higher-income and some middle-income households. As a result, economic growth due to shrimp aquaculture has had a positive outcome for middle- and high-income households that own shrimp farms due to the shrimp aquaculture increasing their income-earning opportunities, but a negative outcome for low-income households.

The Ecosystem Services that Mangroves Provide

The Sundarbans is a mangrove forest spanning 4,000 square miles of both India and Bangladesh. It is the world’s largest continuous mangrove forest and is home to a wide variety of species. Due to its large size, it serves as a natural barrier against tides and cyclones and absorbs storm surges. Unfortunately, due to climate change and human activity, the forest has been exponentially shrinking over the years. There are multiple reasons why it is shrinking, including the salinity of the water and illicit logging. The increase in salinity comes from both the rising seas and upstream dams that are reducing the freshwater flow into the Sundarbans. Another downfall in the rise in salinity is that it kills off higher value, storm-stopping tree species like the Sundari. This is very important because this species and multiple other tree species contribute to the coastal protection of Bangladesh. Mashfiqus Salehin is a professor at Bangladesh University of Engineering and Technology’s Institute of Water and Flood Management and commented that “The salinity front is just going up and up and up. New areas will salinize, and moderately salinized areas might become unlivable. It’s becoming a big problem” (Schwartzstein & Datto, 2019). Illicit logging is the process of cutting down trees and using wood for building materials to house the population. This depletes the mangrove population drastically.

Due to these reasons leading to a depleted mangrove population, the stabilization of the coastal land is now compromised. With the absence of the tangled roots of the mangroves giving structure to the land, it erodes into the sea. In addition, the land is not replenished as it once was due to the upstream dams blocking the river flow. An example of how much the land has eroded due to the depleted mangrove population is three islands in India’s Hugli River: Lohachahara, Suparibhanga, and Bedford. A century ago, these islands were covered in mangroves but they have since vanished. Another island that has been affected is Sagar Island, which is an island in India that lies on the Bay of Bengal. Since the mid-20th century, the size of Sagar Island has shrunk by 20 square miles (Schwartzstein & Datto, 2019). Another issue this island is facing is the drastic increase in population due to new arrivals coming from disappearing neighboring islands. This ties into how the local communities are drastically affected by the lack of coastal protection from the mangroves and the sea levels rising as a whole.

The Changing Biodiversity of the Sundarbans

The Sundarbans of Bangladesh contain some of the most diverse ecosystems in the world. As a biodiversity hotspot, it is home to 334 plant species, 49 mammalian species, 59 reptilian species, 210 whitefish species, 24 shrimp species, 14 crab species, 43 mollusks species, and around 260 bird species (Uddin et al., 2018). It is also home to many endangered species including the Royal Bengal tiger, the only tiger known to reside in mangrove forests. These species are in danger, as deforestation and salinification destroy sources of food and shelter for both plants and animals. The rising sea levels are causing seawater to have a higher salt content. When temperature increases, water is evaporated at a higher rate, leaving behind a very high salt concentration in the remaining water (Uddin et al., 2018). The seawater containing a very high concentration of salts destroys vegetation and soil fertility in the region. It also creates a lack of drinking water. These species have little to no access to drinking water and are left with increasing rates of dehydration. Habitats are also being destroyed, especially those of marine life as conditions become unlivable.

Silvo-Aquaculture, a Sustainable Aquaculture Alternative

Shrimp farming is expected to contribute to the local economy, but export-oriented production in the hands of big corporations can have damaging effects on the surrounding environment and ecosystems. Over 50% of the global shrimp for consumption is still obtained through shrimp farming, which is a key cause of mangrove destruction. A sustainable form of aquaculture is needed in order to protect the ecosystems of the Sundarbans in Bangladesh. Sustainable silvo-aquaculture is when mangrove trees are planted alongside shrimp ponds or shrimp ponds are placed alongside certain mangrove species. It replicates a more natural habitat and allows for profitable net income from shrimp farming. This type of aquaculture is considered organic farming and it increases the mangrove area, maintaining biodiversity by providing a nursing ground for many aquatic and animal species.

It is important to select mangrove species that will be useful and locally acceptable to be used in transitioning the current non-mangrove shrimp culture practice towards a more sustainable shrimp silvo-aquaculture in the coastal regions of the country. There are thirteen mangrove species in Bangladesh that are documented as suitable for use in silvo-aquaculture systems (Rahman et al., 2020). In Vietnam, “The net return from the mangrove-based shrimp farming system was three times higher than the extensive traditional systems due to higher shrimp yields as well as yields from other aquatic products and the timber” (Rahman et al., 2020). Traditional shrimp farming is considered unsustainable in the area because the Total Economic Value of the mangrove ecosystem is substantially higher than the income derived from the harvest of shrimp. The size of shrimp aquaculture plants has expanded, but a decreasing trend of shrimp production over the time period from 1995–2015 has been reported. The decrease in shrimp production is mainly due to the degradation of the local coastal ecosystem including biodiversity loss, an increase in pollutants, and the degradation of water and soil quality (Rahman et al., 2020). In many areas of Bangladesh, coastal erosion is getting rid of natural habitats and natural mangrove nursery areas.

A total of 13 species of mangrove trees are commonly used in the silvo-aquaculture practice in different tropical countries. The four genera of mangroves represented by more than one species are Avicennia, Rhizophora, Sonneratia, and Xylocarpus (Hossain, 2015). Avicennia alba is established due to its high tolerance of salinity and its use for timber, fuelwood, and house construction materials. It is found in the low to mid-intertidal levels of the mangrove forest under full sunlight in silt deposited muddy soils. The leaves are 6–15 cm in length and are used as fish feed and fodder (Hossain, 2015). Another species, Rhizophora apiculata, is an evergreen light-demanding species with a slow growth rate. It is a lower-mid intertidal species with a preference for deep muddy soils. Leaf length varies from 8 to 19 cm and the wood has an economic value in the form of timber, fuelwood, charcoal, and poles. (Hossain, 2015). Sonneratia apetala is an evergreen fast-growing pioneer that grows up to 20 m in height and has a leaf length of  6–13 cm. This species possesses pneumatophores and is very salt tolerant. Because of these qualities, S. apetala was intentionally planted in the coastal areas of Bangladesh (Hossain, 2015). Lastly, Xylocarpus granatum reaches a medium height of around 20 m and develops a narrow crown. It is a mid to upper mangrove forest species typical of low salinity areas and produces edible fruits. The species provides fuelwood, timber for furniture and building materials, raw materials for pencil, and veneer production (Hossain, 2015). The research on these specific mangrove species aims to help identify and select mangrove species that are most likely to be useful and acceptable for use in more sustainable shrimp-based silvo-aquaculture in the mangroves of coastal Bangladesh. The use of these species in silvo-aquaculture depends on a variety of factors that include species suitability, species characteristics, species availability, local farmers’ knowledge about the ecological services, and the economic importance of mangrove species (Rahman et al., 2020). The roots of these specific mangroves serve as anchorage and aeration and are also classified as stilt, buttress, or pneumatophore root. Mangrove roots reduce wave energy and abrasion, but only the pencil and knee root types, pneumatophores, really accelerate sediment retention.

Impacts of Sea Level Rise on Bangladeshi Communities

Besides the ecological impacts on Bangladesh, the people in these areas are also affected. The Sundarbans mangrove forest provides many assets to the people of Bangladesh, but most importantly, it provides livelihoods. The loss of the Sundarbans will have countless negative impacts on the people involved with it. Tuhin Ghosh, an associate professor at Jadavpur University in Kolkata, shared that, “the people around the Sundarbans will lose a lot” (Schwartzstein & Datto, 2019). The mangrove forest is a source of honey and its waters are a source of fish. This is a source of sustenance for the people of Bangladesh. Joydev Sardar, the secretary of the Fisherman’s Association in Harinagar, Bangladesh, commented that “The Sundarbans is our mother. She protects, feeds, and employs us” (Schwarzstein et al., 2019). Besides the food that the Sundarbans mangrove forest provides, the forest also provides jobs for the people of Bangladesh. But because the mangrove forest has been shrinking over time, jobs are being lost and people need to find new sources of labor. For example, Sagar Island’s crop-growing conditions have worsened so much that the residents have to find seasonal labor in other locations. Bimol Sardar, a farmer from Bangladesh, shared that, “Because of the water damage, it sometimes seems like only the carpenters have work” (Shwarzstein et al., 2019). But, the communities that are not close to the Sundarbans are also feeling this impact. Ghosh said that cities a far distance away from the mangroves, like Dhaka, Bangladesh, and Kolkata, India, will find themselves, “…extremely exposed to cyclones and storm surges” (Schwarzstein et al., 2019). The people of Bangladesh have also experienced hardships due to sea-level rise in areas other than the Sundarbans. In February 2018, a part of an embankment that holds back the Chunar River west of East Dhangmari, Bangladesh collapsed for the third time in one year. During this event, 16 houses were swept away, devastating each of those families. But, unfortunately, this became a routine tragedy for the locals.

Aquaculture itself is a somewhat new practice around the world so it was initially a fairly unregulated area especially in Bangladesh. The actions that have been taken in the past were nonexistent for the most part with a large amount of freedom placed in the hands of the organizations that work in the field (S. Hamilton, personal communication, December 2, 2020). The unfortunate truth of this matter is that the companies are only looking to profit and not necessarily looking for the most environmentally stable opportunities. This forced the government of Bangladesh to create the Bangladesh Biological Diversity Act of 2012. Here it was detailed that the government would focus on creating plans to “use its biological resources in a sustainable manner”(Alam & Ahammad, 2017). The issue that arises with this is that there are no specific guidelines that were created just simply the promise that they would in the future. The act also stated that it would use the participation of its people to achieve the goals that it had laid out but again, a large amount was promised with little to no actual action. There have been many agricultural farmers along the coastal region of Bangladesh that were forced to move into cities due to the fact that they were not receiving any of the environmental aid from their own government. There were clear missteps of the Bangladeshi government in how they applied the Bangladesh Biological Diversity Act of 2012, but it is also important to note the notable impacts that they are making in recent times.

Aquaculture in Bangladesh has a clear positive future if the same momentum in policies can be continued. One, in particular, is the incentivizing and disincentivizing of adopting new and more ecologically sustainable practices in the realm of aquaculture. This can be done through numerous means such as subsidies, taxation, and fines (Alam & Ahammad, 2017). It is through actions such as these that the government can finally put pressure on the corporations that have been actively damaging the ecosystems of Bangladesh. In addition to these legislative actions, there have been programs put in place to aid in the creation and stability of smaller and locally owned aquaculture businesses (Alam & Ahammad, 2017). The programs have made it far easier for the smaller businesses to obtain loans in order to expand their businesses to the newer standard that they hope to see throughout all of aquaculture. It is with steps such as these that the government is making a positive impact on the area that it controls.

Conclusion

The research that our team has done on a set of specific issues in Bangladesh stemming from sea level rise shows a specific chain of impacts. This causal relationship of sea-level rise affecting the agricultural industry, which in turn affects the environment in negative ways is a series of connected impacts that could occur in many locations as the effects of climate change continue to worsen. The solutions and mitigation strategies that we have compiled may be used in similar situations that are likely to be encountered more frequently in the future as society and corporations continue to utilize aquaculture to meet growing food demand and make a profit for shareholders. The purpose of our research is not to discourage the development of the aquaculture industry, but to shed light on how aquaculture could be implemented while causing minimal damage. Aquaculture demonstrates great potential to fill a gap in food security globally and may prove to be a valuable tool as humans are forced to adapt to climate change.

When researching, the main objective is to solve the initial problem that was laid out at the start. In this case, there are several possible actions to be taken that could aid in the protection of the mangrove environments around the world. One of these solutions would be for the government of Bangladesh to create more protected areas within the Sundarbans. By doing this, the population of mangroves is protected and is more likely to remain at their normal levels as long as the laws are truly enforced by the government. Some actions that the government should take, specifically the Ministry of Aquaculture and Livestock, are to create regulations surrounding how the waste products of aquaculture should be dealt with via treatment and filtration methods. As well as this, regulations need to be put in place limiting the usage of pesticides and antibiotics. Lastly, there need to be recommendations directed towards aquaculture corporations. Based on what we have learned, we believe that it is in the best interest of the surrounding environment that the aquaculture ponds are converted into silvo-aquaculture. In this situation, it may be costly for companies to change their ways. In order to encourage growth in this more ecologically friendly sector, the government of Bangladesh could offer subsidies or benefits to these companies. These recommendations are important for the future of aquaculture as a whole. It is a new and blossoming industry that has a lot of promise in helping the world’s food supply keep up with the ever-growing population.

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