Bangladesh is experiencing both predictable and unpredictable climate change impacts every year. Sea level rise, increased salinity and drought have become very familiar with our country. Most of the rivers of Bangladesh flow from north to south, silting up the mangroves delta and draining into the Bay of Bengal. The mangrove is a transitional territory between the freshwater rivers originating from the Ganges and the Bay of Bengal. Climate change is affecting many countries of the World but Bangladesh is one of the worst hit where a major portion of population is poor. Climate change poses a high risk to the ecosystems and landmass of coastal Bangladesh. The major threats are high levels of salinity, sedimentation, cyclones, storm surges, water logging and land erosion.
Coastal islands are stores of huge natural resources. The ecosystems are comprised of inland ecosystem, riparian ecosystem, mangrove ecosystem, littoral ecosystem, offshore ecosystem and marine ecosystem. The biodiversity is characterized by flora and fauna of the Sundarbans; seaweeds; coconut trees; screw pine vegetation ; elephant cattail; corals; mollusks, oysters, turtles; crabs; freshwater and marine fishes, sea mammals and reptiles; and migratory birds.
Dune vegetation is being submerged due to sea level rise. Super cyclones Sidr, Nargis, Bijli, Aila and Mahashen impacted the coastal islands through three primary mechanisms: wind damage, storm surge, and sedimentation. The highly affected areas have become unsuitable for habitation till 2020. Strong winds toppled stems, broke off trunks and defoliated the canopy. Taller stems of littoral forests (shoreline forests) were uprooted and knocked over. Sediments carried by storm surges were deposited on the forest floor as the surge receded, caused plant mortality by interfering with root and soil gas exchange. Storm surges reduced the viability of seeds, seedling germination and seedling recruitment. Many exotic plant species rapidly colonized in the devastated areas. Strong wind destroyed honey bee colonies causing high mortality. Coral reefs, woodpecker, sea turtles and parrots were severely affected. Plant debris impacted wetland ecosystems by lowering oxygen levels in the water. Many ground birds lost their habitats, nesting and breeding sites.
Saline water is creeping deeper due to frequent cyclones in the consecutive years. The present threat coming from increased salinity jeopardizes the Sundarban ecosystems. Salinity is more devastating than any other parameter in this territory. It is very difficult to manage salinity because of the lasting nature of its effects on terrestrial and aquatic ecosystems. Most of the tree species are seriously affected when salt concentrates within the root zone. The most significant off-site impact of salinity in the Sundarbans is the salinization of previous fresh water rivers and canals. The habitats of aquatic flora are also degraded by increased salinity. It causes harmful effects on crocodile and dolphin populations. Increasing trend of jellyfish invasion along the coast is a sign of disorder in the Bay of Bengal's ecosystems.
Brackish water from the Bay of Bengal is invading freshwater bodies percolating deep into the soil.
Sundari, the pioneer tree species has been suffering from 'Top dying' disease with the increase of salinity. A declining trend of Sundari tree is observed in Dangmari, Karamjal, Jongra, Mora Passur, Pashakhali, Nandobala, Harbouria, Choraputia, Buddhomari, Katakhali, Boroitola, Jeodhara, Amurbunia, Gulishakhali, Dhansagor, Kolomtezi, Nangli, Chandpai, Mrigamari, Andharmanik, Tamulbunia, Supoti, Bogi, Mora Bogi, Dumuria, Charkhali, Shapla, Chandeshwar, Shoronkhola, Panirghat, Bhola, Dashervarani and Kochikhali forest areas of Sundarban. Keora, Goran and Gewa trees are occupying the lost grounds of Sundari tree. One apprehends after 20 years Sundari trees will be almost disappeared from the Sundarban virtually changing its nomenclature from “Sundarban” to “Keoraban”!
Salinity has severely affected riparian vegetations because they occupy the lowest parts of the landscape where they get submerged by saline water. Nypa palm and mangrove date palm occur most commonly in areas where mixture of brackish and fresh water flows. Declining trends of both palms have been observed in Karamjal, Jongra, Mora Passur, Nandobala, Harbouria, Choraputia, Andharmanik, Tamulbunia and Supoti forest areas. Coconut tree is highly affected by increased salinity resulting in small number of nuts, empty nuts or elongated nuts. The high mortality of screw pine due to increased salinity enhances dune erosion. Seaweed, coral reefs and sea-algae are struggling to remain alive.
There are five forest types in the Sundarbans: fresh swamp, mixed fresh-brackish swamp, brackish swamp, mangrove scrub and littoral forest. Meanwhile, the fresh swamp has disappeared due to increased salinity. Mixed swamp is being converted into brackish swamp. Most of the brackish swamps have become mangrove scrubs.
Bengal Tigers have been suffering from various diseases by drinking saline water, which eventually affects the normal behaviour of this big cat. Many fish species and crustaceans migrate from marine water to freshwater for spawning and juvenile feeding. During the commencement of the south-west monsoon and consequent flooding of all the rivers, Hilsa shad starts its spawning migration towards upstream. Increasing trend of salinity disrupts the migration routes contributing to the decreasing trend of Hilsha abundance. The loss of spawning, feeding and nursing grounds has a profound influence on reduction of Hilsha population to the growing frustration of fishermen of Dubla Island, Supati, Mahipur, Kochikhali, Kotka, Demra Island, Tia Island, Narkelbariya, Hangsharaj, Arpangashiya, Dobayki, Andermanik, Bishkhali, Baleswar, Mathbaria and Pathorghata during catching season. These migrations of fishes have an adverse effect on the economy of the country.
Different surveys show that natural hazards have forced 3.5 millions people living in the coasts to migrate forward and inward. Migration is a tool for survival for the vulnerable. Migration for climate change is a long run disaster because of unpredictable scale and impact. Rarely people migrate by choice, but environmental degradation generates forced migration. Sometimes they move towards the sea instead of inland because of their financial crisis. They cannot afford high lands due to high prices, land disputes and scarcities. They are taken captive by natural calamities. Simultaneously erosion of old lands and accretion of new lands occur. Newly accreted islands welcome homeless and landless people to live and enjoy natural resources. These islands offer highly fertile lands, forest products, fisheries and other coastal resources. But after a period of time the migrants become frustrated finding their habitats overpopulated and eroded. Consequently they start their bon voyage to newly emerged remote islands. This scenario is very much apparent in Bhola and Noakhali districts.
Raise your voices for
Preparing environmental risk atlas: Risk atlas will define the vulnerable places and populations facing the most risk from the onset of climate change. This will be developed to identify exposure; vulnerabilities; and risks to populations, ecosystems, biodiversity, supply chains, investments, natural resources and infrastructures. Risk atlas will display hazard, exposure and risk maps. Hazard maps should be available for 12 hazard types: salinity, floods, landslides, mudflows, sedimentation, erosion, drought, water logging, cyclone, windstorm, hailstorm and northwesterly winds.
Ecosystem based adaptation in coastal areas: The Sundarbans comprising of luxuriant biodiversity can accelerate natural resilience to the impacts of climate change by reducing exposure and vulnerability of the poor people. It can stand as a great wall against storm surges. The biodiversity and ecosystem services can be counted as a natural capital. This capital can be utilized in a sustainable manner to improve livelihoods of the vulnerable people.
Process-based modeling of (agro) forestry in saline area: The proper selection of salt tolerant tree and crop species can increase the productivity of degraded land. Establishing plantations on highly saline soil with minimal investments can reduce bio-drainage in the coastal areas.
Climate resilient livelihoods through community engagements: The involvement of neighbouring people or communities in natural resource management can reduce threats to biodiversity; they would adapt to climate change impacts, and improve livelihoods. Benefits from the ecosystem services and communities' engagements in nature conservation will be mutually exchanged.
Green the blue: From home to a cruise liner there are millions of ways we can keep our water clean and blue. Clean water is the single most important building block of ecosystems around the world. We should go for the green. When we do something, it is essential that those activities boost the green as well as our economy. Every single step of an individual should help to solve our social and environmental problems.
Green economy: A green economy focuses economical growth and employment reducing carbon emissions and pollutions, accelerating sustainable development with minimum utilization of natural resources and ecosystem services. Ecosystems or biodiversity finance and natural capital are the two major components of a green economy, which directly valuates ecological services and treats natural resources as natural capital.
The writer, a biodiversity specialist, is UNO, Mongla, Bagerhat (mizan_peroj @yahoo.com)