Impact of climate change in Sundarbans mangrove forest

Tanver Hossain

The Sundarbans is the world’s largest mangrove forest. It covers 9,630 km2 and is located on the border of West Bengal, India, and Bangladesh. Since 1879, the Sundarbans mangrove forest has been managed scientifically. The Sundarbans are one of the most biologically productive natural ecosystems on the planet, with the world’s largest halophytic mangrove forests. The forest serves as a vital buffer for inland areas against the ravages of the Bay of Bengal’s frequent cyclones. The Sundarban of Bangladesh was inscribed in the 798th World Heritage List by UNESCO in 1997 for its outstanding natural value, and the Government of the People’s Republic of Bangladesh declared the Sundarban a World Heritage Site in 1999. The Bengal Tiger (Panthera tigris tigris), Ganges River Dolphin (Platanista gangetica), Irrawaddy Dolphin (Orcaella brevirostris), Indian Python (Python molurus), Estuarine Crocodile (Crocodylus porosus), and around 260 different bird species, including several migratory ones like the Spoon-billed Sandpiper (Calidris pygmaea). Many fish including the migratory Hilsa, call it home (Tenualosa ilisha).

Climate is typically described in terms of the mean and variability of temperature, precipitation, and wind over a period of time ranging from months to millions of years (the classical period is 30 years). Climate change has an impact on natural resources such as water and forests, as well as the communities that rely on them. Ecosystems and biodiversity are under threat from climate change. Some Sundarbans-dependent people are now forced to change their traditional occupations and migrate away from their ancestral habitat in search of a better life. The shrinking of mangrove areas as a result of climate change is said to be having a negative impact on the country’s economy. Climate change is affecting the Sundarbans in numerous ways. Some are:

Rising sea levels: Rising sea levels, for starters, pose a serious threat to these fragile ecosystems. Thermal expansion and the addition of significant amounts of water due to the melting of polar ice caps and glaciers are causing the volume of water in the oceans to increase. Because the Sundarbans’ average elevation is less than one meter above sea level, flooding is a major concern. As a result, any increase in sea level will have a significant impact on the region. Though mangroves are water-resistant, tidal inundation that occurs too frequently or for too long can kill them.

Increasing temperature: The temperature of the waters in the Sundarbans increased at an accelerated rate of 0.5oC per decade between 1980 and 2007, compared to the observed global sea surface temperature warming at a rate of 0.06oC per decade. This rapid rise in sea temperature has serious consequences for aquatic life. Because the Sundarbans are an estuarine delta, this change has a significant impact. Furthermore, it has a negative impact on the health of the mangrove ecosystem.

Water logging: Increased rainfall intensity, which is also expected in the region, would result in increased erosion upstream and increased sediment availability, particularly along the Ganges and its tributaries. In conjunction with prolonged flooding, the latter effect occurs. Such a shift would be more pronounced on the Bangladesh side of the forest, and it could partially offset the permanent inundation of the forest floor.

Increase coastal erosion: Flooding on a regular basis also causes coastal erosion, which can lead to a decrease in total land area. The recent disappearance of some delta islands raises concerns about the future of many other islands in the area. These events cause people to emigrate, resulting in environmental refugees who, in turn, increase population pressures in neighboring regions and urban centers. The disappearance of these islands also poses a serious threat to the region’s diverse biodiversity.

Increase intensity cyclonic storm surge: The Sundarbans are located in a region of the world where major tropical cyclones occur on a regular basis. As wind speeds and precipitation levels continue to rise, it is thought that rising sea levels and temperatures will exacerbate these storms. It could be argued that the intensity of storm surges will likely increase under climate change scenarios, especially in the latter half of the twenty-first century. Cyclonic storms would destroy the forest, its inhabitants, and its resources. A high-intensity event in 1986 and Cyclone SIDR in 2007 devastated the Sundarbans, drowning thousands of its magnificent animals, including the Royal Bengal Tiger, which is a threatened species. The cyclone’s wind also wreaked havoc on the vegetation of a large portion of the forest. High-intensity storm surges, influenced by climate change, would inundate high levees and back swamps that are not submerged in saline water and thus would be affected by salinity.

Increase saline water intrusion: The ingress of saline water into Sundarbans areas that are not tolerant of these conditions is also a cause for concern. Excessive soil salinity can be extremely harmful to ecosystems because salts can accumulate in the soil and impede plant growth. It also endangers the health of freshwater aquatic life like fish and giant prawns. The rising sea level has been observed to push saline water upstream into estuaries and rivers, forcing freshwater life into the last remaining saline-free waters. Furthermore, agriculture is being harmed by high levels of salinity in soils caused by high tides, cyclones, and storm surges, as well as problems with water stagnation, which sometimes extends beyond monsoon seasons.

Loss of biodiversity: The Sundarbans is regarded as one of the world’s most complex and delicate ecosystems. There are 334 plant species, 49 mammalian species, 59 reptilian species, 210 whitefish species, 24 shrimp species, 14 crab species, 43 mollusk species, and approximately 260 bird species in the mangroves. Endangered species include the Royal Bengal tiger, Irrawaddy dolphin, Indian python, and estuarine crocodile. Global climate change threatens almost all of the Sundarbans’ flora and fauna. Every topic discussed in the “Global” section contributes to the loss of forest biodiversity. Plants and animals lose food and shelter as a result of deforestation and salinization (deforestation also literally wipes out plant species). Extreme weather and a lack of preparedness for natural disasters make animals just as vulnerable as humans, a sad reality that human communities frequently overlook. In addition to these topics, other processes are annihilating species of all kinds and contributing to the Sundarbans’ loss of biodiversity. Tourism-related pollution has increased exponentially as the Sundarbans have become a more popular destination for environmentally conscious vacationers.

Some of the warning signs of climate change’s negative effects, such as sea-level rise, water logging, poor drainage, siltation, and seawater intrusion, can already be seen in the Sundarban region. Adaptation of the Sundarbans to climate change may thus require cross-border institutional arrangements in addition to local adaptation. Climate change risks should not be allowed to divert attention away from other critical threats, such as shrimp farming, illegal tree felling, wildlife poaching, and oil pollution from barge traffic, which may already be endangering fragile ecosystems like the Sundarbans even before significant climate change impacts manifest.

Author is an Associate Editor

The Environment Review


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