Sea level rising and its impacts in Bangladesh

Sea level rise (SLR) is the average rise in the level of the world’s ocean or regional sea from specific reference points. There are two ways in which global warming is causing SLR. These are (1) thermal expansion and (2) melting of ice. This is a natural process but is being accelerated by human burning of fossil fuels and other human activities that are releasing into the atmosphere. Global mean sea level (GMSL) has been rising at a rate of 3mm/year since 1993(Chen et al., 2017). The intergovernmental panel on climate change(IPCC) 2013 estimated that average global sea levels have increased by around 3 mm annually since the early 1990s and are expected to further increase from 0.75m to 1.90m during 1990–2100 as temperatures continue to rise. The current global SLR rate is about 3.2 millimeters/year (data tracks since 1993 as observed by satellites).

Satellite sea level observations (source: NASA Goddard Space Flight Center)

SLR has several ecological and socio-economic consequences on water resources, food production, fisheries, health, ecosystems and coastal assets, etc. Bangladesh is located geographically in a low lying deltaic area. The coast of Bangladesh is home to approximately 46 million people(S. Development and Integration 2013).it covers an area of 47,201km2 which is 32% of the total land area of the country. The coastline of Bangladesh is about 710 km long. The community of Living in the coastal areas is all vulnerable to changes in sea level .at local and regional rise of sea level can be highly destructive for the people of coastal areas.

Sea level change

SLR in Bangladesh 1.0–1.5 mm/year along Bangladesh coast (Taylor et al., n.d.).a numerical hydrodynamic model developed by begum and flaming (1997)(Begum and Fleming 1997) showed that a combined effect of an SLR of 2 m and an increase in river discharge by 15–20 % will lead to the worse flooding situation. A 1m rise in sea level would submerge a full 18 % of the total land area in Bangladesh(Minar, Hossain, and Science 2013). Research showed that deeply flooded areas (depth above 100 cm, duration more than 9 months) would increase by 29% (from the base year 2000) due to 88 cm SLR by 2100(CEGIS 2006). In the southern region of Bangladesh, it is projected that a 65 cm sea level rise by the 2080s, will result in a loss of 40% of the productive land. About 20 million people in the coastal area have already been affected by salinity(Cell 2009). Another study said that SLR locally In the South West region at Hiron point the mean annual change in water level has been found as 5.5 mm/year. Maximum rise in the water level is observed in the South East region at the Maheshkhali which is 7.4 mm/year followed by 7.04 mm/year in the Sandwip and 5.05 mm/year in the Cox’s Bazar(Nishat and Mukherjee 2013).

Impacts on various sectors of coastal areas of Bangladesh

Impacts on coastal Biodiversity

Coastal ecosystems (mangroves, salt marshes, wetlands, and estuaries) are very sensitive to SLR because they are all interconnected. They supply coastal protection, nutrients, food, and nursery for fisheries, sanctuary, breeding ground, and other ecosystem services. recent research reveals that a 28 cm SLR will cause a decline of 96% tiger habitat in the Sundarbans (Payo et al. 2016). Loss and inundation of the Sundarbans will cause great loss of heritage, loss of biodiversity, loss of fisheries resources, loss of life, and livelihood and after all loss of a very high productive ecosystem. Also, the distribution and habitat of the cetaceans, the Ganges river dolphin, and brackish water species may be affected. Furthermore, 1 m SLR may cause complete losses of the Sundarbans mangroves in Bangladesh resulting in loss of heritage, biodiversity, and fisheries(R. Development, South, and Region 2000).

Coastal inundation and flooding

Sea level rise will increase morphological activities in the river, inducing increased river flow. Accelerated river flow will increase riverbank erosion too(Alam 2003). In Bangladesh, 40% of productive land is projected to be lost in the southern region of Bangladesh for a 65cm sea-level rise by the 2080s. About 20 million people in the coastal areas of Bangladesh are already affected by salinity in drinking water(Kibria 2016). Salinity intrusion due to sea-level rise will decrease agricultural production by the unavailability of freshwater and soil degradation.

source: https://www.grida.no/resources/5648

Saltwater intrusion

SLR will affect seepage and saltwater intrusion in the coastal areas. Seepage may become more saline and effect on agricultural production, aquaculture, and freshwater resources. Sea-level rise will cause saltwater to enter fresh groundwater reservoirs. Saltwater intrusions even now extend as far as 290km inland(Castro Ortiz 1994). The total amount of salinity affected land in Bangladesh was 83.3 million hectares in 1973, which had been increased up to 102 million hectares in 2000 and the amount has raised to 105.6 million hectares in 2009 and continuing to increase(Mahmuduzzaman et al. 2014). With the increasing impacts of climate change, salinity intrusion gradually is going towards inland water.

Food security and agriculture

SLR would cause loss of agricultural land due to flooding of lands and intrusion of seawater as a result of agriculture in low lying coastal area or adjacent to deltas may be affected ((Kibria 2016). A 1.5 meter SLR may submerge 22000 km2 of Bangladesh which will affect about 18 million people. If this happens, rice production and coastal aquacultural production will be significantly hampered.

Storm surge

Global warming intensifies cyclone activities and storm surges. This is causing greater surges and threatening larger areas. This increases the frequency of surges in the coastal area and causes larger coastal inundation. Increase in ocean surface temperature and rising sea levels are likely to intensify cyclonic storm surges and further increase the depth and extent of storm surge induced coastal inundation(Dastagir 2015). The Bay of Bengal in the area of the world having the highest potential for the massive loss of life from a storm surge associated with a tropical cyclone. The frequency of the storms is greater towards the southern parts of Bangladesh, and they occur in Chittagong, Noakhali, Barisal, Patuakhali, and Khulna and some inland areas in Comilla, Faridpur, and Dhaka. (Jakobsen et al. 2006).

Impacts on Health security

Sea level rise may increase the risk of health problems like diarrhea, cholera, etc. During the last 50 years or so the major cholera epidemics that have occurred originated in the coastal region (Colwell and Huq 2001). Rising sea level due to global warming can influence the transmission of salinity tolerant, Aedes spp. (dengue virus) in coastal areas (Ramasamy and Surendran 2012). Increased salinity in the coastal zone will decrease food production in the area, causing malnutrition for the coastal people. So, sea-level rise will accelerate water-borne diseases and malnutrition in the coastal area.

Impacts on Tourism

Tourism is a low-lying fruit that any coastal community can take advantage of to promote domestic jobs. Thus, tourism is an important economic growth driver(Asuncion and Lee 2017). Bangladesh coastal tourist spots are cox’s bazar, kuakata , Patenga , saint martin island, and Teknaf many tourism-related infrastructures are located in these locations. Sea level rising in the coastal area of Bangladesh can affect directly or indirectly in tourism by the coastal inundation or coastal soil erosion.

Impacts on Infrastructure

House, buildings, schools, hospitals, ports, and other economic and social infrastructure which are near to the coast will be at risk due to SLR. Therefore, this is intensifying climate migration toward cities. SLR accelerates soil erosion that washes out the loose topsoil of the coast. Most vulnerable shore types to sea level rise are shoaly, sandy, and silty shore (Press et al. 2015). gradually infrastructure of coastal areas will be poor that is anther negative impact from SLR.

Impacts on Education sector

Education is an important component of development. SLR will cause massive destruction of infrastructure including educational buildings, floods of roads and it will force them to leave their houses, schools. Educational institutes in coastal areas frequently get flooded or ruined and remained closed until reconstruction. Therefore, SLR will drive the loss of educational institutions. If educational institutions will reduce, ultimately the education system of coastal areas will be collapsed. There is a strong relationship between education and livelihood in coastal areas.

some recommendations to tackle of sea-level rise

1: Afforestation is implemented alone coastal belt of Bangladesh. More mangrove plants should be planted. The green belt along the coastline for Bangladesh is the best solution for Bangladesh.

2: More ecological sophisticated adaptive measurements should be taken. So, salt-tolerant rice or brackish fish and shell farming should be introduced in a coastal area that will provide the sustainable livelihood of coastal communities.

3: Protective activities like a seawall, barrier, or automatic coastal water gate that should be able to control remotely. Eco-engineering such as grass and sand made a barrier, shell made barrier can be built. And seawater tolerant infrastructures should be built in the coastal area.

4: community based coastal zone management is more advanced ecological management for Bangladesh. It protects cutting mangroves and provides sustainable livelihood.

5: Bangladesh receives a huge amount of sediments from the Ganges-Brahmaputra-Meghna river system so the new island can be created near shore by tracking, artificial depositing sediment.

6: deforestation should be banned in steps by steps. The government has already taken some steps but integrated and effective management is needed.

7: the introduction of coastal renewable energy (tide, wave, thermal difference, wind, solar) can be harvested efficiently.

8. Redesign coastal area with natural and manmade protection against natural disasters.

Conclusion

The study showed that SLR is a potential threat for Bangladesh coastal community. SLR is a major concern for Bangladesh which can bring a higher cost for the entire economy and ecology of the coastal zone of Bangladesh. Major protective initiatives (dikes, embankments, seawall) along the coastline should be taken to tackle the risks of SLR and natural defense (mangrove, oyster reef, saltmarsh along the coastline) system can be effective. It should be incorporated into all development projects for adaptive, protective, and ecological handling. Infrastructural development livelihood enhancement and ecological balance be prioritized. Climate literacy is important for coastal communities. The western and central coastal zone of Bangladesh is highly susceptible to the risks. The natural and traditional adaptation practices should be evaluated scientifically through habitat research, interaction with communities, and in-depth analysis in the workshops and seminars involving stakeholders for a sustainable national and regional policy for coastal zone management(Ataur Rahman and Rahman 2015). Further research to build an optimistic model for proper SLR by different scenarios is needed. Government and private sectors along with world communities should think and discuss to make advanced and effective policies and steps to reduce the emission of greenhouses that accelerates sea level rise.

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Hafez Ahmad

I am an Oceanographer. I am using Python, R, MATLAB, Julia, and ArcGIS for data analysis, data visualization, Machine learning, and Ocean/ climate modeling.