As a country with a significantly long coastline, the adverse impacts of saltwater intrusion are substantial on Bangladesh. Salinity mainly affects land and water in the coastal areas.
With the consequence of climate change, it gradually extends towards inland water and soil. This scenario of gradual salinity intrusion into the coastal areas of Bangladesh is very threatening to the primary production system, coastal biodiversity and human health, said researchers.
The total amount of salinity affected land in Bangladesh was 83.3 million hectares in 1973, which increased up to 102 million hectares in 2000 and the amount has risen to 105.6 million hectares in 2009 and continues to increase, according to the country's Soil Resources Development Institute (SRDI).
In the last 35 years, salinity increased around 26 percent in the country, spreading into non-coastal areas as well.
"Salinity which is rising in the coastal areas of Bagerhat, a southwestern district, is having a huge impact on the environment. Production of various crops has declined due to excessive salinity in soil," advocate Mohiuddin Sheikh, president of Rampal-Mongla Embankment Implementation Committee, told UNB.
Once, huge coconut and betel trees were there in the area, but now has decreased dramatically, he said adding, "The production of seasonal vegetables has also declined. Since the late 80s, the effects of salinity in Rampal and Mongla areas have been hampering the local ecology."
Studies conducted by the World Bank, Institute of Water Modelling and World Fish, Bangladesh between 2012 and 2016 have quantified the effects of increasing salinity in river waters in coastal Bangladesh, including the areas in and around the Sundarbans - the world's largest mangrove forest that straddles the coast of Bangladesh and India.
The broad categories of climate change impacts which will affect the coastal areas of Bangladesh are changes in temperature and rainfall patterns, sea-level rise, change in frequency and intensity of cyclones, storm surge, changes in river and soil salinity.
More alarmingly, researchers from the International Centre for Diarrhoeal Disease Research Bangladesh (icddr,b) have noticed an unexpectedly high rate of miscarriage in a small village of Chakaria, near Cox's Bazaar, on the east coast of Bangladesh.
As they investigated further, scientists reached the conclusion that climate change might be to blame.
Khulna region member of Bangladesh Poribesh Andolon (BAPA) MA Savur Rana, a resident of Singarbunia village in Rampal upazila, said, "Once farmers used to harvest Aman (a paddy season) paddy in vast croplands of their areas. But, due to excess salinity, Aman paddy has become extinct."
This has caused a huge impact on the lifestyle of the local people, he mentioned.
Between 2012 and 2017, the icddr,b scientists registered 12,867 pregnancies in the area they have been monitoring for last 30 years. They followed the pregnant women through until the end of the pregnancy and found that women in the coastal plains, living within 20km of the coastline and 7m above sea level were 1.3 times more likely to miscarry than women who live inland.
This difference, the scientists believe, is to do with the amount of salt in the water the women drink - the increase of which is caused by climate change.
Another recent study conducted by the World Bank indicates that climate change will cause significant changes in river salinity in the southwest coastal region during the dry season (October to May) by 2050, and will likely lead to shortages of drinking and irrigation water and cause changes in aquatic ecosystems.
Changes in river salinity and the availability of freshwater will affect the productivity of fisheries. It will adversely affect the wild habitats of freshwater fish and giant prawn. In addition, the salinity increase may induce a shift in the Sundarbans mangrove forest from Sundari (the single most dominant and important species, with the highest market value) to Gewa and Goran.
Estimates from the research indicate that Bagerhat, Barguna, Barisal, Bhola, Khulna, Jhalakati, Pirojpur, and Satkhira districts will be affected most adversely.
This study also identifies soil salinisation in coastal Bangladesh as a major risk from climate change. In the coming decades, soil salinity will significantly increase in many areas of Barishal, Chattogram and Khulna districts. It projects a median increase of 26 percent in salinity by 2050, with increases over 55 percent in the most affected areas.
Due to the rise in soil salinity, Chattogram and Khulna districts are likely to witness the highest within-district additional migration, estimated between 15,000 and 30,000 migrants per year, said another study titled "Coastal Climate Change, Soil Salinity, and Human Migration in Bangladesh", jointly conducted in 2018 by International Food Policy Research Institute (IFPRI) and the Ohio State University.
"These two districts also contain the second and third largest cities in the country. Districts without large cities like Bagerhat, Bhola and Feni will generally expect smaller within-district flows, between 5,000 and 15,000, but larger out-of-district flows, particularly to districts with large cities," said Ohio State University's Joyce Chen, the co-authored of the study.
Meanwhile, after two weeks of bruising negotiations, officials from almost 200 countries on December 15 agreed on universal, transparent rules that will govern efforts to cut emissions and curb global warming.
The deal agreed upon at UN climate talks in Poland enables countries to put into action the principles in the 2015 Paris climate accord.
But to the frustration of environmental activists and some countries who were urging more ambitious climate goals, negotiators delayed decisions on two key issues until next year in an effort to get a deal on them.
The talks in Poland took place against a backdrop of growing concern among scientists that global warming on Earth is proceeding faster than governments are responding to it.