As the sea keeps rising due to climate change and affecting coastal Bangladesh, turning the soil and groundwater saline, scientists have been breeding salt tolerant varieties of rice, the main crop in the region. But the sea keeps coming in and turning everything more and more saline, well beyond the point that salt tolerant rice varieties can tolerate.
The latest salt tolerant rice variety – that the scientists released among Bangladeshi farmers as recently as November 20 – can tolerate a salinity of up to 8 deci Siemens per metre (dS/m, equivalent to 512 parts per million).
But salinity is now well above that level in more than half the arable lands in 19 affected coastal districts of Bangladesh.
Researchers say none of the existing varieties of salt-tolerant rice can survive and grow at the level of salinity that has affected both the soil and the groundwater in some of the coastal districts.
According to a study conducted by the Bangladesh Soil Resource Development Institute (SRDI), out of 8.1 million hectares of arable land in Bangladesh, 1.02 million hectares in 19 coastal districts are affected by salinity.
The study also shows that salinity in more than half the arable land in five coastal districts has gone well past the 8 dS/m level. It says out of the 560,000 hectares in five coastal districts – Khulna, Satkhira, Bagerhat, Patuakhali and Barguna – the salinity level now ranges between 8.1 and 16 dS/m. Traditional varieties of most crops can withstand salinity of up to 0.7dS/m only.
“The latest variety of rice we have released can tolerate up to 8 dS/m salinity. It will be damaged if the salinity increases even for a few days,” Jiban Krishna Biswas, director general of Bangladesh Rice Research Institute (BRRI), told thethirdpole.net.
He did hold out the hope that more salt tolerant varieties could be bred in the future. BRRI scientists have already released more and more salt-tolerant rice varieties eight times. But there is a limit to this. Researchers say the tolerance cannot go beyond 12dS/m, a level now surpassed in some areas of coastal Bangladesh.
The SRDI study found that in the last few years, an average of 6,200 hectares of fresh farmland is being affected by salinity every year. In 1973, 833,000 hectares of land in 19 coastal districts were salinity-affected. Now, the figure stands at 1.02 million hectares.
In 12 salinity-affected areas, only a quarter of arable land remains under cultivation – that too in a limited way.