Bangladesh is set to see 50 percent urban population in the next four decades as people are increasingly migrating to the urban areas for livelihoods, education or as fallouts of climate change.

According to a new survey by the Bangladesh Bureau of Statistics (BBS), 74.4 people out of 1,000 migrated to the urban areas from the rural areas whereas only 34 people moved to the rural areas in 2014.

"Presently some 30 percent people of the country live in urban areas, but one third of them in the slums where water, sanitation and healthcare services are quite poor," said Dr Abdur Razzaque, emeritus scientist of icddr,b.

Bangladesh, therefore, will face major challenges of building infrastructures of healthcare, water, sanitation and transport, he said at a seminar organised by the BBS at the Bangabandhu International Conference Centre in Dhaka today.

The country, at the same time, faces another challenge of having more old people in the coming years as life expectancy continues to go up – a fact that will create pressures on the country's economy and healthcare systems.

According to the survey – Bangladesh Sample Vital Statistics 2014, life expectancy at birth of the Bangladeshis went up to 70.7 years in 2014 from 70.4 in 2013. It was 67.7 in 2010.

"People are now living more years due to improvement in overall improvement of health, but at the same time population continues to increase," said Dr Abdur Razzaque.

The rate of natural increase in population is now 1.37 that remained static in the last four years.