Guys I found a nice article by Professor Gani of AIUB. He has very credible credentials to comment on this and he did.
https://www.quora.com/profile/Mohammad-Gani
Why is Bangladesh the most densely populated country on the planet?
Bangladesh is the world’s most densely populated rural country for a very simple reason. It has the most fertile land in the planet.
Look at this: Russia has 116 times the land of Bangaldesh, but produces only 2.09 times the food (in 2019). Bangladeshi land is 56 times more productive than Russian land in the aggregate.
Canada has 68 times the land of Bangladesh, but produces only 1.46 times the food. Per unit area, Bangladesh is 46 times more productive than Canada, in the aggregate.
Just make a calculation: if for more than 50 million years, the Ganges river system carries down at least 4 billions tons of nutrient rich sediments each year and deposits it on one place, how many tons of soil has it accumulated?
While Bangladesh itself is tiny (only 56 k square miles), the rains that fall over 400 k square miles in the Himalayan ranges go to the sea through Bangladesh at the mouth of the sea. Indeed, the country is even today largely beneath the sea level, having risen just out of the Bay of Bengal. It is very active geologically as land-forms are being made and shifted frequently by changing courses of the rivers.
One needs to understand the inventiveness of people who face challenges to make a living. The carrying capacity of the floodplain is identically zero. Under the natural occurrence of annual flood, no human or cattle can survive in Bangladesh (except a small area in the hilly south-east).
But people dug ponds and piled the removed soil on one place to raise a homestead above the flood level. They kept their cattle there, and fed the cattle with dried grass they collected when the grass was plentiful before the floods came. They also learned the art, thousands of year ago, to cultivate a kind of paddy called jali, which literally means watery paddy, that grows madly in flood water, rising with the water at incredible rates of plant growth. That is, a flood resistant paddy.
They also learned, thousands of years ago, to build floating cultivation rafts, by piling hyacinth over hyacinth, on which every kind of food plant is grown in incredible profusion. It is one of the biggest producers of freshwater fish, and it can fill the whole world’s need for drinking water ten times over just from the rain that falls on it directly.
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Bangladesh was always a net exporter of food, and had attracted people from far and way because its food was so plentiful. However, between 1930 to 1980, Bangladesh did experience food shortage owing to fast population growth after a sudden decline in child mortality. But currently, the nation produces 25% more food than it needs. It may appear incredible that on just a bit over 7 million hectares of land (out of 14300 million hectares of land in the planet), Bangladesh did grow 59.9 million tons of food in 2019, enough to feed 295 million people, though its actual population is no more than 165 million. Bangladesh has sheltered more than 1 million refugees from neighboring Myanmar.
Bangladesh is now one of the fastest growing economies in the world.
It is populated well, but is by no means overpopulated. Pause and think about this: had there been overpopulation, people would have less food per person, and their real incomes would fall. But Bangladesh has more food per person with a larger population, and dramatically larger per person real income. People in Bangladesh were much poorer when they were far fewer in number. This paradox basically comes from the economy of scale and scope. This is so difficult a concept to grasp that unless you are ready to do a doctoral dissertation on it, you cannot expect to grasp it.
For post-graduate students, here is the task ahead: Let Q be real GDP per person per life-time and N be the size of the labor-force. Take Q as the life-time output of every single person. Find why the population elasticity of output [(dN/dQ)*(Q/N)] must be positive? In laymen’s terms, why would the demand for labor increase if each worker is more productive than before, namely when (Q/N) increases?
Additional task: relate this population elasticity to the population multiplier [(N+dN)/N] .