We may be seven billion specks on the surface of Earth, but when you're in Bangladesh, it sometimes feels as if half the human race were crammed into a space the size of Louisiana. Dhaka, its capital, is so crowded that every park and footpath has been colonized by the homeless. To stroll here in the mists of early morning is to navigate an obstacle course of makeshift beds and sleeping children. Later the city's steamy roads and alleyways clog with the chaos of some 15 million people, most of them stuck in traffic. Amid this clatter and hubbub moves a small army of Bengali beggars, vegetable sellers, popcorn vendors, rickshaw drivers, and trinket salesmen, all surging through the city like particles in a flash flood. The countryside beyond is a vast watery floodplain with intermittent stretches of land that are lush, green, flat as a parking lot—and wall-to-wall with human beings. In places you might expect to find solitude, there is none. There are no lonesome highways in Bangladesh.
We should not be surprised. Bangladesh is, after all, one of the most densely populated nations on Earth. It has more people than geographically massive Russia. It is a place where one person, in a nation of 164 million, is mathematically incapable of being truly alone. That takes some getting used to.
So imagine Bangladesh in the year 2050, when its population will likely have zoomed to 220 million, and a good chunk of its current landmass could be permanently underwater. That scenario is based on two converging projections: population growth that, despite a sharp decline in fertility, will continue to produce millions more Bangladeshis in the coming decades, and a possible multifoot rise in sea level by 2100 as a result of climate change. Such a scenario could mean that 10 to 30 million people along the southern coast would be displaced, forcing Bangladeshis to crowd even closer together or else flee the country as climate refugees—a group predicted to swell to some 250 million worldwide by the middle of the century, many from poor, low-lying countries.