The world population is approximately 6.5 billion (6,500,000,000) now and is likely to surpass 9 billion by 2050.
Traveling in vast barely populated countrysides in Europe seem to amaze me, coming from a populous country like Bangladesh. When I describe Bangladesh to a person who has no idea about the country, I say that the major difference you will find that its buzzing with people. If you go to a countryside you will see farmers at work, women washing stuffs in pond water, people walking in street; anything but you will see people.
And it becomes even harder to compare when it comes to size. The area of Bangladesh is 147,570 km² with a population of estimated 150 millions as of now. It has a population density of 1045/km² (11th most populous country in the world). If I compare it with USA then it has an area of 9,826,630 km² (66 times of Bangladesh) with 303 million people (two times of Bangladesh) with a population density of 31/km². Such a huge contrast!
Size of countries based on population. Graph courtesy GeoHive
* The populous world is dominated by some Asian countries
* By Population Mexico is several times larger than Canada
* Nigeria is the black sheep of Africa
This leaves you thinking why we are seeing more and more of this kind of disparity in the world. The places with more population density have degradable living conditions. And how can you manage this much people? For an example a public bus which can last in USA at least 10 years will not be in usable condition in Bangladesh after 1 year from deployment. More resources are required to provide infrastructures in these countries and challenges are high because these fall in the developing part of the world.
And what will happen in the next 50 years when population in these countries will be almost double (Bangladesh has a growth rate of 2%)?
One might want to look at the history of migration of people in the world. This is almost a natural phenomenon as migration happened due to the lookout for available land because of population growth, attraction to the wealth of affluent areas. USA is the perfect example of migrants setting up a new place for living.
But in todays world this phenomenon is controlled by Visa system. Some scientists suggest that because of negative growth of population some affluent countries will require skilled workforce from the developing world. But more and more affluent countries are blocking entries of potential economic migrants and are not even allowing working immigrants. If you are a resident of a third world country then you will find that a Visa (other than work visa) to an affluent country can be awarded to you only if you can show sufficient financial ability. So the idea is keep the poor in those unlivable congested places.
Today's world is becoming tougher and tougher for people of many populous countries. It remains to be seen how people or nature reacts to the blockages of migrations of people to create enough living space. Extreme solutions like engaging in war to encroach lands are also a distant possibility. You never know what will happen if you push people to their limits as they are squeezed out of their living spaces because of population growth.