Hello Preearth. Please don't use insults like "...your ability to think logically".

100 years ago the population of the world was about 2 billion. Now it's about 6 billion. Rather than losing land, we gained people, but the effect is the same - 2/3 of the world's population have effectively been made 'homeless'.

As a result, many of them have had to spend a lot of their life working to buy a new house. As you know, it's very common for people to buy their own house rather than inherit it from their parents. However bad this is, it actually happens, and we manage fine.

Keep in mind that this is mostly an intergenerational thing. Most or all current Paris property owners will be dead before their land is flooded.