In some ways we are our own worst enemy. Medical advances haven't helped as the population booms and lives longer. No massive wars with huge infantry losses helping to keep the population down.
This will be the first time that the world will face a crisis like this and who knows how it is going to pan out. teething problems for sure as UBI will be tweaked per country surely. The cost of living in Finland against the cost of living in Costa Rica will be quite a big difference I am sure. This is not a straight forward system and I wouldn't know what the answer would be.