The practical conclusion to this - for people who are homesteading - is to try to buy a piece of productive land that is "out of the way". i.e. protected by natural barriers, and isolated from major cities. If the land is Not easily approachable by squatters, and not on a main road connected with a large city, then your worries about land invasion are much reduced.

The problem already exists in other countries. For example, in Brazil there are permanent squatters. They live in very poor makeshift camps located beside the roads. This does not occur in all the states of Brazil, but I have seen it in some of them. In that country there is usually a small strip of land that borders the roadway, but it outside the fenceline of the farms. Squatters sometimes live permanently on these small strips of land. The farmers do not like it - and they drive off the encroaching squatters. That's because the arrival of a camp of squatters often means that they will scale the fences and rob food from the fruit trees and the fields.

This is really a global demographics problem. Large farms are owned by large companies, and those companies are controlled by billionaires. But the distribution of the world's wealth is becoming enormously skewed, which throws a much larger number of people into poverty.