Yes, migration can definitely have a positive impact on both the natives and their land. There is a chain reaction that occurs when two cultures or peoples move into the same land. Let's use the example of the population of a city that runs out of food and is forced to migrate. They combine with another city  where resources are less scarce. When people are near each other, population increases. This leads to expanding cities and trade routes. As more people and cultures flow into this city state, it becomes more and more developed and will soon turn into an empire. When cultures come together,  art, technology, and science are all enhanced. Monks, traders, and missionaries travel to the city and spread religion, which unites the people, and starts the cycle over again. Although this seems like a great system, it does have some drawbacks. Overpopulation can mean not enough food to go around, deforestation, and quickly spreading diseases. These things can lead to quickly collapsing empires like the Mongols. However, overall, migration is a positive thing that helps cultures and cities thrive and expand.