History records past migrations due to climate change. There are books written about the Sea People invading countries in the Middle East seeking food and, in the process, leaving a path of destruction in their wake. Geographical borders changed as science records the effects earth’s movement with plates shifting causing earth quakes. “The Earth is in a constant state of change. Earth's crust, called the lithosphere, consists of 15 to 20 moving tectonic plates. The plates can be thought of like pieces of a cracked shell that rest on the hot, molten rock of Earth's mantle and fit snugly against one another.” (Source Wikipedia).
If one believes in science, then one must consider history and scientific evidence along with predictions. As geographical changes occurred millions of years ago, further changes will occur due to the shifting plates. We won’t see it in our lifetime, however we will experience the effects of the slow-moving plates with earthquakes. As sea levels rise affecting coastal regions, other areas will experience drought. Migration will become a natural result as people seek safety and food. I suspect that in the process there will be wars fought resisting the invaders. Today, we are seeing people migrating for economic reasons as they seek a better life causing dissention at borders, both in Europe and the USA. I expect that this phenomenon will increase and that governments should be prepared to deal with it peacefully. Desperation will result in conflict as it did in the past. With the availability of arms, it will be more deadly than medieval weapons of war.