Climate change has historically pushed people to migrate. There is widespread belief - fear? - that rising sea levels will force millions of people to migrate out of Bangladesh and Vietnam. If that happens, these migrants will spill into neighboring countries many of which are unlikely to be ready to take on migrants. Many will also sooner or later spread into far away countries in Australia, Asia, Europe and North America.
What concerns me more is that this simplistic viewpoint has very little factual analytical backing. Data on migration trends over time are bad. Data on climate change as they relate to migration are even worse. What is worse, migration experts are not necessarily talking to the experts on climate change.