Might lead to kind of "invasion of sea people" scenario but planet-wise.
Middle East has another problem, with their population still growing they're looking towards the future where even without land shrinking it's too much of them, and here they don't have anybody to blame. Same for Africa (which is not drowning, if not in people).
My parents migrated from the Middle East in the 80s due to war so I have an insight in what goes on in their country, people leave for Europe in quest of a better life quite often. They spend lots of $$ on it and they still get rejected and sent back, I've had personal experiences with people doing that. I've been thinking about the situation that could arise, and it's worrying.
Unfortunately, after decolonization Western countries called it a day: The world is saved once more and they don't have to care anymore, except by using it as a bait in internal politics.