Then slowly the climate change will come for you. Will your borders stop the climate?

To riff on a common quote: if a million refugees want to get into your country and you don’t admit them, the refugees have a problem. If a billion refugees want in, you have a problem.

Nothing “simply” about it.

That's a wrong statement though.

One million people is a single city. You do have a problem if one million people are suddenly relocating. It has happened before for war, natural disasters or other reasons.

Migrating a billion people is not a thing, for the simple fact that there isn't any human settlement any close to approaching a billion people. If you're talking about the scale of a whole continent, migratory flux span over a lifetime and are not homogeneous.

I’m talking from the perspective of the country the refugees are trying to enter. If a million refugees are headed your way and you don’t want to let them in, you can close the border and enact strict immigration controls and you’re fine. Sucks for the refugees, but the target country has no problem aside from the emotional burden. If a billion people are headed your way, you’re fucked.

>Migrating a billion people is not a thing

Yet.

At current numbers, the effect on our own society from our own reaction has cause much more damage to ourselves than the effects from the refugees themselves.

I suspect you may be right that the popular option will be to close the border. I do not agree however, that it is the better option.

It’s caused a divide because the number of current economic refugees is relatively small. Thus many people thought it was possible to have them stay in the first world. Hence the divide in public opinion. But I believe that if the estimates are right, the number of climate refugees will be so high that people will more or less agree that it’s better to close the border in that situation.

>the number of current economic refugees is relatively small

Interesting way to describe people fleeing war.

Economic refugees don't have it good either. Starving and dying from disease isn't easy.

If you are travelling because otherwise you will starve while dying from disease, you are a refugee. Economic migration generally assumes that you are not likely to die from returning. I do not think it is that wise to conflate the terms.

Being too poor to not have enough food, or experiencing a crop failure, does not meet official definitions of refugee eligibility:

https://www.unrefugees.org/refugee-facts/what-is-a-refugee/

It does meet common dictionary definitions though - https://en.oxforddictionaries.com/definition/refugee

Your link’s definition limits it to issues of war, persecution or natural disasters.

A crop failure might be a natural disaster, but lots of other causes of starvation that are not.

Main point is, if you’re seeking refuge, try to put a clear-cut reason down rather than something debatable, but sensible, like absolute poverty.

What happens when the coasts stop accepting refugees from the red states?

This will certainly happen in a scenario where there are massive refugee populations elsewhere in the world.

Oh joy. Grapes of Wrath 2, heavy weapons edition.

Eventually policies like that will lead to mass deaths.