I think that immigration actually is an ecology/sustainability issue. There are economic and cultural effects to immigration as well, and that's what people tend to focus on, but they aren't the only issues to consider. I think every country that has their shit together should be giving serious thought to immigration and sustainability, especially knowing that a massive number of climate refugees are coming in the near future. Preparing for that now would go a long way to keeping quality of life up while still helping out.

This specific policy may not be well intentioned, it may even be a means to avoid taking in those refugees when the time comes, but this is the kind of thing that nations should be thinking about right now.