re: As if the government would listen
For environmental reasons, I think immigration should be limited to match emigration. Many enviros agree, although it's a minority position.
I also think greenhouse gas emissions should be allocated to nations on a per-capita basis as of some year (1980 is as good as any); the per capita amount can increase or decrease depending on how well the nation reverses or fails to reverse population growth, and emigrants should take their allocation with them when they leave.
My $0.02.