Asylum seekers are a political issue and the Greens are a political party, and should have policies on many issues not just the environment. The Greens will play a major role in the Senate, and should be well informed on whatever issues are debated and discussed.
Sustainable population is an important issue, and I think you'll find that the Greens do have a policy on this.
Personally I don't care who the political party is that finally gets to govern, what I would like to see is the issues addressed in some meaningful way, not just more idiotic party politics, that achieves nothing. Both major parties have shown themselves to be self interested, or simply puppets of their bedfellows, whether that is the unions or big business.