I’m generally aligned with Edward Abbey, except with regard to immigration. While I can sympathize with concerns about overpopulation, I feel that closing borders simply dodges the issue. It would be far healthier to welcome all (open borders) and work to accommodate all in the most sustainable manner possible (obviously, due to overpopulation, this should include a strong family planning policy set, as well as equitable access to higher education, which strongly correlates to declining population growth).
If we close borders, we simply create division and discord, ultimately leading to war and genocide. Non-human life suffers as much if not more than human life under such circumstances.
We have to take care of all life on earth. And that includes humans.
EDIT: I live in a Hispanic community. It really helps me see that our current status of fear mongering around immigration is nothing but. The people who are trying so hard to find asylum in our country right now, are precisely the type of people we should be welcoming with open arms.
EDIT 2: Climate collapse is going to make global migration an increasing necessity. We better get used to it and embrace it. Otherwise we severely risk entering into a sort of climate fascism.