We inhabit a planet experiencing a daily net population gain (births minus deaths) exceeding 200,000! Yes, that's every day. And the vast majority have a claim on our collective conscience. If you think for a moment that you can even begin to solve this problem for a planet of 6.4 billion people with relaxed borders, then you really need to become more of a world traveller. You need to see what overpopulation does to a nation. And, then you need to consider the depth of cultural and religious convictions that still cause the explosive fertility in these places. Hopefully, we can become more compassionate and thoughtful ancestors.
Let's not close the gate. Let's just restore the traditional levels of immigration into the U.S. There is no reason for this one nation to be accepting more people for permanent resettlement than all other nations in the world combined. Dick Lamm, longest serving Governor of Colorado, and a Democrat, calls this "environmental malpractice."