My own take is that you can avoid ecological devastation only through population reduction and in the short term by not up-leveling the Third World via mass immigration and industrialization.
Almost like pulling the ladder from under us after we're at the top. Doubt it would mean anything unless it's backed by sanctions, military action or intelligence operations to topple governments that attempt to pull their countries out of poverty. That would make us decisively "the bad guys", regardless of motive.
Perhaps one answer would be to allow people to swap citizenships. If you are feeling guilty enough, you could move to Lagos and someone there could move to Palo Alto.
Since this would necessitate birth control, it would be in direct conflict with the beliefs of the Catholic Church and couldn’t be supported by the Pope.
What we (the world) will be awash in is Moslems and sub Saharan Africans unless those curves get bent via behavior changes, resource depletion, or war. I can't say that the Pope is much involved in that situation.
Like the 15% of (mostly-sub Saharan) Africa that identifies as Catholic? https://en.m.wikipedia.org/wiki/Catholic_Church_in_Africa
hah. Partly answered.