Just as a side note, the woman speaking is named Martha Readyoff, a teacher from New Milford, Connecticut. Just look at her again:
Of course this being a "town hall" and having limited time, Sanders just gave a boilerplate response complete with the "wammen have a right to murder their babies" before making a 30 second response. The question is an important one and deserves a serious discussion.
I have shown this graph before and I am sure I will again. This is what Steve Sailer calls the world's most important graph.
Obviously the problem is not white people having too many kids (or creating too much garbage or pollution for that matter). The most pressing demographic problem that will impact the natural world over the next 50-75 years is the rapidly increasing population in the 3rd world, most notably Africa. This is also the major environmental concern for the world, an exploding population of people who coincidentally don't share the Western concern for the environment. On the path we are on, there are three possible scenarios for Africa and the rest of the developing world.
Scenario One: As Western nations drown in debt they will eventually no longer be able to provide aid to Africa and peacekeeping forces. When that happens there will be a humanitarian cataclysm like the world hasn't seen for hundreds of years. Starvation, disease, war and genocide on an unprecedented scale on a continent with a couple billion people. All the stars singing "We are the world" won't stop it. The death toll will be in the hundreds of millions and it will all happen live for the rest of the world to watch in real-time.
Scenario Two: Like above but guilt stricken Western nations open the floodgate to "refugees" and The Camp of the Saints comes to life. Europe and the U.S. can't handle the flood. Already in Europe in many places the "refugees" that are supposed to fill the jobs left open thanks to Europeans not having children are unemployed at rates of up to 80%. The Western social safety net systems don't work when the number of beneficiaries wildly outpaces the number of contributors. Net result, the same thing happens as in Scenario One, just slightly delayed and now the African apocalypse takes the Western world down with it.
Scenario Three: The West starts to have serious conversations about our responsibility in the exploding population of Africa. Africa's population isn't reaching a sustainable equilibrium because we are subsidizing bad behavior and a suicidal population trajectory. In essence we are enabling their population to grow to dangerous and unsustainable levels out of a misplaced altruism. Again, I am completely opposed to abortion under any circumstances. I can't see murdering a child in the womb as a moral alternative. However, there are lots of other ways to reduce fertility via incentives and contraception. Would I be opposed to putting oral contraceptives in food aid we send to Africa? No. No I would not be opposed to that.
Unfortunately we can't have serious conversations about this because, as with everything, it becomes a racial and cultural issue. We can only scold and hector white people about the environment. Only white people have autistic teenagers sail from one of their nations to another one to repeat the "climate change" talking points they have been trained to say. Even though most of the plastic pollution comes from Asia, we are told we should be guilty about using plastic straws. Really, there is only one culture that cares about the environment and it is Western whites. People in Africa, India, Haiti, South America, most of Asia, don't give a crap. Only we do. Ironically we are told we can't breed for the sake of the planet while people from cultures that cheerfully pollute like crazy have enormous families, and not only are we not allowed to say anything, we are required to subsidize these huge populations and then provide them shelter in our own nations when they wreck the ones they live in. Pointing this out is responded to by screeching about colonialism and white supremacy. Better blacks in Africa starve by the tens of millions than white people point out the obvious.
The question asked by the creepy cat lady teacher was an important one but unfortunately the "solutions" she and Bernie would agree on won't do anything to solve the problem. Africa cannot continue to overpopulate itself and swamp the world. Africans already can't self-manage their own countries, there is nothing to indicate they will be any more successful in other nations.
This issue of third world overpopulation is going to come to a head at some point and hectoring white people about it isn't solving anything. At some point we will have to have a serious conversation about it. The alternative is watching mass starvation on social media.