The fact that people eat the products of animal agriculture is not an "assumption" - it's measurable data. And something that radically changes the eating habits of billions of people is not small. I personally stopped eating meat last century, but I know from decades of experience that most people have absolutely no interest in giving up meat.

I don’t remember saying anything about convincing anyone. My point is that so many of the numbers involved here are prone to change that the outcome of the equation isn’t anywhere near certain. I was convinced of the benefits of being vegan and made the switch, but I think the biggest driver of people eventually becoming vegan will be regulatory capture of the meat industry leading to mass outbreaks of things like mad cow. Even now, without what is probably an inevitable disaster, beef prices are as high as they’ve ever been and are still climbing, the US cattle herd has been shrinking for years, and wages have largely stagnated for nearly four decades. Veganism or vegetarianism or flexitarianism or not eating red meat may not be a choice, and should that happen the basis of a lot of overpopulation alarmism disappears.

This is completely irrelevant to the question of whether overpopulation is a primary driver of the destruction of our ecosystem. You might as well say that we aren't allowed to discuss environmentalism because of the Unabomber.

Of course it’s not irrelevant, because every instance of policy in the past century and a half I can find on dealing with overpopulation leads to human rights violations. I literally named case after case after case of things like forced sterilization and forced abortion and much of these policies disproportionately lands on marginalized populations. When we just conclude without sufficient evidence that the world is overpopulated and share that unproven position, we run the risk of convincing enough people of that which seems to invariably lead to disaster. Pretending you’re a scientist and have this whole thing figured out, which isn’t the case of course, doesn’t protect you from the likely outcome of policy based on your lay conclusion.

The World Food Programme has studied the global food supply and has experts on staff to analyze their data and have found that there is no global food shortage. That idea, even at our current population, is not reflected in the data. Further, the UN has studied this as well and found that food production has outpaced population growth since the 1960s. The World Food Programme also found that about 1/3 of all food is lost or wasted globally, enough in and of itself to feed a billion people, and that’s without looking at questions of more equal distribution (like maybe the rich countries don’t need to be always eating at ridiculous caloric surpluses on average).

When we look at global hunger, trends emerge right away. A Global issues study found that, in looking at 93 different developing nations, there was zero correlation between population growth and hunger. The strong links are between poverty and unequal income distribution and hunger. ScienceDirect had an article a few years ago on a study of 158 countries over two decades that found that changes in food distribution and undernourishment rates explain more variation in hunger than population growth.

As far as I can find in the literature, there have never been studies that found a consistent relationship between population density and hunger. Every time this is studied, the result is that the bottleneck is access, production vs. entitlement.

It’s not that population has no effect, it leads to increased demand for food, it strains weak systems, and it amplifies existing inequality, but it’s at best a multiplier and not a driving central cause.

Every time we focus on overpopulation instead of failures in economic access, distribution systems, infrastructure, and political institutions, not only do we shield those problems from the scrutiny they deserve but we are accidentally falling in line with those who have pushed policies that tore women’s reproductive systems apart. Beyond that, overpopulation advocates almost always have already given up or at the very least never seem to advocate for policies that could help to slow population without violating basic human reproductive rights via coercion. Fertility declines naturally with development, especially women’s empowerment (education, access to reproductive healthcare, economic opportunity for women, and child survival/low infant mortality). Can you think of a time in conversation regarding overpopulation that someone’s basically said, “What if we tried feminism?” I can’t, genuinely. Maybe I’m just not talking to the right people.