Too Many People
We humans are an odd lot, and boy are there a lot of us. Forget the billions and billions, numbers now so common with money that we just sort of walk away unimpressed. Rather, just think of yourself at a football game or a concert, a protest or a crowded freeway. All those people, and each of them thirsty and hungry and having to shower and poop and all the rest. And that's just a few thousands or tens of thousands. Now multiply that scene throughout the world. It's rather boggling when you stop to think about it, the infrastructure that's needed to support it all...the water and the drains and the sewage pipes that need to go to each home or hotel room or whatever, the food deliveries that have to come from farm to processor to grocery shelf or restaurant, the electrical and gas lines that need to remain hidden but yet need to reach inside each home and building. All of that operating smoothly...unless you're living somewhere on the border of Ukraine.