Let's take an absolute basic easy-to-see example. More people create more trash and waste. This is undeniable. Take a look at this picture:
This was trash left behind by tailgaters at a Kenny Chesney concert in Pittsburgh, PA. Apparently, some of the tailgaters didn't even have tickets to the show, they just showed up and trashed the place.
Before any of the arguments come out about how there were some bad apples spoiling the barrel, or that it doesn't matter how many people would have been there if they had just acted better, before any of that comes to your lips to say to me, let's stop to think, shall we? Yes, of course, we could act like responsible respectful humans and this wouldn't happen. The fact is, we DON'T, and it does happen. So that's off my table right there.
Instead, let's focus on pure numbers. There were easily 50,000 people at this event. So even if every one of them left just one piece of trash behind, well then right there that is 50,000 pieces of trash. If there had only been 10,000 people there, and each of them left 1 piece of trash, there would be 10,000 pieces of trash there. So, here we see that the increased population had a bigger effect on the environment of that parking lot; they left more trash behind than a smaller number would have.
We can extrapolate,m then, that 7 billion people WILL leave more waste behind than will, say, 5 billion. Or 3 billion, as it was back in the 1950s. That's just pure sense and common logic. 7 billion people WILL use more fresh water than 3 billion, will consume more food than 3 billion, will leave more sewage than 3 billion. This is math. This is fact. This is truth. Reality.
The real question should be, How is environment NOT affected by population growth.
It is affected. Period. It can be said over and over that it doesn't have to be that way, that we can be better, that with the right education and caring, we don't have to put such a strain on the environment and we can be as high in population as we wish.
The thing is, that isn't reality. That isn't how we are living and it's not even the way the tide is turning at present. The truth, now and for the foreseeable future, is this:
This is what 7 billion people looks like. 8 billion will just look worse. Let's fix the problem BEFORE it's an even bigger mess to clean.