This is an offshoot of the discussion on overpopulationThe Myth of Overpopulation Part 2 The topic of sustainability was raised- this is a big concern of environmentalists. The problem is that experts with doctorates differ wildly about what population level is sustainable; some say as few as 2 billion, others upwards of 50 billion. How's a poor layman to know what is right when the experts disagree?
The first step is to realize that experts are people, too, and so can become attached to pet theories, fail to consider alternatives. Their specializations sometimes induce tunnel vision- this phenomenon is so well known that it spawned an aphorism: "an expert has mastered his discipline from B to Z and forgotten A". This is where common sense and a pocket calculator come in. If you remember your college algebra, I can show you a syllogism that proves 2 = 1; but you don't need a doctorate in math to know that's wrong, you only need your common sense. As Bob Dylan said, you don't have to be a weatherman to know which way the wind blows.
Ok, the first thing to remember is that this is a closed system; other than a couple tons of metal we left on the Moon, what happens on Earth, stays on Earth. The second thing to remember is that we do not exist apart from the environment; we are part of it. The third thing to remember is that life is persistent, it expands to fill the niches. If we, as animals, did not exist, that would not mean fewer total animals on Earth, it would mean other animals would be born to eat what we're not eating- so the actual question is, how much animal life is sustainable on Earth?
An equally hard question. Let's look just at North America, a good microcosm of the whole. A few centuries ago, it was in a natural state, in that the people living here were, speaking only environmentally, living as animals- their art, music, and complex culture was not polluting or depleting the environment. How much animal life was being naturally sustained then? Still too complex; let's take another microcosm, an animal we know something about: the North American Bison, or buffalo.
Experts say there were between 30 and 60 million buffalo; split the difference and call it 45 million. Buffalos run upwards of 2,200 lbs. each; round that down to an even ton. That gives us some 90 billion pounds of animals- what's that in human terms? The average human runs 150 lbs.; that gives us 600 million people! Yeah, yeah, that's overly simplistic, it's not a pound for pound ratio, yada yada. But it's not a meaningless number, either- it really was 90 billion pounds of hot, pulsing mammal flesh, and that was only a single species, ignoring deer and moose and elk and beaver and a couple hundred million squirrels and a couple billion birds and a few trillion insects, all sustained without digging a single well or plowing a single furrow!
Of course, directly replacing the buffalo would mean living like a buffalo- there's a visual for you, 600 million naked vegetarians! People won't live like that- I want my MTV! We have a civilization to maintain, and that takes a lot of resources- resources that we're running out of. Or are we?