For a good, visceral understanding of the effect of scale, it is helpful to walk though the snow after a heavy storm; before the plows have a chance to hit every street, but after a few early-morning or snow-loving types go out for a stroll. Start, if it is possible, on little neighborhood streets. The ones which don't get a lot of traffic. Places where, even after one or two inches have fallen, only two or three cars have had the chance to pack it down. Their tracks make it easier to walk through the snow, and the cover beside those tracks is still pristine and clean. White enough to eat (if so inclined) newly fallen snow.
It doesn't take much more traffic for this scenario to change. Some roads which still have individual tire-tracks will have clumps of slush fallen from a wheel well marring the landscape. Slightly bigger roads, where there is somewhat steady (but not too steady) traffic, will be a bit gross. The snow now dirty brown, never to be tasted. Slushy, melting, flattened. Almost like it hadn't just snowed one or two inches in the last hour.
Now go up another order: to streets where the traffic is very steady. Almost constant. It is no longer brown and gross: it is black and disgusting. More soot than snow, it no longer attracts attention. It is no longer like it has snowed at all.
Another order up: to interstate highways with never-ending traffic. It is no longer black and disgusting. It is gone. No longer can we even see the effect. It becomes invisible in absence. If you know what your looking for, it is saddening. If you aren't looking for it, you might not be aware there is any problem: that it's just all soot. Soot doesn't only take up a lot of space on the ground, it oftentimes goes up in the air. Now it is everywhere, and there is nothing left of nature. Of those beautiful flat snowfields.
Voila. The effect of scale. One car doesn't do much, but it is never just that one car. Every one is part of a system where the car appears to be the only option. That car is part, and it makes it more necessary (or apparently necessary) for another car; and so on and so forth, until all we have are cars. And, meanwhile, the same holds true for industry, factories, power plants, et al. One factory is not so great an issue. But it is never just one factory. Human scale is that of the interstate.
And now the ominous question: what will happen where the is nothing left of nature?
