Supposedly the moors used to be forests, and got the way they are today because of soil depletion in prehistory, as a result of slash-and-burn agriculture.

The other big example is the rapid extinction of all that tasty, tasty megafauna.

Yeah, there was great work done on the impact on Mesoamerica from the Mayans.

https://news.utexas.edu/2015/09/03/clues-from-ancient-maya-r...

Prehistoric practices were relatively sustainable because population was extremely low compared to today. It's perfectly fine to cut down some forest to feed your village, it's not a problem as long as global population is less than a hundred million people.

I agree, but I also think that by saying a practice is not sustainable, they mean that if scaled up and run for a long time, it would eventually cause an impact. You can swap out sustainable and scalable and it reads pretty much the same.

So saying "their practices were relatively scalable, since they were at a small scale" sounds wrong, which is why I think you are being downvoted.

Same way "I use gas to drive my truck" isn't sustainable, even if I'm the only one with a truck. The practice isn't sustainable, even if emissions from one person might not have a large impact.

Talking about "scaling up" seems like a very misguided definition of sustainable to me.

Maybe if it was more like "if everyone in similar circumstances lived this kind of lifestyle".

If a forest can safely supply 1000 trees a year, and a certain lifestyle has 300 people depend on that forest and each use two trees per year, then that's sustainable. It doesn't matter that 3000 people per forest wouldn't work. And if a million people all live this way, then they're splitting three thousand forests, so that's fine too.

It's not reasonable to worry about infinite population density, because then nothing is sustainable. And prehistoric practices weren't using up fossil fuels; trees grow back if you let them.

Though even the sustainability of gas is more complicated than "it's not". As far as CO2 goes, there is an amount that could be safely released per year. And if we were at that level, oil reserves would last a long time.

Perhaps globally, but regionally, you're flatly wrong in at least two ways:

First, on a regional level, civilizations could heavily deforest their surrounding ecosystem to the point of devastating it and themselves with long-term consequences. A couple examples are the Romans, pre-modern Britain and of course, the Maya.

Secondly, the productive practices of pre-modern times were far less efficient in many ways than they are today, meaning not only heavy dependence on forest or at least wood resources, but also a much more impactful destruction of forest land for needs that in many societies today are handled without resotrting to wood.

>the productive practices of pre-modern times were far less efficient in many ways than they are today

Increase in efficiency directly leads to increased consumption:

https://en.wikipedia.org/wiki/Jevons_paradox

I agree with @adrianN (impact correlates to population density) with the obvious caveat that the real question is the ratio between the rate of removal and the rate of replacement. In my initial post when I said prehistoric practices were not sustainable, I should have qualified it -- "not ALL prehistoric practices were sustainable." If you live on an island eating moa, a few thousand of you can drive a species to extinction.

Even with a low population, a society's practices can still be devastating to the environment. There are multiple cases of early Native American cities being abandoned because they got too big relative to their previous size and used up all the resources in the area. This is with populations of 5 and rarely 6 digits.