When I was a lad, one of the first computer programmes I had on my ZX Spectrum was called "Foxes and Rabbits".
It was dead simple - you entered a number for the rabbit population, and another number for the fox population, and added a few variables (climate etc). Then the programme would show you how the different populations would rise and fall over time - more rabbits means more food for the foxes, so their numbers increase until all the rabbits have been eaten, at which point the foxes decline and the rabbits start to increase.
This happens all the time in the natural world, and humans are not immune to it. Over 1000s of years we will gradually overtake the available resources and we'll reduce our numbers, which will allow the natural world to replenish.
Trouble is, the timescales involved are vast - it might be another 10,000 yrs, but eventually an ice-age or disease pandemic will reduce the population of humans to a more managable number.
Then over many thousands of years, new species will emerge to replace the ones we destroyed.
From a geological point-of-view, we humans have only been around for a blink of an eye... as long as there is life somewhere on the planet, even if it's the last cockroach hiding under a rock in a nuclear winter, the planet will revive itself.
In primitive societies this cycle is much more rapid - infant mortality is very high, death from disease is much more common than in the western world, and (despite what Ray Mears etc suggest) hunter/gatherer societies are incredibly violent.
This means that slight variations in food availability, or a short inter-tribal war, can wipe out large percentages of a tribe, allowing the local fauna and flora to build their numbers back up.
Modern humans, however, have worked out how to control their environment which means we're much more resistant to that kind of pressure. It takes something really large - Black Death, asteroids, ice sheets etc - to cause problems, but they only come around infrequently (from our point-of-view).
It's also worth noting that in primitive societies deaths from war and violence run at about .5% - that's across all nations and climates, and includes pre-colonial societies - whereas in the West today it's less than 0.3%. To give some perspective, a death rate of 0.5% would mean that instead of the 90 million people who died in wars in the 20th Century, it would have been over 2 billion people. So in primitive societies this high death rate does a good job of keeping numbers down, but isn't a pleasant way to live your life!
Part of the reason there are so many humans today is that we are much less violent that 10,000 yrs ago... I know it doesn't seem like it, but the truth is that a baby born today in the Western world has the best life expectancy that anyone has ever had in history.
When you have infant mortality at 50%, and then add the massively increased risk of a violent death, plus disease and famine, it's not suprising that we used to live "in harmony" with nature. Nature had plenty of time to recover because humans were rubbish at living past their 30th birthdays
A return to aboriginal values would be nice in some ways, but the reality is that life as a hunter/gatherer is far removed from the rose-tinted view that Mr Mears gives... it's not quite the "
solitary, poor, nasty, brutish, and short" life that
Thomas Hobbes describes but in many ways it's not far off.
I guess my point is that given time things will sort themselves out - it's just that the timescales are so massive it's hard for us to grasp.