It depends on how you define "natural". Is anything that happens in real life "unnatural"? Didn't it come about through "natural" biological desires, created by evolution? As long as you don't believe in God, anyway.
So you have to define some dividing line, or at least a scale, telling when humans exercising their "natural" intelligence leads to "unnatural" results.
I don't know if I'm disagreeing with you or not. It's just a tricky idea that needs to be defined.
Toxic waste is a perfectly natural by-product of our industrial processes. (You could argue those are natural too). Similarly, introducing these wastes into the air and ocean also leads to natural consequences.
I think the issue is that people confuse "natural" with "able to sustain human life". The planet Mercury is perfectly natural, but humans can't live there. In the same vein, we can do lots of natural things and our environment will find a way to balance things out.
Where I feel people are short-sighted is that eventually that ecological balancing act precludes the existence of human beings in this planet.
I was trying to illustrate how pointless the "natural vs unnatural" argument is. If we were truly concerned with only doing things naturally then we would be living in hunter gatherer groups and not living past 18. Farming wouldn't be allowed, as that's just as unnatural as any other extension of our tool use.
I can't see how tool use is unnatural by any definition. We do it without any prompting, as do chimps and even some birds. Ours are just more complicated. Living past 18 is a natural result of having enough food to eat and relative safety, again deriving from our natural intelligence.
My point is that it's an uphill battle to declare any given real phenomenon as unnatural at all.
So you have to define some dividing line, or at least a scale, telling when humans exercising their "natural" intelligence leads to "unnatural" results.
I don't know if I'm disagreeing with you or not. It's just a tricky idea that needs to be defined.