In order for your argument to hold, I feel like you would also have to say that farming anything is inconsistent with
permaculture. So, no
chickens,
rabbits, cows, pigs, etc. Further, I would even argue that farming plants in beds or even in a specific area would be inconsistent according to your principles. Even more so, I think that changing the landscape to favor
water properties that you desire could also be thought of unnatural.
So, I think I'll take this stance:
Permaculture is the understanding and utilization of natural processes in a way that is beneficial to mankind, while also being
sustainable for the earth.
By that definition, I would say that a worm bin is taking a natural process and using it to its fullest potential in the effort of being beneficial to mankind. If you've ever kept a worm bin, you will also see that the worm population is naturally governed as well. When there is too much food and living conditions are favorable, there are more worms. When there is too little space and worms are cramped, they slow down reproduction. In that way, nature balances itself.
Currently, I have taken my worm farm and dumped it into a banana circle that I use for composting. That allows there to be a ready supply of worms and I try to keep it suitable for them as best I can. If the pile doesn't get too hot, then they stay there. I also find that I get multiple types of worms too. So, that is cool.
As far as my garden... There are MANY things that are not natural. However, I am using principles of nature to create environments so that it is self-sustaining. My banana circle has the input of my wastes and then turns that into great
compost / additives for the garden. I pull weeds from the garden to throw into compost. I add the compost onto the garden plots. I add seed to the plots where I want them. I harvest fruit and veg from the garden plots. I collect rain water and distribute it where I want it to increase yield. There are MANY ways I bastardize nature in the interest of a permaculture type environment.
If you want to create a culture of people that can be permanently sustained, then I think we as a whole
should be working together to learn and to teach as much as we can about the natural processes in their simplest forms (like a worm bin) so that the world as a whole can survive and thrive with us still here.
Just my thoughts on things.