One point I'd like to have covered more thoroughly in the article is the notion that a horticultural alternative such as large scale permaculture-based food growing could simply replace agriculture. The text of a footnote to a previous blog post (see below) adds a worthwhile clarification:

On a large enough scale, even a major improvement such as permaculture would seem to suffer from a similar problem of transforming the land excessively for human consumption. It is intended, however, to be practiced on a scale small enough -- and with ethical constraints against large populations -- that it might prove sustainable under conditions of a much smaller human population. This is not to suggest it as an "alternative" to agriculture, without which humans did quite well for most of our history. As an approach to small-scale gardening -- something practiced by many hunter-gatherers -- it makes great sense. Once we begin to depend, though, on growing food as our primary means of subsistence, upping the scale by altering large tracts of habitat, taking control of our food supply by creating and storing unnecessary surpluses, the problems start. (I am aware of nothing concrete, by the way, built into the practice of permaculture which would prevent population growth. I welcome information to the contrary.)

That said, there will surely be a transitional period, post-civilization, when permaculture and related approaches to food production will be essential to many of those shifting toward true sustainability, even prior to a full move into hunting and gathering.

Related to the note above, please also see the more recent notes following the previous post.