Earlier quoted context omitted.
Perennial polyculture food forests reduces the advantage of high tech equipment. Nature does the work of growing. Replanting is rare. Harvesting is more of a manual process.
What are the yields like? What would doing that for all food do to the price of food?
But it seems unlikely to approach the yields of annual monoculture farming. (One quote: "The biggest difference, however, comes from considering perennial cereals. Most of the cereals that people eat (such as wheat, rice, oats, and corn/maize) are grown in annual plantings and often in monocultures. Since cereals account for at least half of dietary energy world-wide, converting that production to perennial polycultures with mixed intercropping would be a significant change in worldwide agriculture.") That's a bad thing; I'd like to see more use of these techniques, for all of the primary benefits mentioned in the paper. (The yield thing for subsistence farmers is a secondary benefit.)
[1] And it would help if I added the link: http://www.rand.org/content/dam/rand/pubs/occasional_papers/... [PDF]