I have just read the book “Eating and Healing: Traditional Food as Medicine”. Andrea Pieroni and Lisa Leimar Price, editors, 2006. Haworth Press.
 
The book has 16 chapters and examines the role of wild food plants in various indigenous communities in different parts of the world. Most importantly it gives some general findings that are cross-cultural, in other words applies to indigenous communities worldwide.  The book verifies many of my thoughts developed over the years on this topic.  I highly recommend the book to anyone interested in this broad topic.
 
Several take-way points for me are:
 
1) Wild food plants are widely gathered and consumed by indigenous agricultural cultures as well as by hunter-gatherers.
 
2) Many of these wild foods are rich in medicinal substances as well.
 
3) Wild foods are important contributors to the nutritional health of those who consume them, particularly women and children.
 
4) Many of these wild foods are found as weeds in agricultural fields, fallow fields or village surroundings. Some are native but many are non-native.
 
5) As the wild foods become scarce, they are increasingly protected and/or brought into cultivation or semi-cultivation by the gatherers, primarily women.
 
6) The erosion of the traditional knowledge of these wild food plants is increasingly documented around the world as more indigenous cultures are brought into the cash economy and purchase foodstuffs from the global pipeline.
 
The findings of this book are very much in line with the interface between permaculture, ethnobotany and ecosystem restoration which I have been writing and lecturing on for many years. Permaculture plantings and ecosystem management very much should include the planting, protection and increasing of these wild food species so that they are abundant in the landscape and so that less of an overall area has to be in agricultural ecosystems. We should really work hard at making wild food plants abundant in the landscape.  Native edibles and medicinal plants (many plants are both) should be incorporated into permaculture assemblages. In other words, agricultural systems should become more biodiverse, wilder and require less management. Non-native plants should be thoroughly investigated for their uses. Some invasives can be selectively harvested for home use or marketing and thus reduce them in the landscape in preference to native plants.  Harvesting of non-native useful plants can be done in conjunction with planting of native plants to tilt disturbed ecosystems more in favor of native plants. These related topics are always something I discuss in my permaculture design courses.