"Don’t think you are on the right track just because it is a well beaten path"
Commentary by Tim Sonder, Edible Evanston (November, 2019)
The interface between things is where the most interesting events take place. These are often the most valuable, diverse and productive elements in the system.
Think of the ocean, and then look at tide pools and marshes. Where do you see a greater diversity and density of life? Look at a forest, and then study the area where it transitions to meadow or lake or stream, and you will, once again, find a greater diversity.
All exchanges happen at edges, and exchanges lead to an increase in value: The place where two eco-systems or habitats meet is generally more productive and richer in the variety of species present than either habitat on its own. In ecology this is called 'ecotone.' This is central to the idea of using edges as a design method. The logic is simple. If the most productive bit of woodland is the edge, then design it to have a bigger edge.
These ideas are used in alley cropping, shelterbelts and pond design.
The permaculture designer, in planning for ‘more edge’ in a given system, works to increase ‘overlap’ between ecosystems, thereby creating more biodiversity. The more ecosystem edges that meet, the better. Paths create edges and serpentine paths provide more edge than arrow-straight paths. By clustering trees and leaving open spaces, one can simulate the forest edge effect. Beneficial and less desirable critters use the margins—deer paths, pollinator flyways, human walkways—and seek shelter at the edges. More diversity.
Look at other interfaces: Soil/air, soil/water, water/air. Urban/suburban/rural. House/garden. Grass/bed. Sidewalk/grass. Rail tracks and the right-of-way. The walls of our cells. Our skin and the air.
These fertile areas frequently have their own microclimate created by an exchange of heat, or moisture or by a sheltering effect. Sometimes gentle, sometimes harsh, but different than the surrounding mass and therefore increasing diversity. Weeds, the pioneer species we deal with regularly, thrive in disturbed and challenging environments with lower competition. Sometimes unwanted, they are certainly part of diversity.
Valuing the marginal can be seen in several ways, including from a societal or intellectual standpoint: ideas, views, unusual plants, wild animals or people at the 'edge' of society. The paradigm-changing ideas in society are often generated by those who are marginalized, at the edge of acceptable norms.
And back to weeds: Eating what is considered a weed is seen as non-conforming behavior, but it also can provide extremely high nutritional value.