Diversity is the term used to describe a rich, interrelated mix of elements. The key concept is that the elements are usefully related in some manner. The quantity of elements is not nearly so important as the number of connections between them.

A comparison of two types of tree-growing situations may serve as an example of diversity -- a Christmas Tree farm and an old growth forest. In the Christmas Tree farm, diversity is low. The trees are all of the same age and species, spaced an equal distance apart, and trimmed to be a uniform shape and height. The ground surface is maintained in grasses and periodically mowed. Fertilizers are added to supplement soil nutrients. There is little habitat for wildlife. Tree plantations for pulp, poles and construction wood share these characteristics. In the old growth forest, diversity is high. The trees are of varying age and species; they are spaced in a random pattern; they have a variety of shapes and heights. The ground is littered with logs and fallen branches and sustains a full ecosystem of herbaceous plants, mosses and ferns. In the many layers of forest from the top of the trees to beneath the ground there is an abundance of wildlife. The forest has a full range of trees from tiny seedlings to dying giants and the decaying snags of those long gone. The old growth forest has many more opportunities for meaningful connections.

The value of diversity lies in its complexity, most of which we don't have the ability to understand. This diversity allows the landscape to maintain itself and be resilient to change. While organisms may be complete, independent and autonomous, they are dependent on other life forms. In may regards an ecosystem is not just a collection of creatures but because of mixed relationships is, in itself, an organism. (Nancy Jack Todd and John Todd, From Eco-Cities to Living Machines, pg. 26-26). Diversity of organisms and connections sustain the larger ecosystem for the benefit of all.

A current issue is maintenance of genetic diversity. With our recently found ability to manipulate genetic structure we introduce new characteristics into organisms while removing those that have evolved over time. Species extinction also leads to loss of the gene pool. Reducing and simplifying genetic diversity is considered by some to be a dangerous trend. Chris Maser (Restoration Forestry, 1988, pg. 90) sees three problems in the maintenance of a stable forest. Manipulating genetic structure: 1) produces lack of predictability; no one has yet grown a 'genetically improved' forest for even one rotation; 2) alters the function of ecologic processes in the individual trees and the forest; since we don't know all the functions we don't know what the long term impact will be; and, 3) gives up genetic flexibility making the forest less able to adapt to changes in climate, pollution and other stresses. Plants and seeds we use in the future may well be from native stock that has had its genes changed and its name patented.

On the practical level, our gardens will not have the diversity of a fully functioning natural landscape. The more of a monoculture it is the less diversity it will have. Robert Koruik (Lettuce Consider the State of the Garden, in Solar Living Source Book, pg. 466) says it this way: "Most gardens have plenty of room for more well-chosen diversity, which may enrich the biological atmosphere and the environmental dynamics for a more self-modulating garden. Such gardens are perhaps more natural, but still a far cry from actual native ecosystems."

Mollison and Slay (Introduction to Permaculture, pg. 25) point out that "the importance of diversity is not so much in the number of elements in a system; rather it is the number of functional connections between these elements. It is not the number of things, but the number of ways in which things work." "Diversity is often related to stability in permaculture. However, stability only occurs among cooperative species, or species that do each other no harm. It is not enough to simply place as many plants and animals as you can into a system, as they may compete with each other for light, nutrients, and water."

We seek to provide a collection of plants, animals and structures that work harmoniously together. Guilds, or companion plantings, are a close association of species clustered around a central element. Plants support each other by reducing root competition from invasive grasses, providing shelter and nutrients and assisting in pest control. Lists of companion plants are readily available in publications on gardening.