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.