Analog Forestry is a system of forest management that seeks to establish a tree-dominated ecosystem that is analogous in architectural structure and ecological function to the original climax or sub climax vegetation community.
We use 12 principles to orient our design strategies and help guide us towards solutions that maximize ecological, human benefits. The principles of Analog Forestry are:
The mature ecosystem of any area represents the outcome of eons of experience in dealing with the climate and impacts at that place. Seek out and observe the most mature native forest in your area. If something remains, though in a degraded condition, it is still useful, there will be many lessons to be learnt. If nothing remains, look to history, books, stories, and local experience build up an idea of what the land once sustained. Observe the ecosystems and the patterns of biodiversity in the area to be treated.
Record the species and ecosystems present in the area under treatment. The initial data will assist in setting a baseline against which future observations their changes can be evaluated. Recording is also of importance in evaluating the management activity and in maintaining a management history.
It is important to record the physiognomic formula for the vegetation types on the land. The structure of the system will demonstrate a wide range of different architectural responses. The provision of a suitable structure is addressed via the growth habit of the species being evaluated for use.
Understand the ecosystem being observed from as many perspectives as possible. It will function in one way for the ornithological element, another for the herpetological element another for the hydrological performance and yet another for its social and economic performance. The ecosystem will have certain physiognomic features and taxonomic features. A synthesis of many variables will always yield better choices of the species and patterns to be used in design. This is when the observations and records must be synthesised with as much scientific and traditional information as possible.
The creation of a database on the vegetation species that are (were) present in the area and the potential new species to be considered is a critical part of recording and should be initiated at the inception of the project.
A very potent tool in appreciating the function of the ecosystem is construction of the vegetation database. This enables an assessment of both ecological function and anthropocentric function, which include economic, social or cultural value provided by a single species or by the community as a whole. The performance of each member of the vegetation complex impacts the stability of the ecosystem. For example, a soil building species might contribute to its stability positively, while an invasive species might contribute negatively.
Once an understanding of the components of the ecosystem in question is gained, it is possible to evaluate the species within it in terms of the management goals.
The better a manager understands his or her land the better will be the management response. A good understanding of the geography of the land, its peculiarities and its history is important prior to design. A powerful tool, in understanding the land is a carefully drawn out map that identifies its most pertinent features. Mapping the land is best done if developed as a series of overlays. Once the physical boundaries have been mapped, overlays that demarcate the contours, the hedges, fence lines, vegetation, soils, wind direction and water flow are some useful variables.
Know the land in terms of its soil condition and biodiversity. The soil ecosystem is probably the most important asset of a farm. The soil, like trees, crops or livestock upon it are constantly changing, living thing. All we have to do is occasionally turn the soil with a spade to be impressed by this fact.
Identify the different economic outputs possible as a consequence of the design. All of such products will have an optimum level of extraction. The awareness of optimum yield level of each resource and designing for sustainable production will assist in setting the levels of yield and determining design.
Design decisions as well as management decisions, will ultimately be based on goals and outputs that facilitate the achievement of such goals. A good knowledge of the levels of yield both in terms of individual species and ecosystem services is important.
The yield required will differ depending on the priorities of the landowner or manager. If the goal is conservation the yield will be measured by increases in the target species, if the goal is economic gain the yield will be measured in terms of income or production. If the demand for yield is focussed on a single crop the higher the yield required the more the production system would move towards a single species monoculture.
Finally, the levels of yield should correspond to the value set on different aspects of the design by the operator. For instance one operator might look for bird and butterfly increase as yield because ecotourism is seen as the income source, while another operator might look for high value market crop production because traditional agriculture is seen as the income source.
Every landscape has flow systems, where solids, liquids, gases, and genetic materials produce distinct patterns. Usually the direction of flow in solids, liquids and gasses is governed by gravity, resulting in the very characteristic drainage patters of water or soil flowing on land. Similarly wind moving across the landscape produces some significant patterns. Genes, for their part, usually follow existing corridors of ecosystems conducive for that species.
The understanding of the flow systems across the farm or land area to be managed is important to setting the design. Cutting across flow systems is usually not productive. Following, augmenting or ameliorating flow systems to improve the ecosystem being designed, such that the crop or organism under management, will improve productivity.
The other consideration in looking at flow systems across a landscape is the propensity to form reservoirs. In water-flow systems, reservoirs, be it natural or artificial can contribute greatly to local productivity. A similar relationship can be seen in the soil, with mineral soils weathering and flowing to form reservoirs of concentrate and in the flow of the organic fraction of the soil.
Heterogeneity, or a difference between various landscape elements, is a fundamental cause of species movements and material flows. The distribution of species and the condition of landscape structure are linked in a feedback loop so that the expansion and contraction of species among landscape elements has a major effect on, as well as being controlled by, landscape heterogeneity.
As spatial heterogeneity increases so does the potential for energy flow across ecosystem boundaries. As the number of individual ecosystems increase within a landscape, a greater proportion of edge animals and plants move between adjacent systems. Thus, as landscape heterogeneity increases so do the flows of heat energy, nutrients and biomass across the boundaries separating the various elements.
Mineral nutrients flow in and out of a landscape. Their residence time within an ecosystem is governed by the dynamics of wind, water and organisms. Most ecosystems have well developed regulatory mechanisms to hold their requirement of nutrient within that system. Disturbance however, especially when severe, disrupts these mechanisms and facilitates transport to adjacent or other ecosystems. Therefore the rate of redistribution of mineral nutrients among landscape elements increases with the intensity of disturbance within them.
All ecosystems use energy to maintain their identity. In agricultural ecosystems, productivity is a goal and energy is expended in order to meet this goal. Often energy subsidies from outside the farm have to be provided. As an increase in the flow of energy tends to organize and simplify the system, increases in external energy inputs impact both biodiversity and sustainability. Increases of energy to an ecosystem represent a measure by which ecosystem modification can be addressed.
Increases in the input of energy to an ecosystem, tends to organize and simplify that ecosystem and change its biodiversity, the removal of that input will lead to a collapse of the system. The greater the modification
of the system, the greater it depends on external inputs. Thus energy dependency can provide a measure by which ecosystem modification can be addressed. In a heavily energy dependent agricultural system, the natural or biological system has been dispensed with and an artificial environment has been created to allow for increased production. Such a system is not only unsustainable; it creates a dependency cycle that the operator will find difficult to break out of.
The example above illustrates the need to identify baseline descriptors that can be considered as ground states or thresholds from which a measure of sustainability or non-sustainability can be described. For instance, if a process uses a certain amount of inputs to maintain its identity, it can be described relative to that level of inputs identified as the baseline. Any change in state that requires a change in the amount of inputs required to maintain its stability and productivity can then be evaluated as to its potential for sustainability. If a process uses x inputs to maintain its identity and if this process can maintain itself by securing these from its environment, it can be termed a sustainable process. Now the same process can be accelerated or expanded by adding y inputs. This process, while still maintaining its identity, has increased in some manner but now requires a constant input of x + y to maintain this state. The removal of the extra inputs could lead to the process degrading to a state different to the original ground state.
All farming land will be a part of a natural landscape. The boundaries of which are often set by definition. A common criterion to delineate a landscape is on a watershed basis. Once identified, each landscape can be divided into various replicating, such as open fields, tree covered, homesteads, roads, streams etc. A landscape will often have many vegetation components ranging from mature native vegetation to open meadows. The patches of remnant vegetation often being the only habitat left for native biodiversity.
The connection of these habitat patches with corridors will reduce the populations’ vulnerability to extinction. Small isolated populations are particularly threatened with extinction due to ongoing deterministic factors and greater influence of stochastic processes. I -t is the stochasticity inherent in small populations (e.g. the chance that all offspring born in one season are male) that will ultimately lead to its extinction. Corridors can increase the effective size of the habitat patch and lessen the chance of local extinction. The more analogous to the original, the more effective the corridor. Another possibility is to increase patch size by creating an outwardly expanding zone of vegetation analogous to the original ecosystem
When considering a landscape we must also consider the effects of scale, as we extend or reduce scale from a certain perspective, certain elements will change, in the same manner as the change of vision wrought by focussing a lens. Some elements will gain importance at the new settings while others lose importance. For instance when looking at a flatweed that is the crucial element-providing habitat for a certain species of millipede, the plant is the most important consideration of the ecosystem. But if the scale of the ecosystem is increased the flatweed goes out of focus and becomes one with the grassland. At this scale it is the occurrence of patches of flatweed in time and space that is seen to be important to considerations of the millipede. On further expansion of scale the grassland is now seen as a patch in a forest, so the occurrence of the grassland in time and space becomes the important consideration. The landscape perspective has changed radically, so that retaining meaning relative to the object of concern, requires the information to be retained by encoding or otherwise including the information into some element of design within the planning process. For example, defining the species of tree to be used in a re-vegetation context ensures that the species chosen will be a food source for another group of organisms not addressed in the re- vegetation needs. A similar recognition of the value of hierarchical structuring using abiotic, biotic and cultural subsystems has provided a planning framework for urban planners and developers in the urban ecosystem.
In the development of a forest system maturity brings changes in the trophic web which are demonstrated by changes in species composition. This trend is illustrated by studies of the distribution of mammals in the forests of western Oregon by Harris et al (1982). The forest was studied as a sequence of six successional stages and terrestrial vertebrate species were studies at each stage. These successional series all maintain about an equal level of species at each level, but the composition of the species represented changes with the change in vegetation.
The tree species that are characteristic of each stage confer stability to that particular stage, thus mid-seral successional stages are often better adopted as design criteria for woodlots, orchards, home gardens, tree farms or agroforests. Early successional stages are mimicked by annual agriculture and pasture. Incorporation of ecological processes that contribute to further stability, can thus lend a great deal to design. In the tropics, the use of mid-seral leguminous trees such as Erythrina, Gliricidia, and Inga as shade trees for tea, coffee and is common. As the crop plants are shade adapted mid seral plants which do best in a microclimate created by light shade, the use of shade trees is important to achieve optimum production. In this design it is clear that the species of shade tree above the crop plant can change in composition but not in structure. That particular seral analogue is the best design that has been found for the production of perennial crops like tea, cocoa, coffee etc.
The structure of this system means that crop trees up to 2 m in height are protected by shade trees at about 7-10 m. The crops are the same in each country but the species used as shade trees are often very different. For instance, Erythrina (flower pictured) is used for shading coffee in India, while in Central America Inga is the common shade tree for coffee, while growers in Papua New Guinea use Casuarina and Leucaena is the popular shade tree in the Philippines. Sometimes, this structure is developed into a more mature ecosystem by adding larger trees such as Albizzia or Michelia
The early seral stages such as grasslands, herb fields, meadow etc. have their particular seral analogues; these are the systems of annual cropping or pasture. The ecological characteristics of the early seral stages are r selected life strategies, that is plants that are short lived, low root/shoot ratios, produce many seeds, etc. While it is possible to enable many such ecosystems to develop into more mature states, the relative advantages of changing this land to forest type ecosystems has to be carefully considered.
In designing for structure, the seral stage that is best suited for the crops chosen provides the model. Thus, if the crops in question are annuals, such as cereal grain, beans, squashes etc. the pioneer stages provide the model. If the crops in question are perennials such as coffee, fruit etc, the later seral stages provide the model. The pioneer stages in most ecosystems are diverse and incorporate a range of plant types capable of high productivity, a pattern often reflected in traditional agriculture. The early seral stages of forest ecosystems, provide the next growth or building up phase.
Incorporation of ecological processes into design always contributes to further stability. All ecosystems are driven by a series of processes some of which are important and contribute to maintaining stability and productivity. Ecological processes in every ecosystem, allow for increases in efficiency through management.
The identification of key processes such as edge effects, where the ecotone or the boundary between two ecosystems facilitates a higher biodiversity. Keystone species: a species on which the persistence of a large number of other species on the ecosystem depends and whose impacts are greater than would be expected from its relative abundance or total biomass or the use of indicator species, organisms that correspond to a certain level or state of biodiversity, will enable the design of an effective and elegant model.
Biodiversity has been perceived in many ways over the ages. It is pattern wrought in biomass at any time. It provides the variety of our living world and has been the source of human inspiration across cultures and ages. Biodiversity provides the material as well as the indicators for sustainable land management. In modern times it is invaluable as a management tool as the level of biodiversity is an extremely useful measure of the health of ecosystems. Biodiversity measures have also been correlated with environmental stability. Similar patterns have been found in studies of the sustainability of agricultural and forestry practice. Thus, the integration of biodiversity needs into laws and policies governing natural resource based production systems is essential for management towards a higher degree of stability and sustainability.
The pattern of increasing ecological stability with increasing diversity in land use is also corroborated by studies of traditional land managers, whose management systems are sustainable and conserve a much higher level of biodiversity than conventional responses (Altieri et al 1987). High levels of diversity in the agricultural field produce positive effects of biological control, spread the risk in marketing and production, as well as distributing labour needs to fit with a single family unit (Conway1987). These traditional methods of land management have much to contribute to biodiversity management.
These approaches to the measurement of biodiversity can yield methodologies that can be used to set value on various types to land management. However, it is also useful to stop and reflect that humanity did not always perceive biodiversity in this analytical manner. Consider the sentiments of an indigenous leader:
Our ways are different to your ways. The sight of your cities pains the eyes of the red man. But perhaps it is because the red man is a savage and does not understand.
There is no quiet place in the white man’s cities. No place to hear the unfurling of leaves in the spring or the rustle of insects wings. But perhaps it is because I am a savage and I do not understand. The clatter only seems to insult the ears. And what is there to life, if a man cannot hear the lonely cry of the whip-poor-will or the arguments of the frogs around a pond at night? I am a red man and do not understand. The Indian prefers the soft sound of the wind darting over the face of a pond, and the smell of the wind itself, cleansed by a midday rain, or scented with the pinion pine.
Until modern society recognizes the fact that there are values other than monetary, there will be a need for ‘objective measurement’ to set value. To obtain some universally agreed measurement of biodiversity is an important international goal. Such an agreement can allow the linking of biodiversity measures to development funding. While it is imperative that the momentum gained for conserving the remaining fragments of natural biodiversity not be lost, it is also crucial that biodiversity concerns be recognized by macro policy. As an expressed objective of the Global Biodiversity Strategy is, ‘to integrate biodiversity conservation into international economic policy’ (Anon 1992) both measurement and evaluation of biodiversity must be addressed as a matter of priority.
It is an issue today, because that human inspiration cannot be appreciated by a non-human system. The beauty and wonder of the living world cannot have meaning in the marketplace. As a consequence, this value of biodiversity has retreated before the onslaught of the monocultures of economic expediency.
Maturity is the end condition all ecosystems tend to develop towards. It represents the ability to stay sustainable in a given geographical site. Seral succession or the gradual changing of species and structures in an ecosystem as it moves towards maturity is a singularly important consideration in design. Maturity is a process more than an end condition. Mature ecosystems are usually higher in biomass, though not necessarily in biodiversity than more immature systems. As maturity confers stability every element of a landscape that can mature should be encouraged to do so. The term climax is often used to denote the end state of seral succession in tree-dominated ecosystems.
In the end, every artist has to use the palette at hand. The database may be incomplete, the maps may be poor. Often, data on the region may be lacking, familiarity with landscapes or ecosystems are often superior to poor data. Every landscape and its associated ecosystems will have unique characteristics, some a level significant for design, others not. Every landscape, every ecosystem has nestled within it many more. Management and monitoring has to proceed on an agreed scale. Responding to change on the landscape must be biased towards system biodiversity rather than time based action. All this requires the designer to respond skillfully and creatively.