In forestry, we see the interaction of human, social-economic systems with eco-systems. Sustainable forestry should have as its aim the cultivation of ecosystems to ensure that they remain productive. Measurements of productivity must take into account all forest resources - both the tangible ones such as foods, seeds and timber and also the intangible, functional ones such as the transfer of energy and nutrients.
Our limited understanding of the human interaction in the dynamic processes involved in ecosystems forces us to simplify these interactions. In an effort to quantify productivity, it has been simplified into terms such as 'biomass', or worse, 'timber yield'. Forestry practices based on these simplifications thus tends to lower total forest productivity despite the fact that timber yields may remain sustainable.
Classic ecology teaches us that the productivity of an ecosystem is the rate at which it harnesses solar energy, through photosynthesis. A certain proportion of this productive output is invested in the respiratory processes of plants. The remainder is what is called 'primary production'. It consists of that portion of photosynthesised energy that is converted directly to biomass and, theoretically, can be measured in units such as 'kilograms per hectare per year'.
In practice, measuring primary production is difficult, if not impossible. It must include not only above-ground biomass, such as stem and leaf growth, but also below-ground biomass, such as tree roots. The latter possibly comprises at least half of the total primary productive output of the forest.
All secondary production, ie., all non-photosynthesising organisms, including humans, are dependent on primary production. Some of this secondary production is biomass and is available as food for predators or parasites, or provides nutrients for plants. The remainder of the secondary production is spent on movement and the general life processes. These are integral to the productive process and hence should be considered in the productivity equation. For instance, they assist in the dispersal of seeds, facilitate the aeration and conditioning of soils as well as performing myriad ecological functions.
Measuring productivity in units such as kg/ha/year says nothing about all productive elements that are not in the form of physical biomass. It ignores fluxes of energy and the high degree of order in truly productive ecosystems. The biomass production and the value or 'quality' of an ecosystem are not the same thing. Some of the most destructive ecosystems (eg, algal blooms) are the most 'productive' in biomass terms. Similarly, many Old Growth Forests are considered by classic forestry to be 'unproductive'.
A more useful quantity is productive efficiency. This is a measure of how well an ecosystem cycles available energy and nutrients. Each site has a variable potential for energy and nutrient extraction and this determines its productive potential. Efficiency is how close real production comes to its potential.
If energy or nutrients are removed from the system or placed in such a form that they become unavailable for recyling, then productive efficiency is lowered. Unfortunately, this is exactly what conventional forestry does.
For productive efficiency to be a meaningful concept, it must not only include how efficient the forest is at recycling energy and nutrients but also the degree of adaptiveness, what stage of succession, diversity (ie, how many productive pathways) and how all these efficient ecosystems would consist of a large number of highly interdependent and specialised elements in the climax phase of succession. Each element of such an ecosystem is exquisitely adapted to harvest a very specific set of resources. All niches are filled and energy and nutrients are cycled with maximum efficiency.
Humans, in their distorted economic realities, seem ignorant of this, removing nutrients and energy and placing them in a form that is not available for re-assimilation by primary production. This substantially lowers the productive efficiency of ecosystems.
Forestry should seek to achieve the integration of the human element so that it fulfils the productive requirements of the ecosystem. In a healthy ecosystem, each element should maximise productive efficiency. The human interaction, as an element of secondary production, should seek to redirect resources back into primary production. This means a substantial effort should be directed at reafforestation, and careful harvest of forest resources.
Truly sustainable forestry can only come from an intimate understanding and appreciation of forest ecosystems. This is not simply obtained by scientific evaluation and quantification. It must also incorporate an instinctive 'sense of place', and comprehension of qualities derived from knowledge that human and forest ecosystems are intertwined. We must acknowledge the social and spiritual functions provided by healthy ecosytems and understand how these energies can be directed toward the massive task of restoring degraded areas. Educating and enlightening people to the potential of sustainable forestry will co-exist with the delight and personal satisfaction people achieve through its practice.
1. See under Forest Activist Groups, in the Directory.