3. Notes on the analysis and evaluation of environmental impacts

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All action in the forestry sector is based on the principle of sustainability. This requires a form of utilisation which is in line with the potential of the natural resources and which preserves both the steady state of the natural cycling systems and the ecosystems' capacity for self-regulation (VESTER). Sustainability thus does not imply a constant annual yield level - in timber production, for example - but rather the achievement of goals such as ensuring species-rich natural regeneration through the use of resource-conserving timber-harvesting methods (SEYDACK et al. 1990).

As intervention by man disrupts these cycles, it is essential to use not only sustainability indicators such as annual cut but also ecological and socio-economic indicators:

· Nutrient balance

Nutrient cycles are a function of stand density, soil exchange capacity, nutrient storage and allochthonous introduction of substances via the atmosphere. As it is virtually impossible to control exchange capacity, storage and introduction of substances, management concepts must aim to minimise nutrient losses. If use of mineral fertilisers is to be avoided (since they generally necessitate use of non-renewable energy sources), nutrient losses can be offset by means of allochthonous introduction of substances only where small quantities of stem timber are removed over long production periods. Nutrient-deficient sites severely restrict production of large timber and biomass (see GOLLEY, RUHIYAT 1989 in WEIDELT 1989, ULRICH). Relevant indicators are

- nutrient reserves in kg/ha, broken down according to ecological compartments such as soil, roots, stem timber, branches and foliage, and
- nutrient flows between the individual compartments in kg/ha/a, including introduction and removal of substances.

· Water balance

Water is a limiting factor in many habitats. Its availability varies according to hydrogeological and bioclimatic conditions. As these components of the natural environment cannot be changed, the intensity of utilisation must be geared to the dynamics of the water balance in individual catchment areas. Near-natural storeyed forests are most capable of controlling the water balance. The components of the water balance - i.e. interception, evapotranspiration, run-off and groundwater recharge - can be controlled by means of forest tending and species selection (cf. MITSCHERLICH, WENGER). Depending on purpose, individual components can be used as sustainability indicators, for example to quantify groundwater recharge in arid regions.

· Soil erosion

Soil erosion is essentially a function of stocking, precipitation and relief intensity. It forms part of the Earth's natural cycling system. The smallest degree of soil erosion occurs under species-rich, storeyed high forests. The indicator for soil erosion is

- the site-specific geological norm (kg/ha/a), which can be ascertained on ecologically undisturbed sites by means of simple field trials (e.g. FAO) or, if this is impossible in totally degraded regions,
- the tolerable soil loss threshold, which can be ascertained by empirical means with the aid of the general soil loss equation after WISCHMEIER (e.g. in MORGAN).

Both of these indicators provide a criterion for the intensity of utilisation and the technical and biological protective measures required.

· Forest area

The minimum amount of forestry land required is determined by the population's requirements in terms of forest products and the economically necessary protective functions. The amount of land required depends on site-specific factors and the habits of the local people. In addition to ecological criteria, wood requirements and wood consumption must be taken into account along with the degree of fragmentation (ELLENBERG, PIELOU) of formerly continuous forest areas. One indicator is the forest area balance, expressed (in hectares) as the difference between the existing forest area and that which is economically necessary.

In the event of changes in the intensity of forest utilisation it is essential to know the parameters serving as a kind of early warning system which make it possible to spot new problems as soon as they start to develop. Apart from the ecological indicators mentioned above, such indicators may also be biological (pioneer plants, particular types of animal as anthropophilous species) or socio-economic (increased market supply of gathered products hitherto used only locally).

Economic assessment of forest resources involves various factors of uncertainty. Conventional monetary methods do not adequately cover the forest's indirect functions or the non-timber products generated "informally" to meet the population's own requirements. Cost-effectiveness and risk-analysis methods must therefore be used for evaluations in the forestry sector (BMZ, EWERS, KASBERGER-SANFTL).


4. Interaction with other sectors

Against the background of population growth and steady depletion of resources, it becomes clear that the core problem in the forestry sector, namely destruction of the forests in pursuit of economic interests, cannot be solved by technical means alone. Back-up measures in related sectors play a crucial part in permitting interdisciplinary management of general conditions for the purpose of preserving human habitats.

4.1 Complementarity

Conflicts over use of resources can be avoided by ensuring that the individual sector plans complement one another. To achieve this, it is essential to raise decision-makers' awareness of the relevant issues. Implementation of comprehensive development approaches is restricted by politico-economic realities (national and international corruption, international trade agreements, function of timber exports as a source of foreign exchange for non-diversified economies). Integrated approaches employ tools such as the following:

- population policy, for limiting population growth and mobilising young people as a potential labour force
- economic policy, for conserving natural resources by limiting demand and reducing debt
- regional planning, e.g. for implementing large-scale afforestation programmes as a means of rehabilitating the environment and alleviating poverty
- energy policy, for conserving natural resources by enhancing efficiency and promoting the use of non-biological, renewable energy sources (solar power, water power, wind etc.)
- agricultural policy, for achieving food security through land reforms, raising of productivity and refrainment from large-scale resettlement programmes

The environmental briefs on related sectors can be consulted where necessary. Among those of particular relevance are the following:

For biological production

- Agriculture

· Plant Production and Plant Protection
· Livestock Farming

- Infrastructure

· Spatial and Regional Planning
· Overall Energy Planning
· Water Framework Planning
· Mining and Energy
· Renewable Sources of Energy
For harvesting techniques

- Agriculture

· Agricultural Engineering

- Infrastructure

· Road Building and Maintenance

- Trade and Industry

· Timber, Sawmills, Wood Processing and Wood Products

4.2 Social environment

Socio-cultural factors play a major role in determining the success of measures in the forestry sector. Apart from acceptance, the following factors are among the most important:

- traditional forest utilisation rights and obligations
- system of social controls regulating resource utilisation
- target group's income situation
- health and food supply
- training

The complexity of the social environment means that difficulties are liable to be encountered in recording sociological data. Techniques such as rapid rural appraisals (CHAMBERS) may prove useful for small-scale projects but are generally inadequate for integrated approaches.


5. Summary assessment of environmental relevance

Characteristic features of the forestry sector are the extremely long production periods and the large areas needed to permit regulation of key global cycling systems. The impacts of management errors are thus difficult to limit in terms of both time and area, as the consequences of choosing the wrong species of tree may not become apparent until more than a century has passed.

To ensure the success of forestry measures, it is thus essential to simulate natural cycling processes. Involving the local population in the forestry production process plays an important role as a social management tool, particularly in marginal living environments threatened with destruction.

The concepts for forest utilisation must therefore be multifunctional and needs-oriented. Monotypic plantations may thus prove site-appropriate under certain conditions, for example to provide a fuelwood supply in arid regions. In general, however, integrated management goals can be achieved only in near-natural mixed forests. Negative impacts on the environment can be minimised by employing techniques which refrain from measures along the lines of clear-cutting and contribute to creating and preserving heterogeneous stands.


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Annex: Glossary of selected terms

Basal area: Total of the trunk cross-sections of all trees in a stand exceeding a minimum diameter, given in square metres per hectare and serving as a measure of the stand density.

Biocybernetics: Subdiscipline of cybernetics (from the Greek "kybernetes", meaning "helmsman"), which describes the control and automatic regulation of interlinked, closed-loop processes with minimum energy input in biological systems

Biomass utilisation: In forestry, limited to timber utilisation in the form of full trees, i.e. stem timber including bark, leaves and branches, or whole trees, i.e. full trees plus root wood.

Biotope: The habitat occupied by an organism or community (biocoenosis) within an ecosystem, determined by physical and chemical factors

Compartment: Permanent physical unit of forest division, serving simultaneously as a unit for planning, execution and monitoring of measures .

Cost-effectiveness analysis: Comparison of operational alternatives in which the inputs are of a monetary nature but the outputs cannot be measured in monetary terms.

Ecosystem: A unit within the natural environment, consisting of a community and its habitat (biotope) and characterised by balanced cycling systems, i.e. dynamic steady states.

Management goal: Production goal for forestry operations setting out the range and order of precedence of all requirements on the part of the forest owner and/or the general public, both material (timber, non-timber products) and intangible (soil and water conservation, nature conservation, recreation). Distinctions are made between product goals, security goals and monetary goals, with times being set for their achievement.

Management goal type: Management goal for a stand or compartment.

Savannah: Form of vegetation found in the semi-humid tropics, generally between the inner humid tropics and the latitudes marking the Tropics of Cancer and Capricorn, consisting of grassland with scattered trees and shrubs.

Silviculture: Science of forestry production concerned with systematic creation and tending of forests so as to ensure that society's material and intangible needs can be permanently satisfied

Site: Complex of location-related - i.e. natural, economic and social - factors influencing forestry operations.

Stand: Group of trees which exhibit similar features, occupy an unbroken minimum area and all require similar silvicultural treatment.

Welfare function: Also referred to as the indirect effects or non-wood beneficial effects of a forestry operation, i.e. "production" of goods with economic relevance such as water, soil conservation and recreation.

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