Interaction ofthe Overexploitation Syndrome with other syndromes G 2.4 261 landowners arrive. These players, not really directly related to the Overexploitation Syndrome, can now transform large areas of forest into arable land.These areas are subsequently degraded by the outbreak ofthe Sahel or Dust Bowl Syndrome. In fact, in some cases at this stage the timber companies themselves take on the role of cattle ranchers on the converted forestland, for one thing to obtain long-term land rights and also to invest their profits in stable land assets. This mechanism clearly shows the true potential for damage of selective logging. Since for selective logging of high-grade timbers (such as mahogany) routes of up to 500km first have to be developed (Verissimo et al, 1995), this form of forestry that in many cases is referred to as ‘environmentally friendly’, can cause considerable subsequent damage.‘Small’ interventions of this sort generally lead to the large-scale development of forest areas, which are thus opened up to modern civilization and its various utilization interests. This type of degradation often triggers complete destruction ofthe usable soil layer. This effect ofthe Overexploitation Syndrome as the triggering factor for the Sahel Syndrome andthe Dust Bowl Syndrome is depicted in Fig. G 2.4-1. This process is described in many case studies on tropical deforestation (Heilig, 1994; Walker and Homma, 1996; Mertens and Lambin, 1997; Lambin and Mertens, 1997; Rudel and Roper, 1997; WRI, 1997; Parayil and Tong, 1998; Stone, 1998). This type of causal link also exists between the development of previously inaccessible regions andthe upgrading of infrastructure for the construction of large-scale technical projects (such as dams) andthe mining of mineral reserves. These patterns of environmental degradation were attributed to the Aral Sea Syndrome andthe Katanga Syndrome (WBGU, 1998a), but the Overexploitation Syndrome can set these processes in motion.
G 3 Disposition of forest ecosystems to the Overexploitation Syndrome For any analysis ofthe current dynamic, but above all to identify regions at risk in the future, it is important to ascertain what makes an ecosystem disposed to the Overexploitation Syndrome. In a formal manner, the concept ofthe area of disposition provides a response to the question ofthe conditions under which the interactions ofthe syndrome core are potentially present (QUESTIONS, 1998). Expressed in practical terms, the area of disposition covers those areas ofthe Earth in which there is a particularly high probability that the syndrome will emerge in the future. Forests are seen as being disposed towards the Overexploitation Syndrome when the short-term, large-scale economic use oftheir wood products is both possible and probable. Other products ofthe forest ecosystems can be ignored in this context if their extraction does not bring with it the exploitation ofthe entire ecosystem. So the disposition is linked not just to the existence of forests but also to their potential economic use.This depends on a number of different factors which will be discussed below. G 3.1 Disposition factors The mechanisms characteristic ofthe Overexploitation Syndrome can only take hold if forest areas have a potential economic use.The potential economic use hinges on the density ofthe timber or biomass in a given area and on it being possible to reach those resources at as reasonable a price as possible. The relationship between transport costs, land use and deforestation is well documented (Lambin and Mertens, 1997; Cassel-Gintz, 1997; Stone, 1998) and can be explained in economic terms in the tradition of von Thünen’s theory of land rents (Schätzl, 1988). The main premise is that land use is determined by the distance to the point of sale dependent on transportation costs (including development costs) andthe sales price (Stone, 1998). The density of biomass that can be put to economic use was estimated with the help of expert assessments (Kohlmaier et al, 1997) and a model on global vegetation dynamics (Sitch et al, 1999) and, using a compensatory AND-function, linked to accessible forest resources.A minimum biomass density required for economic viability is assumed. The forest data used were taken from the World Forest Map (WRI, 1998b), that was transformed into 5’ grid cells (around 10 x 10km at the Equator). However not all forest areas qualified as accessible are disposed to the syndrome to an equal degree. In many regions ofthe world the governments, from time to time under international agreements, have established protected forest areas with differing degrees of limitation on use. Areas with a protected status of Classes I-V according to the IUCN classification (Section E 3.3.2) are designated for political and legal reasons as non-usable. Protection against illegal logging through designation of protected areas (eg biosphere reserves under the MAB programme, Section E 3.9) may often be seen as inadequate and is dependent on local factors that vary with time. Thus the estimation of local legal certainty in these protected areas in the context of short-term influencing factors is assessed in the context of measuring intensity (Section G 4) and so is not significant here. The accessibility of forests was simulated by means of a virtual cost calculation.The basic assumption was that forest areas that can be reached at a low cost are exploited before those that will take a large degree of technological and organizational input to develop and use. In order further to define that input, a fuzzy logic-based linkage operation was performed on the following factors: – proximity to roads and railways, – proximity to flat coastal areas, – proximity to urban centres and dense areas of settlement, – gradient in the topography ofthe terrain. Permafrost areas and navigable rivers with no icefree ports were categorized as accessible only with great difficulty. The map that was produced (5’ grid) indicates the potential accessibility of forest areas andthe relative costs required to develop the area