Focus on global forest ecosystems G 1.3 251 between the amount caught andthe recruitment rate the following year. By contrast, in the case of forests the growth is calculable andthe consequences of unsustainable management are immediately evident. Having said that the shorter life cycles ofthe most important fish caught also make it possible for relatively quick regeneration. Therefore, forward-looking strategies of risk minimization with higher uncertainties are particularly important here (WBGU, 2000a). The Overexploitation Syndrome in the form of overfishing is also characterized by the fact that for a limited time there is the possibility of maintaining the capacities following overuse of a sub-region by shifting to another sub-region. The fishing fleets push out into ever-new fishing grounds and catch new species, mostly those that were not interesting until the ‘superior’ species had been overfished. In the case of overfishing, geographic areas can be determined that are potentially prone to the Overexploitation Syndrome. This disposition is determined both by biogeographical factors andthe socio-economic structures described above.With regard to the former, ecosystem factors include oxygen and nutrient content in the waters allowing high plankton production in the layer of water close to the surface. In that way, particularly the coastal and shelf regions as well as marginal seas can become vulnerable. In relation to the far larger habitats ofthe open seas these areas represent a small subsystem, but they account for approx 90 per cent of fish production. As a result of socio-economic factors areas that lie outside the 200 mile Exclusive Economic Zone are more likely to be affected since the direct influence of governments is much smaller. That also applies to the coastal waters of states that are not in a position to monitor their fishing rights effectively. Annihilation and threat to individual species The trade in individual animal and plant species has on a regional level led to considerable intervention in ecosystems, which is the reason why today approx 5,000 animal species and 25,000 plant species are protected by the Convention on the Trade in Endangered Species of Wild Fauna and Flora (Section D 3.4). (International) trade is often a reaction to very specific needs associated with culture, lifestyle or tradition. For instance, in Southeast Asia one can observe a severe loss of valuable animal species such as tiger and rhinoceros for the production of traditional remedies, particularly Chinese remedies. In more recent times the use of medicinal plants for pharmaceuticals commonly used in Europe has also endangered certain species. The desire for luxury goods continues to be a motive for trade in ivory, reptile skins or the furs of rare predators. For other species such as whales, hunting is lucrative simply because ofthe rich diversity of uses for the booty. Common to all cases is the short-term use disregarding necessary regeneration periods so typical ofthe Overexploitation Syndrome, which in many cases has led to the eradication of species, and indeed still does today. G 1.3 Focus on global forest ecosystems Cognizant ofthe diverse manifestations ofthe Overexploitation Syndrome, forest ecosystems will be subject to a syndrome analysis below in the following sections. G 1.3.1 The forests ofthe Earth: Stocks and threats Development of forest stocks Global forest areas have in the course of history become ever more subject to humankind’s influence. When agrarian cultivation was introduced around 10,000 years ago an estimated 6.2 thousand million hectares were covered by forest worldwide (Burschel, 1995; WRI, 1997). The current area covered by forest is given at around 3.45 thousand million hectares, of which half is tropical forest (1.76 thousand million hectares) andthe other half boreal (0.93 thousand million hectares) and temperate forests (0.75 thousand million hectares; FAO, 1997b). This corresponds to a decline from 40 per cent to 27 per cent ofthe ice-free land surface over the last 10,000 years and documents the continuation ofthe process of deforestation. The global distribution ofthe present-day and historical forest resources is given in Fig. G 1.3-1. Current forest area changes Between 1980 and 1995 global forest cover declined by 180 million hectares (Fig. G 1.3-2). Above all in developing countries around 200 million hectares of forest was destroyed, primarily for agricultural use – a development which many industrialized countries went through in the early stages oftheir development (Brüggemeier, 1998). In that same period, however, a growth ofthe surface area of forest cover as a result of afforestation and set-aside agricultural land was recorded (FAO, 1997b).
252 G Biosphere-anthroposphere linkages: The Overexploitation Syndrome Current primary forests Primary forest losses during the last 3,000 years Figure G 1.3-1 Distribution of primary forest and forest types. Source: Cassel-Gintz et al, 1999 Change in forest area (1990–1995) [% year -1 ] -10% – -6% -6% – -3% -3% – 0% >0% No data Figure G 1.3-2 Annual rate of forest cover change between 1990 and 1995. Source: Cassel-Gintz et al, 1999