CHAPTER ⅩⅤⅢ: HOW MUCH BIODIVERSITY DO WE NEED ?

摘要

Environmental problems are among the major issues the world is facing today. They vary vastly in scale and gravity. Many of these problems are related to economic activities, both past and present. Take, for instance, the over-exploitation of natural resources, which is defined as the intense use of abiotic and biotic resources to such an extent that these become depleted. With abiotic resources, such as the phosphate ores used in the fertilizer industry, depletion occurs by means of dissipation : phosphate is spread out across and within the earth and, subsequently, is no longer available in any practical sense. Phosphate mines are steadily emptied and the related agricultural productivity, which initially had increased significantly, is likely to decline as a result. Reclamation of the by now widely spread-out phosphate is only possible at a very high price in terms of labour and energy. With biotic resources such as wood and fish, which in principle regenerate, problems arise when the level of consumption considerably exceeds the level of regeneration. In extreme cases, biota disappear entirely, resulting in the extinction of the species (Raven 1997).