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Physical Geography of Northern Eurasia

Biodiversity and Productivity of Ecosystems

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Biodiversity: Definition and Functions

Biodiversity (an abbreviation for biological diversity) is both a scientific and emotive term which is becoming increasingly popular in various areas of fundamental and applied science pertaining to ecology and the environment. Until recently, biodiversity was understood as the diversity of genotypes and species (i.e., as taxonomic richness of biological systems at a level higher than organism) (Wilson, 1988; Chernov, 1991; Zlotin and Yasny, 1992). Now, biodiversity is defined more broadly as the variety of genes, species, and ecosystems that characterizes the Earth's biosphere (UNCED, 1992). By emphasizing the spatiotemporal hierarchy (i.e., from genes to biosphere), this definition reflects both the richness of life on Earth and ecological functions of living matter at all levels of its development through time and space (Wilson, 1988; Zlotin and Yasny, 1992). Biodiversity is of crucial importance to planetary health, local habitats, and single organisms. Indeed, as early as in the middle of the 19th century, Charles Darwin (1859) suggested that more biologically diverse ecosystems are more productive (i.e., they assimilate more carbon dioxide than less biologically diverse ecosystems), if other environmental variables are equal. Since then there has been a debate about this issue and now evidence is emerging that Darwin was correct in his assumption (Mannion, 1996).

Biotic cover (or biosphere) comprises three major groups of organisms — microorganisms (bacteria and fungi), plants, and animals. Biotic cover is a thin film with a global thickness of just 2 cm (Kobak, 1988). The activity of this thin layer, however, results in biological production (global cycling of carbon, nitrogen, and other important nutrients) and maintenance of the equilibrium between production and destruction of organic matter. Biosphere and other components of the natural environment, such as atmosphere, hydrosphere, and pedosphere (soil cover) and components of lithosphere, are intimately linked through global biogeochemical cycles. Thus, the composition of the atmosphere, which is the key to the Earth functioning as an environmental system, depends on the biosphere. These ideas were pioneered by the Russian scientist Vladimir Vernadsky at the beginning of the 20th century (Vernadsky, 1926, 1945, 1980; Kadatsky, 1986). Because of the intimate links between vegetation and climate, the biosphere together with the oceans is implicated in global environmental change. Biodiversity is particularly important in carbon cycling. Destruction diminishes the capacity of vegetation communities to fix carbon and thus the capacity of the biosphere to counteract global warming.

The biosphere and biodiversity are influenced by factors working at present and over large time scales. There are three groups of factors: (1) abiotic factors, mainly climatic, and edaphic (soil and geology); (2) biotic relationships, such as trophic linkages and competition; and (3) anthropogenic (human-induced) factors.

The contemporary geography of biodiversity is determined by the combined impact of all these factors evolving in time. Contemporary environmental science does not consider life as merely passive, evolving as environmental change occurs. On the contrary, the anthropogenic factor is becoming increasingly important. Vernadsky (1926, 1945, 1980) characterized the relationship between humans and biosphere as the 'noosphere' (from the Greek word nods, mind), emphasizing by the introduction of this concept the reciprocal dependence and control of humans and biosphere. Vernadsky had a firm faith in humanity and technology as a force producing change for the benefit of both people and the biosphere. In retrospect, this approach appears Utopian. However, the idea of mutualism remains central to the sustainable use of biodiversity. Studying biodiversity, in the terms of spatial and temporal organization of biotic cover, variety of functional links within environmental systems, and the role of the biosphere in the maintenance of the global ecological balance, remains a key issue in contemporary science (Steffen and Shvidenko, 1996).

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