3.2 Key terms and concepts 19
3.2.1 Biodiversity 19
The term ‘biodiversity’ became a buzzword in conservation circles towards the end of the 1980s (Agrawal and Redford, 2006; Blackmore and Reddish, 1996; Cardinale et al, 2012;
Hill et al, 2013; Laurance et al, 2014). Although the term biodiversity is rather new, the origins of the concept go far back in time (Heywood, 1995). A contraction of the term
‘biological diversity’, biodiversity is a concept that embraces the whole array of life forms and their components from genes, through species to habitats and ecosystems (Blackmore and Reddish, 1996; Hambler, 2004; Sandava et al, 2011). It is the totality of genes, species and ecosystems inhabiting a region, and ultimately encompasses the number, variety and variability of life on earth (Agrawal and Redford, 2006; Barbault, 2011; Gaston, 1996;
Heywood, 1995; Mader, 2007; Rands et al, 2010). The term biodiversity has progressed to becoming a powerful symbol for the full richness of life on earth and is now a major driving force behind efforts to reform land management and development practices worldwide and to establish a more harmonious relationship between people and nature (Noss and Cooperrider, 1994; Russell et al, 2011).
The Convention on Biological Diversity (CBD), born out of the 1992 Earth Summit, provides a fuller definition of biodiversity by stating that it is “the variability among living organisms from all sources, including among others, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems” (Hambler, 2004: 11). This all-embracing definition includes the variety of living organisms, the genetic differences among them, the communities and ecosystems in which they occur, and the ecological processes that keep
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them functioning (Barbault, 2011; Gaston, 1996; Hambler, 2004; Noss and Cooperrider, 1994; Pruitt and Underwood, 2006; Sandava et al, 2011).
One of the greatest scientific challenges today involves the measurement of biodiversity (Agrawal and Redford, 2006; Barbault, 2011; Hambler, 2004; Mader, 2007), prompting Guyer and Richards (1996 cited in Brown, 1998: 75) to state that biodiversity is “quantitative without necessarily being quantifiable”. This challenge also appears to be most urgent because, with many species becoming extinct without trace, humanity may never know how many species ever existed on the earth (Hambler, 2004). Some of the levels or measures of biodiversity commonly used include the following:
Genetic diversity: Genes are the sequences of the DNA (deoxyribonucleic acid) molecule and serve as the functional units of heredity (Noss and Cooperrider, 1994; Russell et al, 2011).
Genetic diversity refers to the variation of genes within a species (Blackmore and Reddish, 1996). Species differ from one another genetically while individuals from within a species also vary largely because they have unique combinations of genes (Agrawal and Redford, 2006; Noss and Cooperrider, 1994; Pruitt and Underwood, 2006; Sandava et al, 2011).
Conservation goals at the genetic level include the maintenance of genetic variation within and among populations of species, and ensuring that processes such as genetic differentiation and gene flow continue at normal rates (Noss and Cooperrider, 1994). This is crucial because without genetic variation, populations become less adaptable and their extinction more probable (Noss and Cooperrider, 1994). The aim is therefore to maintain enough individuals of a species so as to ensure that individuals are representative of the genetic variability of the species, thus maximising the gene pool (Blackmore and Reddish, 1996).
Species diversity: Although in some ways species diversity is the best known aspect of biodiversity, it is one that is also not easy to measure (Hambler, 2004; Mader, 2007). This is mainly because biologists have long debated what a ‘species’ actually is (Burgman, 2002;
Hambler, 2004; Mace, 2004; Possingham et al, 2002). Ideally, a species is a group of organisms which can interbreed to produce a fertile offspring, and which are reproductively isolated from other species (Mader, 2007; Sandava et al, 2011). However, this definition is complicated by those species that reproduce asexually, those which can hybridise amongst the ‘species’ and by microorganisms such as bacteria and viruses which can exchange genetic material between very distantly related forms (Hambler, 2004). In addition, the vast majority of species in the world are still unknown and, of an estimated 10 to 100 million species on
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earth, only about 1.5-1.8 million have been named by taxonomists to date (Grena et al, 2014;
Sloan et al, 2014; Stork, 1997; Wilson, 1992). Conservation goals at the species or population level include maintaining viable populations of all native species in natural patterns of abundance and distribution (Noss and Cooperrider, 1994; Sandava et al, 2011).
Ecosystem/ community diversity: A community is an assemblage of species in an area and we can have terrestrial or aquatic communities (Sandava et al, 2011). An ecosystem is a biotic community plus its abiotic environment (Agrawal and Redford, 2006; Mader, 2007).
Ecosystems range in scale from microcosms such as a small pool to the entire biosphere (Noss and Cooperrider, 1994). In most cases, conservation is most efficient when focused directly on the community or ecosystem and should complement species level management (Cumberlidge et al, 2009). The rationale for protecting ecosystems is compelling just because if intact and ecologically functional examples of each type of ecosystem in a region can be maintained, then the species that live in these ecosystems will also survive and persist (Mader, 2007; Noss and Cooperrider, 1994). Practising conservation at the community or ecosystem level thus demands attention to ecological processes (Butchart et al, 2010;
Thuillera et al, 2008).
Landscape and regional diversity: A landscape can be defined as a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form throughout (Forman and Godron, 1986). The term ‘region’ or ‘bioregion’ or ‘ecoregion’ refers to large landscapes that can be distinguished from other regions on the basis of climate, physiography, soils, species composition patterns (biogeography), and other variables (Noss and Cooperrider, 1994). Landscape or regional diversity is pattern diversity (the pattern of habitats and species assemblages over large areas) and is thus a higher level of expression of biodiversity (Noss and Cooperrider, 1994). The primary conservation goal at the landscape or regional level is to maintain complete, unfragmented environmental gradients (Butchart et al, 2010; Cumberlidge et al, 2009).
Cultural or social diversity: During the Keystone Dialogue on Biological Diversity some participants insisted that human cultural or social diversity be included in the definition of biodiversity and in any strategy for its conservation (Noss and Cooperrider, 1994; Keystone Centre, 1991). The Global Biodiversity Strategy also clearly states that human cultural diversity should be considered as part of biodiversity (World Resources Institute - WRI/
IUCN/ United Nations Environment Programme - UNEP, 1992). Cultural diversity is
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manifested by diversity in language, religious beliefs, land-management practices, art, music, social structure, crop selection, diet, and any other attributes of human society (Noss and Cooperrider, 1994).
At face value, the inclusion of cultural diversity in a definition of biodiversity is important because humans are fundamentally as much part of nature as any other species and share kinship and ecological interactions with all life (Hambler, 2004; Noss and Cooperrider, 1994). On closer examination, it is, however, not helpful to make the definition of biodiversity so inclusive, simply because culture changes and also because the protection of culture and the protection of non-human species may sometimes be in conflict (Hambler, 2004). Noss and Cooperrider (1994) further note that including human diversity within the definition of biodiversity would trivialise the concept of biodiversity and make it unworkable.
Such an all-inclusive definition would allow any city in the world to be considered on equal footing with, for example, the Great Barrier Reef of Australia thereby making impossible any coherent discussion of biodiversity conservation (Noss and Cooperrider, 1994). What would probably be workable would be to conserve all cultural approaches that are compatible with the conservation of biodiversity (Cumberlidge et al, 2009; Hambler, 2004; Noss and Cooperrider, 1994). For the above cited reasons, and probably many others, this study does not include cultural diversity within the definition of biodiversity.