Biodiversity, water and natural resource management

Measuring biodiversity


The challenge in developing robust quantitative indicators of biodiversity lies in finding those that can be meaningfully applied for policy assessment. Here it is important to note that biodiversity is frequently discussed at different scales. An international debate about global extinction is often divorced from considerations of appropriate micro scales of analysis. Perlman and Adelson (1997) subject the shorthand CBD definition to a basic policy test of whether either a species or an ecosystem is present in a location is fraught with difficulties relating to fundamental definitional problems of what species and ecosystems are. More specifically, where does one species or ecosystem stop and another begin? The absence of any discrete cut-off point for determining boundaries between species or ecosystems is still subject to research and discussion. Even if this problem is overcome, the number of micro-organisms present at any location is likely to be staggering. Moving onto the genetic level, the numbers become even more unmanageable. The Human Genome Project gives some appreciation of the length of endeavour to map the generic code of one species. Repeating the story for thousands more so that there can be some discrimination between them for policy purposes is a truly monumental task. Science has only a limited idea of the genetic dissimilarity between species.

Although there is much interest in the development of indicators or inventories of ecosystem function, species richness is still the common approach to distilling the available information. Species richness is simply a systematic inventory of the number of species contained within an area. This is the commonest method for rapid impact statements about the change in diversity. In terms of approaches to valuation, species richness is also an easy concept to understand. Van Kooten (1998) notes that the measurement of biodiversity involves three aspects: scale, the component aspect and the viewpoint aspect. The scale element is made up of alpha diversity, beta diversity and gamma diversity. Alpha diversity is species richness within a local ecosystem. Beta diversity reflects the change in alpha diversity as one moves from one ecosystem to another across a landscape. Gamma diversity pertains to species richness at a regional or geographical level. This is a more global concept and a measure that is much more dependant on global shocks rather than the local ones (e.g. forest fires) that affect alpha and beta diversity. The component element of measurement concerns the identification of what constitutes a minimum viable population for the survival of a species. This is akin to setting safe minimum standards for species. Finally, the viewpoint issue refers to the existence of many viewpoints, ranging from practical through to moral and aesthetic. Perlamn and Adelson (1997) discuss the assignment of values in more detail. They note that viewpoints are necessarily subjective and value-laden, and that some value criteria have theoretical and legal standing irrespective of either their deliberate use or their ethical foundations.


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