The conservation of biodiversity requires that we quantify it. But this is no easy task. The term “biodiversity” is a multidimensional concept and cannot be reduced to a single number. Not surprisingly, few published definitions can be used to derive measures that capture its meaning. The challenge that managers face is to choose surrogates for biodiversity – things that can be measured and that represent its multidimensional meanings.1
There is no single definition of biodiversity. In part, this is because the meaning of the term varies between the public, scientists, and policy-makers.
The origin of the term in 19862 coincided with widespread public recognition that human activities were resulting in unprecedented rates of species extinction. The public equated species extinction with loss of biodiversity and biodiversity became synonymous with species richness – the number of species in an area. Species remain the most recognizable component of biodiversity in the realm of popular culture as is evident in the Oxford dictionary’s definition – the variety of plant and animal life in the world or in a particular area.3
In the realm of science and policy-making, biodiversity has been variously defined with over 100 published definitions. There is broad consensus that the meaning of biodiversity encompasses more than the species-focused concept held by the general public. Most definitions of biodiversity include richness and variability in three hierarchical levels of life: genes, species, and ecosystems.4 Ecological processes (or functions) also are important components in these definitions. Ecological processes are interactions of living entities with themselves and with the non-living environment, such as nutrient cycling, gene flow, and predation. Processes are a prominent part of the official definition for the province of British Columbia: Biodiversity is life in all its forms and the habitat and natural processes that support it.5
All these views describe biodiversity as a ‘thing’ with measurable, component parts. While components of biodiversity can and must be measured, the term ‘biodiversity’ is virtually impossible to define quantitatively. Biodiversity is best defined as a concept, not a ‘thing’ – most simply as…differences between living entities and an attribute of life.6
Species are a credible surrogate for the term biodiversity. The use of species richness and its associated values as an operational surrogate for biological diversity connects with public concerns over the loss of species, degradation of ecosystems, and the loss of future benefits derived from biodiversity.6 Such a surrogate is scientifically credible, and can be measured and monitored to guide management decisions. However, other surrogates for biodiversity should also be used since species do not have to go extinct in order for biodiversity to be lost. For example, the loss of old forests represents a significant loss of British Columbia’s biodiversity.
1Purvis, A. and A. Hector. 2002. Getting the measure of biodiversity. Nature 405:212:219.
2Wilson, E.O. 1988. The current state of biological diversity. In E.O. Wilson and F.M. Peter (eds). Biodiversity (pp.3-18). National Academy Press, Washington, DC.
3The New Oxford Dictionary of English. 1998. Oxford University Press, Oxford.
4Bunnell, F.L. and A. Chan-McLeod. 1998. Forestry and biological diversity: Elements of the problem. In F.L. Bunnell and J.F. Johnson (eds). The Living Dance: Policy and practices for biodiversity in managed forests (pp.3-18). University of British Columbia Press, Vancouver, BC.
5BC Ministry of Environment. http://www.env.gov.bc.ca/wld/
6Bunnell, F.L. 1998. Overcoming paralysis by complexity when establishing operational goals for biodiversity. Journal of Sustainable Forestry 7:145-164.