Part II Biogeography – Biodiversity Hotspots
Louise Sherwin - Girton College
Supervision 2: _ Examine the reasons for the existence and localities of biodiversity hotspots
“I have never experienced such intense delight... such a plenitude of forms, colours, behaviours—such a magnitude of Life! What explains the riot?”
- Darwin (1851)
“The current massive degradation of habitat and extinction of species is taking place on a catastrophically short timescale, and their effects will fundamentally reset the future evolution of the planet's biota.”
- Novacek & Cleland (2001)
Biodiversity may be regarded as ‘the number, variety and variability of living organisms’ (MacDonald, 2003: 406). Whilst global variation in biological diversity has long been a source of fascination, it has recently been the basis for increasing concern (Tilman, 2000). Awareness of the extent and rate of the current biodiversity crisis (or the ‘sixth extinction’, as termed by Leakey & Lewin, 1996) has led to a significant re-assessment of the role of biodiversity in ecosystem functioning and the scope for policy intervention to enable its preservation, exemplified by the international ratification of the Convention on Biodiversity in 1992. The identification and analysis of spatial patterns of biodiversity has been central to conservation goals of maximum preservation at the least cost (Reddy & Davalos, 2003). The hotspots approach is one of many methods for delimiting areas of priority conservation, although it has proven to be one of the most popular. ‘Biodiversity hotspots’ were first introduced by Myers in 1988 and may be defined as:
“areas featuring exceptional concentrations of endemic species and experiencing exceptional loss of habitat” (Myers et al., 2000:853).
By applying parameters to this definition, Myers et al. (2000) identified twenty-five hotpots that predominately represent tropical forests and Mediterranean-type habitat zones (numbering fifteen and five hotpots respectively). In this essay, the reasons for the existence and the localities of biodiversity hotspots will be examined. It should be noted at this stage that biodiversity hotpots do not represent a neutral scientific observation, but are implicitly influenced by human values. The approach encompasses decisions on which aspect of biodiversity is worth conserving (for biodiversity itself is an inconsistently and ill-defined concept according to Gaston, 1996) and the best way to do this from within a framework of economic rationality and efficiency. Perhaps more importantly given the human basis for the rise and power of the concept, the hotspots approach will then be critically considered in terms of how far it adequately meets the needs behind the reasons for its adoption. Following on from this, a number of issues may be identified that undermine the sustainability of the hotpot approach. A critical analysis of the biodiversity hotpot approach raises a number of broader questions for conservation science which lies at the science-action interface, including the need for clear conceptualisation of concepts such as ‘biodiversity’, for modesty when data is incomplete or skewed and a realisation of the impact such suggestions can have on local lives. However, it is first necessary to briefly outline the main characteristics of the hotspots approach.
To identify biodiversity hotpots, Myers et al. (2000) used the dual criteria of over 0.5% plant endemicity (1,500 of the world’s 300,000 plant species) and the loss of 70% or more of its primary vegetation through habitat loss. Twenty-five hotspots were thus categorized, representing up to 44% of vascular plant species and 35% of mammals, birds, reptiles and amphibians in just 1.4% of the Earth’s land surface (ibid., 2000). In terms of primate and carnivore evolutionary history, hotspots maybe even more important, representing almost 70% of evolution for these groups (Sechrest et al., 2002). The premises of the hotpots approach are explicitly outlined by Mittermeier et al. (1998), who state that ‘the biodiversity of… every nation is critical to its survival’, that ‘many areas of high-biodiversity exhibit very high levels of endemism’ and ‘to achieve maximum impacts with limited resources, we must concentrate heavily on those areas highest in diversity and endemism and most severely threatened’. As it was alluded to earlier, the reasons for the existence of biodiversity hotpots are separate and distinct from the reasons for spatial variations of biodiversity. The former represents a conservation approach that utilises the latter as a partial mode to achieve its aims. This is important for the explanation of the reasons for the existence of biodiversity hotpots because ‘conservation only has meaning in the context of human intention’ (Jepson & Canney, 2001: 225). Thus, as a value-based conservation approach, the underlying reasons for the existence of biodiversity hotpots are two fold. Firstly, there has been growing concern of mans’ impact upon the number and extent of species and the conservation of biodiversity is a central tenet of sustainable development theory. Secondly, there is a desire to meet this challenge within the confines of limited resources and demands for economic efficiency. Biodiversity hotpots offer a scientifically based method for policy intervention that meets these dual demands.