Biodiversity

“Biodiversity” is often defined as the variety of all forms of life, from genes to species, through to the broad scale of ecosystems (for a list of variants on this simple definition see Gaston 1996). "Biodiversity" was coined as a contraction of "biological diversity" in 1985, but the new term arguably has taken on a meaning and import all its own. A symposium in 1986, and the follow-up book BioDiversity (Wilson 1988), edited by biologist E. O. Wilson, heralded the popularity of this concept. Ten years later, Takacs (1996, p.39) described its ascent this way: "in 1988, biodiversity did not appear as a keyword in Biological Abstracts, and biological diversity appeared once. In 1993, biodiversity appeared seventy-two times, and biological diversity nineteen times". Ten years further on, it would be hard to count how many times "biodiversity" is used every day by scientists, policy-makers, and others. While the history of this term is relatively short (compare it to other terms covered in this encyclopedia), it already has raised important, distinctive, philosophical issues. Some of these are entangled in the very definition of "biodiversity", an issue treated in the first sections below. A challenge is the reconciliation of process-based and elements-based perspectives on biodiversity. Overall, the major issue for biodiversity is how its conservation may be integrated with other needs of society.

1. Concepts of Biodiversity
The sequel to that first biodiversity book, naturally titled Biodiversity II (Reaka-Kudla et al. 1997), documents the rapid rise of the term "biodiversity" in importance and influence. But it also traces the study of aspects of biodiversity back as far as Aristotle. To some extent, biodiversity merely offers a new, emotive, term for some older ideas and programs. In fact, "biodiversity" is now used sometimes to mean "life" or "wilderness" or other conservation values. "Biodiversity" also has served on occasion as a catch-all for "conservation" itself.
The scientific literature illustrates how most any conservation activity might use the label "biodiversity". On the one hand, workers taking advantage of the acknowledged importance of the term have expanded its meaning to capture concerns at a fine scale, such as that focussing on a favourite single species. This focus might be referred to more accurately as one of "biospecifics". At the coarser scale, one important interpretation, discussed below, advocates a primary linkage of biodiversity to the maintenance of ecosystem processes - what might be called the "bio-processes" approach.

The nub of the problem of defining biodiversity is that it is hard to exclude anything from a concept that is taken so easily to mean "everything". Callicott et al. (1999) examined "biodiversity" as one of the current normative concepts in conservation. They concluded that it remains ill-defined, and that distinctions can be made between "functional" and "compositional" perspectives in approaching biodiversity. "Functional" refers to a primarily concern with ecosystem and evolutionary processes, while "compositional" sees organisms as aggregated into populations, species, higher taxa, communities, and other categories. Callicott et al. call for a better integration of these different perspectives, an issue discussed below [Integrating Process and Elements Perspectives].

Norton (1994) has argued that there will never be a single "objective scientific definition" of biodiversity, in the sense of a prescription for how to measure it. In fact, Norton claims that any increase in our understanding of biodiversity will make it less likely that there will be a single objective measure. This biodiversity pluralism is based on an argument that inevitably there are many different "theory bound" versions of biodiversity and many different ways to value it. This perspective is in accord with recognition of functional-compositional perspectives on biodiversity. For example, Norton (1994; 2001) points to recent emphasis on structure and process regarding ecological "health" or "integrity" that is seen as going beyond a conventional elements-oriented perspective for biodiversity. One cannot aggregate all these different versions of biodiversity. Instead, we are to "describe in ways appropriate given certain purposes" and the choice among these different biodiversity "models" will depend on what values are important to the decision-maker.
2. From Species Values to Biodiversity Values
2.1 Species Values and Triage
In developing ideas about the overall value of biodiversity it has been natural to draw on existing arguments about values of individual species (for review, see World Conservation Union 1980; Norton 1988). Commodity value and other direct use values have intuitive appeal because they reflect known values. But a key problem is that species need to be preserved for reasons other than any known value as resources for human use (Sober 1986). Callicott (1986) discusses philosophical arguments regarding non-utilitarian value and concludes that there is no easy argument to be made except a moral one. Species have some "intrinsic value" - reflecting the idea that a species has a value "in and for itself" (Callicott 1986, p.140) - and there is an ethical obligation to protect biodiversity.


A philosophical issue is whether such species values depend on a human-centered perspective. The "environmental ethics" entry in this encyclopedia [Environmental Ethics] notes that assessments of issues concerned with biodiversity allow for "commitment either to a purely anthropocentric or purely non-anthropocentric ethic". Regan (1986) argues that we need "duties that are independent of out changeable needs and preferences." Callicott (1986) sees the intrinsic value of species as not independent of human values, because such values can be linked to Hume's theory of moral values. Norton (1986) sees all species as collectively embraced by an environmental ethic that is anthropocentric.

Randall (1988, p. 218) has argued that preference is the basis for value and that it is possible to treat all species values as preferences of humans. Preferences-based approaches to valuation can provide economic (dollar) estimates of value. This valuation process may include methods for assessing and quantifying option values. A claimed advantage of such approaches is that the only good way to protect species is to place an economic value on them. Randall argues that such quantification is advantageous because the species preservation option will fare well when the full range of values is included in conservation priority setting.

The context for many of these arguments has been a consideration of various criteria for placing priorities among species for conservation efforts. These considerations have led to debates about the role of "triage" based on species prioritization. Triage recalls the medical context in which priorities are set for investments in saving patients. Applied to conservation, individual species are differentially valued and assessed relative to differential opportunity costs. The best conservation package is to be found through a process of calculating costs and benefits of protection of individual species.

This perspective is characterized as "post-positivist" because it recognizes biodiversity as inevitably value-laden - there is no one, correct, measure of biodiversity to be discovered but many, each having different values. Roebuck and Phifer (1999) lament what they perceive as current "positivism" in biodiversity conservation, described by them as based variously on processes of verificationism and falsificationism in seeking facts. They argue that biodiversity conservation is rooted primarily in ethics and we must not continue to back away from values and advocacy.

Biodiversity may be a catch-all for various aspects of conservation, but the fresh perspectives arising from recognition of "biodiversity" suggest possible unifying concepts. E. O. Wilson (1988) sees "biodiversity" as corresponding to a dramatic transformation for biologists from a "bits and pieces" approach to a much more holistic approach. Wilson describes this change in perspective as a realization that biological diversity is disappearing and, unlike other threatened things, is irreversible. Wrapped up in the term therefore is the idea of a "biodiversity crisis". Ehrenfeld (1988) similarly reinforces this idea of the value of diversity in the aggregate. He argues that diversity previously was never regarded in itself to be in danger, but that biodiversity now is recognised as endangered in its own right. The definition of "biodiversity" sometimes explicitly reflects these links to an extinction crisis. Takacs (1996) reviews cases where the definition of biodiversity is wrapped up in the idea of strategies needed to preserve variation. In accord with this perspective is a shift to a focus on valuing ecosystem processes. This focus arguably will ensure maintenance and ongoing evolution of these systems, and therefore all of biodiversity.

Holistic perspectives on biodiversity have emerged also through another important focus. For Wilson (1988), biodiversity captures the idea of a "frontier of the future", presenting a dazzling prospect of largely unknown variety, with unanticipated uses. Biodiversity is seen by many as a symbol for our lack of knowledge about the components of life's variation, and their importance to mankind (see Takacs 1996). These arguments suggest that core biodiversity values might be based more on what we do not know than what we do know. Biodiversity can be viewed as primarily capturing the two-fold challenge of unknown variety, having unknown value.

Anticipated future uses and values of the unknown are captured in the idea of "option values" (for definitions, see World Conservation Union 1980). Option value corresponds not just to unknown future values of known species, but also to the unknown values of unknown species (or other components of variation). This concept is at the core of biodiversity because it links "variation" and "value". Estimating and quantifying the largely unknown variation that makes up biodiversity is one and the same as quantifying corresponding option values of biodiversity. According to this emphasis, a basic definition of biodiversity might be expanded as: the variety of all forms of life, from the scale of genes through to species and ecosystems …so forming a "calculus" - a means for measurement and comparison - of option values.

Focussing on this core, unifying, aspect of biodiversity does not throw away the other possible "biodiversity" values that might be listed (process-based "resilience" of ecosystems, current commodity values of species, etc.), but facilitates integration of biodiversity's option values with those other values. These possibilities are discussed further in the section Integrating Process and Elements Perspectives.

Given that holistic approaches may integrate functional and compositional aspects, the following sections address these different biodiversity perspectives. The next section addresses the early attempts to address values of biodiversity as a whole that emerged from dissatisfaction with the "bits and pieces" focus on individual species. A later section, Alternatives to Unit-species, presents attempts to address some weaknesses of this initial approach