## 1. Pre-History of "Biodiversity": Variety and Its Values



The term "biodiversity" was coined around 1985, but the
conceptual, and political, foundations for the new term were developed
over at least the previous decade. The link between biotic diversity
and human well-being is clear in the "pre-history" of the
term "biodiversity" (roughly, the history of the term
before it was invented). Much of the early work recognising a species
extinction crisis naturally focussed on the values of individual
species to humanity, in addition to their intrinsic value (for
reviews, see Farnham 2007; Mazur & Lee 1993). Discussions by Myers
(1976) and others broadened this focus to include a concern about the
consequent overall loss of variety, and why such a loss of variety
itself matters to humanity. Haskins (1974: 646) summarised an
important discussion meeting where participants called for



> 
> 
> an Ethic of Biotic Diversity in which such diversity is viewed as a
> value in itself and is tied in with the survival and fitness of the
> human race.
> 
> 
> 



Haskins (1974: 646) argued, "Plants and animals that may now be
regarded as dispensable may one day emerge as valuable
resources" and that extinction "threatens to narrow down
future choices for mankind" (see also Anonymous 1974).
Similarly, Roush (1977: 9) argued that "diversity increases the
possibility of future benefits" (for review, see Farnham
2007).



Myers (1976) arguments for a greater focus on the overall loss of
variety appeared in his paper, "An Expanded Approach to the
Problem of Disappearing Species". He argued that



> 
> 
> ...the spectrum of species can be reckoned a repository of some
> of society's most valuable raw materials. Moreover, loss of
> species will affect generations into the indefinite future, whose
> options to utilize species in ways yet undetermined should be kept
> open. (see also Josephson 1982)
> 
> 
> 



Myers and Ayensu (1983) similarly argued that the possible discovery
of benefits for humans is a primary justification for conservation of
biological diversity (see also Myers' 1979 book, *The Sinking
Ark*).



This pre-history considered variety at more than the species level.
Farnham (2017) provides a useful historical perspective, describing
how the standard three levels of variation later recognised by the
Convention on Biological Diversity (CBD)--genes, species, and
ecosystems--became established early as parts of our broader
concern about the loss of living variation. He describes this as a
convergence of separate concerns about species loss, loss of genetic
variety, and the disappearance of ecosystem types. Other support for
this convergence is found in early work referring to the variety of
biomes or ecosystems as capturing variety at the species level. For
example, Ehrenfeld (1970) referred to the potential but unknown uses
of species and suggested conserving the full variety of ecosystems to
capture these future options (arguing that every ecosystem is likely
to have some useful species). Back in 1972, the botanist, H. H. Iltis,
argued that we must "preserve sufficient diversity of species
and of ecosystems" because "we will never reach a point
where we shall know which organisms are going to be of value to man
and which are not" (Iltis 1972: 204). Ehrenfeld referred to the
need globally to conserve a representative set of the different
ecosystems (see also Roush 1977). Echoing these concerns, Wilson
(1984) later lamented the lack of representativeness of the variety of
ecosystems in the current protected areas system.



Thus, while important early discussion (Lovejoy 1980) linked
"biological diversity" to species richness, the full
spectrum of the early work reveals precedents for considering multiple
levels--all with conceptual links to the species extinction
crisis.


### 1.1 Multiple benefits of biotic diversity: insurance and investment



Those bits of pre-history clearly articulate the idea that variety
itself is important because it maintains future options for humanity.
However, this early work did not establish any consistent terminology
to describe this. Later work (see below) uses terms like biodiversity
"option value" (a term used in other ways in economics)
and "maintenance of options" (a term that includes other
contributions from nature, not just those from
variety/biodiversity).



Back in 1980, the IUCN (International Union for Conservation of
Nature) reflected on this earlier work, and offered some distinctions
that are still useful in philosophical discussions about biodiversity
definitions and values. IUCN's (1980: section 3) arguments for
the conservation of diversity (referring to "the range of
genetic material found in the world's organisms") echoed
earlier statements about variety and future options:



> 
> 
> we may learn that many species that seem dispensable are capable of
> providing important products, such as pharmaceuticals....
> 
> 
> 



Importantly, IUCN also echoed other early work, in adding a critical
second part to that sentence: "...or are vital parts of
life-support systems on which we depend" (IUCN 1980: section 3).
IUCN provided terms for these two ways in which variety itself
benefits humanity:



> 
> 
> preservation of genetic diversity (their stand-in for the
> not-yet-defined "biodiversity") is both a matter of
> insurance and investment to keep open future options. (IUCN 1980:
> section 3)
> 
> 
> 



It is informative to trace this insurance and investment duality in
the pre-history of "biodiversity". Roush (1977) listed
four reasons for preserving "natural diversity". In
addition to the relational values concerning "human
delight" and ethics, his reasons included not only the idea that
"diversity increases the possibility of future benefits"
but also that diversity supports stability of the "life support
system".



Holdren and Ehrlich (1974) argued that loss of a species or loss of
genetic diversity can mean loss of potential uses (medicines, foods
etc.), but also referred to the maintenance of the "public
service" functions of natural ecosystems. Ehrenfeld (1970)
similarly distinguished between the within ecosystem
functioning/stability argument and the potential uses or option value
argument. Ehrlich and Ehrlich (1981), in their book
*Extinction* discussed the insurance value of the Earth's
"biological diversity" through the analogy of popping
rivets off an airplane wing--we strive to keep all the rivets,
because we do not know how many could be lost before the wing no
longer functions.



This pre-history of "biodiversity" thus considered
multiple values for humanity from living variation itself, building on
the even-longer history of basic awareness that there lots of kinds of
things (e.g., species; for review, see Oksanen 2004). This
argumentation also added to discussions that had considered
attribution of "intrinsic value" to variety of life (see
the supplement on
 biodiversity preservation
 in the entry on environmental ethics, for discussion of intrinsic
value.


## 2. Later Work on Variety, Its Value, and the Question of Normativity



The new term "biodiversity", post-1985, marked fresh
perspectives about what variety or "diversity" might mean,
and what the benefits and values of biodiversity might be. There also
was a continuation and further development of the core perspectives on
value established during the pre-history. Wilson (1985) made the case
for a "biological diversity crisis" by arguing that this
means the loss of potential uses, yet to be discovered. Wilson also
echoed Myers and Ayensu (1983) and others arguing for the importance
of systematics and the need for discovery of species to address
knowledge gaps. Later, Wilson (1988) brought these arguments together,
arguing that the new term "biodiversity" reflects our lack
of knowledge about the components of life's variation and their
importance to humankind.



The pre-history perspectives, in the writings of Myers and others,
influenced the Brundtland Report, a landmark United Nations report on
sustainable development (WCED 1987). This report contains the
much-quoted definition:



> 
> 
> Sustainable development is development that meets the needs of the
> present without compromising the ability of future generations to meet
> their own needs.
> 
> 
> 



This is followed by a key requirement:



> 
> 
> The loss of plant and animal species can greatly limit the options of
> future generations; so sustainable development requires the
> conservation of plant and animal species.
> 
> 
> 



The report's call for governments to form a "species
convention" helped catalyse the creation of the Convention on
Biological Diversity (CBD; see below).



These perspectives foreshadow later discussion themes, including:
further exploration of biodiversity option value (including the
question of normativity); analysis of what we mean by
"variety" and how we measure it; and further exploration
of the "insurance" aspect of biodiversity value (setting
the stage for a multitude of ecological interpretations of
"biodiversity").


### 2.1 Further exploration of biodiversity option value



Post 1985, the new term "biodiversity" was central to
perspectives on the value of living variation. McNeely (1988) and Reid
and Miller (1989) highlighted option values of biodiversity (see also
Norton 1986). Later, a landmark global report, the Millennium
Ecosystem Assessment (2005: 32), summarised twenty-plus years of
"biodiversity" conservation, concluding that



> 
> 
> the value individuals place on keeping biodiversity for future
> generations--the option value--can be significant.
> 
> 
> 



Another decade later, Gascon et al. (2015) reviewed the many, often
surprising, benefits of species to argue for the importance of
biodiversity option value. Gascon et al. also echoed the earlier
proposals that "phylogenetic diversity", a measure of
biodiversity based on the tree of life, is a natural way to measure
this option value (see section below).



Around that time, the Papal Encyclical Letter "On Care for Our
Common Home" (Francis 2015) addressed the loss of biodiversity,
arguing for the importance of not only intrinsic values of species but
also the option values of biodiversity:



> 
> 
> The loss of forests and woodlands entails the loss of species which
> may constitute extremely important resources in the future, not only
> for food but also for curing disease and other uses. Different species
> contain genes which could be key resources in years ahead for meeting
> human needs and regulating environmental problems. (2015: 32)
> 
> 
> 



These arguments referring to surprising benefits from individual
species sometimes have not make it clear whether such values are being
considered for individual species (only), or for variety itself. The
IPBES Conceptual Framework (Diaz et al. 2015: 14) refers to



> 
> 
> the "option values of biodiversity", that is, the value of
> maintaining living variation in order to provide possible future uses
> and benefits.
> 
> 
> 



However, later IPBES discussions of "nature's
contributions to people" use related terms in a more general
way. Here, Diaz et al. (2018: Table S1) describe
"maintenance of options" as the "Capacity of
ecosystems, habitats, species or genotypes to keep options open in
order to support a good quality of life". This broad statement
seems to cover both individual elements and variety itself.



Bartkowski (2019) in his "Valuation of Biodiversity"
review, notes that perspectives about economic values of
"biodiversity" typically have focussed on individual
elements, with the less-attention to the values of variety, including
both option and insurance values. This concern echoes earlier debates
that have examined whether option value applies to
biodiversity-as-variety, and not just to specific elements.
Consideration of the potential future benefits from individual species
can be interpreted as implying a value for variety (Maclaurin &
Sterelny 2008: 154):



> 
> 
> The crucial point about option value is that it makes diversity
> valuable. As we do not know in advance which species will prove to be
> important, we should try to conserve as rich and representative a
> sample as possible.
> 
> 
> 



Maier (2012), in his book, *What's So Good About
Biodiversity?*, criticised Maclaurin and Sterelny's
arguments for biodiversity's option value. However, this
critique may reflect simply a focus on individual elements rather than
variety itself. Maier interpreted "option value" as
applying, in accord with economics usage, to a given element,
resource, or ecosystem service. Any quantification of value, Maier
argued, would require estimates of reliability of stock, risk
aversion, and willingness to pay--all missing in Maclaurin and
Sterelny's arguments. These views are partly reconciled by
recognising that reference to "option value of
biodiversity" is a current value of variety itself, and does not
have to be interpreted to mean that the actual value of the future
benefits is determined. This difference in perspectives also has
played a role in debates about whether biodiversity option value has
normative standing.


### 2.2 Variety, value and normativity



Biodiversity as variety provides option/investment and insurance
benefits to humanity, but this leaves open the question as to the
nature of the value of such benefits. Haskins (1974) had called for
"an Ethic of Biotic Diversity", in which variety's
benefit has ethical import because we care about the well-being of
future generations. Similarly, when IUCN (1980: Section 3) reviewed
the arguments for the conservation of biotic diversity, they linked
this to moral principles:



> 
> 
> The issue of moral principle relates particularly to species
> extinction, and may be stated as follows. Human beings have become a
> major evolutionary force. While lacking the knowledge to control the
> biosphere, we have the power to change it radically. We are morally
> obliged-to our descendants and to other creatures-to act
> prudently... We cannot predict what species may become useful to
> us. Indeed we may learn that many species that seem dispensable are
> capable of providing important products, such as pharmaceuticals, or
> are vital parts of life-support systems on which we depend. For
> reasons of ethics and self-interest, therefore, we should not
> knowingly cause the extinction of a species.
> 
> 
> 



This early discussion, linking biodiversity's option value to
ethical/moral obligations to future generations, anticipated the
rationale for the Convention on Biological Diversity (CBD). Schroeder
and Pisupati (2010: 9) in "Ethics, Justice, and the Convention
on Biological Diversity", note that the CBD statements on
conservation of biodiversity include consideration of
intergenerational justice:



> 
> 
> The first CBD objective, the conservation of biodiversity, is an
> urgent act of attaining intergenerational justice; an act that
> requires sustained, engaged international collaboration. To deplete
> the planet of essential resources and leave to future generations a
> world which severely limits their options, is unjust.
> 
> 
> 



In this context, biodiversity is valued (now) because we care about
the welfare of future generations; thus, we see a current benefit, and
a link to justice, in biodiversity's maintenance of options for
future generations. This is seen as a kind of relational value,
relating the present generation to future generations (Faith 2017:
76):



> 
> 
> the best argument for what we call the option value of biodiversity is
> that we see many currently beneficial units, and maintaining a large
> number of units (biodiversity) for the future will help maintain a
> steady flow of such beneficial units... Biodiversity option value
> therefore links "variation" and "value":
> providing a fundamental relational value of biodiversity reflecting
> our degree of concern about benefits for future generations
> 
> 
> 



Intergenerational justice or equity is linked to both
investment/options and insurance (Bartkowski 2017: 53):



> 
> 
> ...the two perspectives--insurance and options--are
> inherently interlinked; however, they depend on different types of
> uncertainty (supply vs. demand), which makes the differentiation
> sensible. The view of biodiversity as carrier of option value stems
> from the recognition that a biodiverse ecosystem, which contains many
> different species and genomes, can best accommodate unanticipated
> future desires (preferences). As in the case of insurance value, this
> can be coupled with considerations of intergenerational equity. In
> fact, in the case of option value, this notion is arguably more
> central: high levels of biodiversity now mean many different options
> for our descendants.
> 
> 
> 



An important consideration in recognising an ethical/moral/justice
imperative to conserve biodiversity is the recognition that
biodiversity, as variety, has a current benefit/value because of that
relational link between generations. However, other framings omit this
idea of a current benefit from variety itself. For example, Binder and
Polasky (2013), in the *Encyclopedia of Biodiversity*, list
ways that biodiversity links to human well-being.



> 
> 
> Biodiversity contributes to human well-being directly through
> provision of foods, fuels, and fibers, and indirectly through its role
> in enhancing ecosystem functions that lead to the provision of
> ecosystem services.
> 
> 
> 



This might seem to capture biodiversity option value in referring to
foods and other goods, but in fact leaves out the idea that society
sees biodiversity and the prospect for discoveries for future
generations as a current contribution to well-being. The well-being is
not just that realised when the new product is discovered.



Such a restricted interpretation can mean that the maintenance of
options provided by biodiversity fails to enter into assessments. For
example, Brauman et al. (2020) set out to assess the current global
status of nature's contributions to people, but explicitly chose
not to assess maintenance of options--arguing that this is a
contribution to well-being only through its support of the well-being
obtained from other contributions of nature. In contrast, the IPBES
global assessment (IPBES 2019) did assess global status of maintenance
of options, noting that, even when considering other specific nature
contributions, such as medicinal resources, biodiversity's
maintenance of options is a current benefit in promising possible
future medicinal benefits (see also "Phylogenetic diversity and
IPBES" in Other Internet Resources).



Absence of recognition of the current benefit of biodiversity's
maintenance of options has other implications. Maier's (2018)
arguments that biodiversity option value has no normative standing are
based on an assessment of variety as a future, not current, benefit.
An alternative argument, supporting normative standing, focuses on
biodiversity-as-variety as a current benefit, because this variety is
recognised as maintaining options for future generations. This current
value links to normativity--we ought to act to conserve
biodiversity and its maintenance of options because it is the right
thing to do, given that we care about, and have some relational moral
obligation to future generations (Faith 2018a). These discussions
highlight the idea that both "current benefit" and
"future benefit" are relevant to biodiversity option
value. Biodiversity is a benefit currently because it offers
unanticipated future benefits, and given the relational sense of
obligation to future generations is a basis for normativity.



Another entry in the *Encyclopedia of Biodiversity*, Chan and
Satterfield's (2013) "Justice, Equity and
Biodiversity", supports this idea, in linking biodiversity
conservation to justice for future generations. However,
"biodiversity" is left undefined, and seen as something
that exists within ecosystems that maintains ecosystems services for
future generations. The focus on ecosystem services (where
"biodiversity" often has ecological interpretations; see
section below) means that the value of variety itself is left unstated
by the authors.



Some perspectives give less emphasis to the idea of variety and its
benefit/value, and in these, the arguments for a normative status for
"biodiversity" appear to be weaker. For example, Koricheva
and Siipi (2004: 46) see only intrinsic value as a pathway for moral
obligation to (overall) biodiversity:



> 
> 
> If biodiversity is found to be intrinsically valuable, we have strong
> moral reasons to conserve all aspects of biodiversity, regardless of
> their potential utilitarian and instrumental values. If, conversely,
> biodiversity is found to be only instrumentally valuable, then on
> moral grounds we can demand conservation only of those parts which
> (directly or indirectly) enhance (or will in the future enhance) the
> well-being or quality of some other valuable entity or state of
> affairs.
> 
> 
> 



Given this perspective, they conclude that: "conservationists
are burdened with the need to find or create instrumental values for
each biodiversity element". Similarly, in "The Moral Value
of Biodiversity", Oksanen (1997) concludes that "It is not
the thing 'biodiversity' that is of ultimate moral value,
but its various constituents". Thus, this argumentation seems to
be disconnected from the idea that, collectively, all of the
"elements" or "constituents"--the
variety--delivers biodiversity option value and justice for
future generations.



Significantly, the popular instrumental-versus-intrinsic argumentation
has sometimes meant a neglect of biodiversity option
 value.[1]
 Commonly, the instrumental value of biodiversity is characterised as
all about supporting of functions/resilience within ecosystems, not
global option values. Some literature suggests that relational values
importantly move beyond the standard instrumental-versus-intrinsic
framework (e.g., Himes & Muraca 2018). In the context of
biodiversity option value, greater appreciation of relational values
in fact restores a link to biodiversity value that has been obscured
by the popular instrumental-versus-intrinsic argumentation.



The link to variety, as compared to individual elements and/or other
ecosystem/ecological aspects, is an issue in other discussions. Eser
et al. (2014) acknowledge a normative content for biodiversity, and
consider it as arising from the politics at that time ("the
making of the term 'biodiversity' indicates that the
concept is morally impregnated", 2014: 38). They argue that



> 
> 
> the Convention on Biological Diversity, not only addresses issues of
> conservation, but also sustainable use and fair sharing of benefits.
> This triad of objectives reflects the three dimensions of sustainable
> development: ecology, economy and society. (2014: 38)
> 
> 
> 



This equation may imply that the justice/normativity link is to be
interpreted as depending on the "fair sharing of
benefits". This fair sharing of benefits often is played out
locally, while the conservation of biodiversity is more a global CBD
issue. Thus, there does not seem to be a tight fit between Eser et
al.'s historical perspective, tied to the origins of the term
"biodiversity", and the deeper historical perspective of
ethical arguments for the conservation of biotic diversity. Indeed,
Eser et al. do not provide any explicit analysis of the benefits and
value of biodiversity-as-variety. Instead, they see the wide range of
notions of "biodiversity" as quite useful in providing a
"boundary" object that can embrace lots of meanings and
perspectives about value. A similar perspective is found in a proposed
"weak deflationism" for biodiversity (see below), where
what is regarded as "biodiversity" is the outcome of
"normative discussion of what merits conservation".



Eser et al.'s arguments nevertheless are compatible with the
early ideas, going back to Haskins and others, of a normative reason
to protect biodiversity-as-variety for future generations.
Significantly, Eser et al. (2014: 94) argue that:



> 
> 
> consideration of the needs of future generations does not count as
> "nice to have" but is considered a "must".
> Finding the appropriate balance between obligations to current and
> future generations is one of the main challenges of global change
> ethics.
> 
> 
> 



Eser et al. conclude (2014: 95)



> 
> 
> the moral belief that our dealing with the needs of future generations
> is a matter of Justice is so widespread that it can almost count as a
> truism. To substantiate biodiversity strategies with the rights of
> future generations therefore is a promising strategy because it meets
> the intuitions of so many people.
> 
> 
> 


### 2.3 What do we mean by "variety" or "diversity" and how do we measure it?



During the pre-history of "biodiversity", the species
extinction crisis provided motivation to consider the value of living
variation, covering not only species richness but also genetic
variation and the variety of ecosystems. The new term
"biodiversity" introduced fresh considerations,
particularly reflecting ecology and ecosystems perspectives. The CBD
definition of "biodiversity" used two terms,
"variability" and "diversity", that have
invited multiple interpretations:



> 
> 
> ... the variability among living organisms from all sources
> including, inter alia, 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.
> 
> 
> 



The definition of "biodiversity" in the IPBES Glossary
(see the link in
 Other Internet Resources)
 partly follows that of the CBD:



> 
> 
> The variability among living organisms from all sources including
> terrestrial, marine and other aquatic ecosystems and the ecological
> complexes of which they are a part. This includes variation in
> genetic, phenotypic, phylogenetic, and functional attributes, as well
> as changes in abundance and distribution over time and space within
> and among species, biological communities and ecosystems.
> 
> 
> 



The vague open-ended term "diversity", in the CBD
definition, can be interpreted as any of a number of ecological
diversity indices (see below). In contrast, IPBES reflects pre-history
in shifting to the word, "variation". Naturally, this word
has provided its own interpretation challenges, including how to
characterise it consistently across different levels of variation.
Weitzman (1992) presented an influential general framework for
biodiversity as variation, based on the idea of objects, and measures
of difference between objects. Biodiversity (amount of variation) then
depends not only on the number of objects, but also the degree of
differences among them. In the book *Philosophy and
Biodiversity*, the link between "biodiversity" and
investment and insurance value is described as depending on:
"The higher the number and the degree of difference between
biological elements" (Koricheva & Siipi 2004: 39). Weikard
(2002) argued that any operational concept of biodiversity must have
some measure of difference between objects (see also Maclaurin &
Sterelny 2008; Morgan 2009).



This strategy assumes that we can define meaningful differences among
the initial objects, and also sort out the trade-off between having
more objects versus bigger differences. One difficulty is that there
are many ways to define "differences". Morgan (2009)
concluded that, even if one has some agreed natural measure of
differences, we do not know how to trade off more objects for less
differences (or vice versa) to assess biodiversity.



An alternative general framework, proposed by Faith (1994), avoids
weaknesses of the objects-differences strategy. The framework
side-steps the idea of differences and instead uses the inferred
relative number of biodiversity "units" among any given
set of "objects". If "biodiversity" is
variation or variety in the sense of units (such as species) that we
ideally count-up, then what are those units or elements that make-up
biodiversity? The units of interest logically cover more than just the
species level (and even the core idea of "species" may
consider alternative classifications, such as those in folk cultures;
Oksanen 2004). Maclaurin and Sterelny's argument (2008:
154) that option value "links variation and value"
considered option value for units across all levels of
biodiversity.



A common assessment of biodiversity-as-variety evaluates a set of
protected areas and asks "how many different species are
represented by that set of areas?" In the general framework,
this converts to a more general biodiversity question: "how many
different units are represented by that set of objects?" Thus,
"species" corresponds to just one kind of
"unit" of variation (with different species as different
"units"), and areas are just one kind of
"objects". Biodiversity assessment considers a wide range
of these possible objects for decision-making--not just areas,
but also species, populations, and other entities. Biodiversity
therefore can be quantified in general as a count of the number of
different units represented by a given set of objects. Examples of
other objects/units combinations include species/traits (or features)
and species' populations/genetic variants.



A strength of the framework is that it addresses the fact that many of
the "units" are unknown, and so, cannot simply be
counted-up. Many species are still unknown to science; many features
of species are undescribed. We may directly observe some objects (say,
species) and want to quantify the relative number of un-observed units
(say, features) that are represented by those objects. The relative
number of units for any object or set of objects therefore has to be
estimated through the use of an inferential model or a surrogate of
some kind.



A model that successfully reflects the underlying processes that
determine the distribution of units among objects (a
pattern--process model) may tell us enough about the
relationships among the objects to enable inference of relative
numbers of units represented by any set of those objects. This is the
rationale for a general framework for using pattern to quantify
diversity at a level below that of the original objects.



Thus, relationships among different objects ) informs us about what is
of interest: the amount of biodiversity, expressed as the number of
units represented by those objects. This "counting-up" of
the lower-level units means that we can compare different sets of
objects by the count of the number of different units represented, and
look at useful information such as gains and losses as the set
changes.



Suppose, for example, that the units of interest are features of
species (a feature might be some morphological characteristic). These
features in general have unknown future benefits; feature diversity
provides another example of biodiversity option value. If we apply the
rationale that all these features should be treated as units of equal
value, then some species (those that are phylogenetically distinctive;
see below) will make larger contributions to the overall feature
diversity represented by a set of species. Thus, equal value at the
fine scale among features leads to differential values at the coarse
scale among species.



Feature diversity raises measurement challenges. Not only do we not
know, in general, the future value of different features, but also we
cannot even list the features for most species. Phylogenetic pattern
provides one way to estimate and quantify variation at the feature
level. The predicted total feature diversity of a set of species is
referred to as its "phylogenetic diversity" (PD). The
amount of PD, and the estimated relative feature diversity, of a set
of species is calculated as the minimum total length of all the
phylogenetic branches required to connect all the species in that set
on the phylogenetic tree (Faith 1992). This definition follows from an
evolutionary model in which branch lengths reflect evolutionary
changes (new features), and shared ancestry accounts for shared
features among species. Note that a set of three species may have
lower PD (lower feature diversity) than a set of two species (see
figure below).



The phylogenetic diversity measure illustrates how the
pattern--process framework differs from the objects and
differences approach. For PD, the objects are species (or other taxa)
and the units that we would like to count-up are features (or
characters). The use of phylogeny (the "tree of life") to
make inferences about the relative feature diversity of different sets
of species is a way to overcome our lack of knowledge about all the
features of different species. Maclaurin and Sterelny (2008: 20)
incorrectly interpreted PD as an application of the objects and
differences approach, with species as objects and differences given by
"genealogical depth". Instead, a pattern (phylogeny) among
the species is used. This pattern allows inferences about the
biodiversity units of interest--here, features or characters of
species.





![a diagram: link to extended description below.](figa.svg)

(a)




![a diagram: link to extended description below.](figb.svg)

(b)





Figure. A general biodiversity model
linking relationships among objects to measures of biodiversity based
on the indirect counting-up of units. In each case, relationships
among the three objects represented by solid dots provides information
about their representation, as a set, of underlying units. The ovals
highlight the idea that their degree of similarity within the pattern
indicates degree of shared units.


1. for phylogenetic diversity, the objects are species, the units are
evolutionary features and the phylogenetic/feature diversity of the 3
(solid dots) species is indicated by the summed lengths of the blue
branches on the phylogenetic tree. Note that this set of 3 species has
greater phylogenetic diversity / feature diversity than the set of two
hollow-dot species (red branches). [An
 extended description of figure (a)
 is in the supplement.]
2. another kind of pattern for species-as-objects is a Euclidean space
representing key environmental gradients. The inferred biodiversity
may be functional trait diversity. [An
 extended description of figure (b)
 is in the supplement.]




Sarkar's (2014: 3) consideration of "units" other
than species appears compatible with the general pattern-process
framework. However, Sarkar's proposal differs in integrating
other additional calculations into the quantification of biodiversity.
For example, Sarkar proposed that biodiversity must include a number
of aspects beyond richness. At the species-level, Sarkar (2014: 3)
argued that a measure of biodiversity should reflect complementarity,
rarity, endemism and also "equitability" (reflecting
relative abundances). Another aspect to be included was
"disparity" reflecting taxonomic distance between species.
Sarkar's consideration of a taxonomic measure of difference
between species as part of "biodiversity" echoes the
popular objects and differences strategy.



Possible proposals to include aspects beyond richness (counting units)
seem limitless. This problem highlights the advantages of a simpler
framework where "biodiversity" focuses on the number of
units, while recognising that the same units can be part of numerous
other calculations that include standard ecological indices. Thus,
complementarity, endemism, and dissimilarities and many traditional
ecological "diversity" measures all can be calculated, but
they are not measures of "biodiversity".


### 2.4 How understanding variety helps us build a working calculus of biodiversity



The framework based on counting-up units contrasts with other
proposals for general frameworks for biodiversity, including those
proposals that have attempted to include a variety of
calculations--endemism, dissimilarity, rarity, etc.--within
the definition of biodiversity (see below). The framework based on
counting-up units implies not only that biodiversity as variety is
that total count, but also that we can carry out lots of other
important, associated, calculations that will be useful for
decision-making and policy--notably looking at gains and losses.
This idea of a biodiversity "calculus" contrasts with the
ecologically oriented perspective that there are many different
indices called "biodiversity".



One important companion calculation is called
"complementarity" (Kirkpatrick 1983)--the gains and
losses in biodiversity as objects are gained or lost. While
biodiversity is quantified by an inferred count of number of different
units, decision-making about biodiversity uses various calculations
based on those units. Complementarity usefully indicates marginal
changes--the number of units lost, or the increase in the number
represented by an added protected area. Faith (1994) focussed on
complementarity as an example of useful calculations (referred to as
"components of biodiversity") based on inferred counts of
units:



> 
> 
> The problem of prioritising areas illustrates how pattern
> (specifically environmental pattern) can be used as a surrogate for
> biodiversity, in predicting the same components of biodiversity that
> would be used at the species level directly, notably
> complementarity.
> 
> 
> 



The approach using environmental pattern for such calculations can be
generalised to cover other patterns to make inferences about
underlying units. For PD, the pattern is phylogeny and a
species' complementarity reflects the relative number of
additional features contributed by that species. PD decision-making
sometimes uses calculations that are integrated with species'
estimated extinction probabilities--extending the idea of
complementarity to "expected" loss. Priorities for
conservation efforts for endangered species then can respond both to
degree of threat and to amount of potential loss of PD. One such
conservation program is the EDGE of Existence program
("evolutionarily distinct and globally endangered"; see
the link in
 Other Internet Resources).



By recognising other calculations as useful, but not equated with
"biodiversity", and by side-stepping the weaknesses of the
objects-differences framework, we can focus on counting-up different
units, and focus on the value of having many different units. Thus,
the idea of a useful calculus further reinforces the role of
biodiversity-as-variety in providing option and insurance values.



This perspective is relevant to the second part of the IPBES
definition of biodiversity (above), where "biodiversity"
is to include various measures of "change" in
distribution, abundance etc. This perhaps reflects the ecology
perspectives in which "biodiversity" is equated with
various ecological indices and calculations, such as dissimilarity or
relative abundance. Sometimes it is not at all clear how the key idea
of "biodiversity loss"--complementarity--applies
in such cases. This issue is addressed further in the section below on
ecology and ecosystems framings.


## 3. Beyond Variety--Post 1985 New "Biodiversity" Framings



The IPBES definition illustrates the trend to include many other
biotic/ecological aspects in the definition. Popular encyclopedia
entries on "biodiversity" and major reviews illustrate how
this trend has contributed to definitional chaos. In the
*Encyclopedia of Biodiversity*, Swingland argues "An
unequivocal, precise, and generally accepted definition of
biodiversity does not exist". in the *Routledge Handbook of
the Philosophy of Biodiversity*, nearly every chapter discusses
the "biodiversity" definition problem. The SEP entry
supplement
 biodiversity preservation under environmental ethics
 laments "A persistent complication is that there continues to
be no single agreed measure of biodiversity".



Koricheva and Siipi (2004) observe that



> 
> 
> biodiversity still lacks a universally agreed upon definition and is
> often redefined depending on the context and the author's
> purpose.
> 
> 
> 



They suggest that:



> 
> 
> Such great terminological variation is understandable, since concerns
> for biodiversity relate to several realms of human practice, including
> conservation, management, economics, and ethics, and thus give rise to
> different "discourses". (2004: 28)
> 
> 
> 



The common measure, species richness, illustrates the different
perspectives. The pre-history of biodiversity, reflecting the species
extinction crisis and the values of variety, provides a core rationale
for a definition that includes counting-up species. In contrast,
Koricheva and Siipi (2004) argue that popularity of species richness
(as a measure) continues simply because it is understandable,
measurable, and it uses available information (see also Sarkar 2019).
A section below ("the Conservation Biology framing")
returns to this issue, in considering a perspective that assumes that
the "biodiversity" concept arose as part of the new
discipline of conservation biology in the mid-1980s.



The pre-history of "biodiversity" also highlighted the
idea that the value of variety itself should be considered along-side
the recognised benefits (and dis-benefits) of individual species
("biospecifics"), and all these benefits/values can enter
into trade-offs and synergies that support decision-making. Some
current perspectives or framings about biodiversity and its value can
be understood as again blurring that distinction between biodiversity
and "biospecifics". One such framing equates
"biodiversity" with all of nature. A focus on
"biodiversity" as the collection of individual
units/elements suggests that "biodiversity" covers so many
individual elements that it more or less can be equated with biotic
"nature". An ecological/ecosystem framing of biodiversity
expands this further--"biodiversity" may be
interpreted as including not only the many individual elements but
also all their ecological interactions, and associated processes.
These expanded perspectives, focused on elements and their
interactions, create a risk that we may miss the opportunity to
properly consider both values of nature/ecology and the values
associated with biodiversity-as-variety.



Several factors may help to explain the current wide range of
perspectives about biodiversity's definition and values. One is
the idea that the term "biodiversity" was intended to
capture everything we wish to conserve within the discipline of
conservation biology. Another is the idea that
"biodiversity" only gains meaning and importance to
humanity in supporting ecosystem functions and services. Both of these
framings are supported by particular interpretations of the history of
the concept. More recently, another emerging perspective is a call for
a re-casting of the term "biodiversity" to make it more
holistic in reflecting socio-ecological thinking. The themes outlined
above roughly correspond to three kinds of re-framings of
"biodiversity", defining the next three sections below:
 SS4 the ecology/ecosystem services framings,
 SS5 the conservation biology framing, and
 SS6 socio-ecological framings.


## 4. The Ecology/Ecosystem Services Framings



"Ecosystem services" are all the benefits that humanity
derives from ecosystems (Daily 1997). While that term is probably
younger than the term, "biodiversity", it not only has its
own pre-history (as "natural services" from nature; see,
e.g., Holdren & Ehrlich 1974), but also shares a pre-history with
"biodiversity". This history reveals early ideas about how
aspects of biotic diversity are important to maintaining the
ecological functions that support ecosystem services. These
discussions drew upon the long tradition in ecology to use various
ecological indices--broadly referred to as
"diversity" indices--and so inviting equation with
the new term "biodiversity". Exploring this connection
between biotic diversity, ecological functions, and services has
become a massive research venture over the past 25 years (for review,
see, e.g., Gomez Baggethun et al. 2010). The name of the
international platform for biodiversity, "Intergovernmental
Platform on Biodiversity and Ecosystem Services" (IPBES),
reflects this active, high-profile, connection.



The ecosystem services framing of "biodiversity"
interprets the many aspects of "diversity" that link to
functions and services as part of a "biodiversity"
narrative. This narrative is interpreted as the basis for a rationale
for conserving biodiversity, because it is claimed to link
biodiversity, for the first time, to benefits for humanity.


### 4.1 Further exploration of biodiversity insurance value



The insurance and options benefits from living variation recognised in
the pre-history, also appear in later work, using the new term
"biodiversity" (e.g., Bartkowski 2017). Post 1985, such
discussions continued to follow the pre-history in considering the
value of variety itself for insurance. However, alternative
perspectives focussed more on the early discussions pointing to a
broader ecological/ecosystem interpretation of insurance and related
ideas such as "ecological integrity".



IUCN (1980) described "ecological integrity" as:



> 
> 
> Maintaining the diversity and quality of ecosystems and enhancing
> their capacity to adapt to change and provide for the needs of future
> generations.
> 
> 
> 



Sometimes this more ecological rationale has been discussed as part of
a new "biodiversity" framing, so setting the stage for
ecological definitions of "biodiversity".



For example, Ehrlich and Wilson (1991) listed three basic reasons why
we should care about biodiversity. The first was most closely linked
to intrinsic value: a "moral responsibility to protect what are
our only known living companions in the universe". Their second
reason reflected the option value of biodiversity--the idea
that



> 
> 
> humanity has already obtained foods, medicines, and industrial
> products and other benefits from biodiversity, and has the potential
> for many more.
> 
> 
> 



Their third reason was an insurance type argument, based on the
recognised ecosystem services provided by natural ecosystems. Here,
they made a link to biodiversity in arguing that "diverse
species are the key working parts" within such ecosystems.



"Working parts" could mean variety, or it could refer to
the ecology of lots of parts in an ecosystem. In earlier work (Ehrlich
& Ehrlich 1981) "insurance" was linked to the loss of
biological diversity and so linked to variety. Ehrlich and
Ehrlich's (1992: 219) later arguments for biodiversity
conservation referred both to option value (from variety expressed as
nature's "genetic library"), and to insurance
value--expressed less as variety and more as a consideration of
ecological aspects. Thus, "insurance" sometimes joins
"ecological integrity", and similar terms as part of a
storyline about many relevant aspects of ecosystems.



Similarly, the Millennium Ecosystem Assessment (2005) described the
multiple values of biodiversity in a way that reinforced the duality
of insurance and option values from variety, but also linked
"biodiversity" to ecological aspects, including resilience
and integrity.


### 4.2 The rationale for the ecosystems framing



The ecosystem services framing builds on the important idea that
ecosystems provide many, often under-appreciated, benefits to people
(clean water, useful resources, etc). It is natural to consider that
these benefits provide a case for conservation of
"biodiversity". The ecosystems framing adopts the
perspective that it is "biodiversity"--typically,
interpreted broadly as ecological "diversity"--that
is the basis for these important functions and services. This framing
reduces the focus on variety of species or other elements (in the
sense of counting-up). Perhaps because of the natural
within-ecosystems focus, this also has amounted to lesser emphasis on
global scale option value from such variety. The ecosystems framing
reflects this perspective in the range of "biodiversity"
definitions considered. The idea that "biodiversity" is
important for ecosystem services is given support by defining
"biodiversity" in terms of those ecological factors that
are important for ecosystem services.


### 4.3 Definitions and values



Noss (1990) regarded biodiversity as including composition, structure,
and function, reflecting the range of "diversity" measures
in ecology (ecological diversity indices are reviewed in Koricheva
& Siipi 2004). The CBD's use of the general term,
"diversity" (see above) has provided a broad canvas for
interpretation of "biodiversity" in a framing focussed on
ecosystems. The now popular ecological definitions of
"biodiversity" are exemplified in the *Routledge
Handbook of Ecosystem Services*:



> 
> 
> Biodiversity broadly encompasses the number, abundances, functional
> variety, spatial distribution, and interactions of genotypes, species,
> populations, communities, and ecosystems. (Balvanera et al. 2016:
> 46)
> 
> 
> 



Diaz et al. (2009: 55) describe "biodiversity"
as



> 
> 
> the number, abundance, composition, spatial distribution, and
> interactions of genotypes, populations, species, functional types and
> traits, and landscape units in a given system.
> 
> 
> 



Mace, Norris, and Fitter (2012) argued that the definition of
"biodiversity" "embraces many alternative diversity
measures" (see also Hillebrand et al. 2018), and highlighted
"biodiversity" as species composition: "the
composition of biological communities in the soil" is an example
of how "biodiversity is a factor controlling the ecosystem
processes that underpin ecosystem services" (2012: 22).



This broad use of diversity measures recalls early work linking
various ecological diversity indices to "stability" and
other desirable aspects of ecosystems (for review, see the SEP
 ecology
 entry). In the ecosystems framing, "biodiversity
services" are defined in terms of ecological processes:



> 
> 
> Biodiversity is structured by a range of ecological processes
> ....These processes--which can be termed "biodiversity
> services"--underpin and determine the stability,
> resilience, magnitude and efficiency of the functions and properties
> of ecosystems. (Seddon et al. 2016: 7)
> 
> 
> 



This characterisation neglects the previous use of this same term to
refer to global biodiversity option value (see Faith 2018b).
Similarly, Norton (2001) pointed to increased emphasis on processes
that under-pin ecological "health" or
"integrity", and de-emphasis of a conventional
elements-oriented perspective for biodiversity.



These ecological definitions of "biodiversity" have
influenced some perspectives about biodiversity values. The
*Encyclopedia of Biodiversity* chapter on "The Value of
Biodiversity" (Dasgupta, Kinzig, & Perrings 2013: 168),
reflects the ecosystems framing in claiming that:



> 
> 
> The value of biodiversity derives from the value of the final goods
> and services it produces. To estimate this value, one needs to
> understand the "production functions" that link
> biodiversity, ecosystem functions, ecosystem services, and the goods
> and services that enter into final demand.
> 
> 
> 



"Option value" is mentioned in the chapter, but is linked
to a "resource", not to variety itself.



This framing is reflected also in the 2019 review, "The Economic
Value of Biodiversity", by Hanley and Perrings. It focuses on
ecosystem services, and does not mention the investment value of
biodiversity-as-variety. Similarly, in the *Encyclopedia of
Biodiversity* chapter on "Sustainability and
Biodiversity" (Cavender-Bares et al. 2013: 73), the value of
biodiversity is based on its relationship to ecosystem functions, and
their value of in terms of human well-being. Thus, the ecosystems
framing tends to focus on within-ecosystem values and tends to ignore
global values including option value.



A core perspective in this framing is that "biodiversity"
is about critical ecological elements:



> 
> 
> A major criticism of the valuation approach to conserving biodiversity
> is that current understanding of the mechanistic links between species
> and the functioning and resilience of ecosystems is far from
> complete.... Without this, we may fail to protect those elements
> of diversity crucial for ecosystem integrity. (Seddon et al. 2016)
> 
> 
> 


### 4.4 History



A within-ecosystems focus, and typical neglect of global biodiversity
option value, sometimes has been supported by an accounting in which
"biodiversity" historically had been recognised as all
about intrinsic value, until the ecosystem services framing forged
links for the first time to anthropocentric values (for discussion,
see Faith 2018b).



The rationale for the ecosystem services framing presents two
principal approaches to conservation:



> 
> 
> Caricaturing slightly, the first is focused on biodiversity
> conservation for its own sake, independent of human needs or desires.
> The second is focused on safeguarding ecosystem services for
> humanity's sake: for the provision of goods, basic life-support
> services, and human enjoyment of nature. (Balvanera et al. 2001:
> 2047)
> 
> 
> 



The ecosystems framing sees the ongoing loss of biodiversity as a
values failure that calls for a shift to ecosystem services
values:



> 
> 
> Despite appeals about the intrinsic value of nature and important
> gains in some areas, the dominant flow of human activity has continued
> moving in directions detrimental to biodiversity conservation ...
> In response, some within the conservation community have attempted to
> broaden the base of support for biodiversity conservation by adopting
> the concept of ecosystem services and by arguing that the conservation
> of biodiversity matters not only because of its intrinsic value but
> because it is essential for human well-being. (Reyers et al. 2012:
> 503)
> 
> 
> 



Thus, in this historical accounting the ecosystems framing forged the
first links from "biodiversity" to anthropocentric
values.



A popular history of ecosystem services (Gomez Baggethun et al.
2010) similarly presents the original motivation for considering
ecosystem services as helping biodiversity conservation:



> 
> 
> It starts with the utilitarian framing of beneficial ecosystem
> functions as services in order to increase public interest in
> biodiversity conservation (Westman 1977...).
> (Gomez-Baggethun et al. 2010: 1209)
> 
> 
> 



In reality, Westman did not refer to biodiversity (nor "biotic
diversity"). Instead, Westman linked functions to various
aspects of ecology, including "how components of the system
interact" (1977: 961) and "the flow of materials and
energy" (1977: 963).



Customised narratives in the ecosystem framing are apparent also in
Peterson et al.'s (2018: 1) reference to:



> 
> 
> the notion of the "maintenance of options" type of
> nature's contributions to people (NCP 18; Diaz et al.
> 2018), enhancing "the capacity of ecosystems to keep options
> open in order to support a good quality of life" (Diaz et
> al. 2018: SM).
> 
> 
> 



This would seem to make a strong case for a focus on ecosystems, but
Peterson et al. misquote this foundational paper on NCP.
"Maintenance of options" in fact is described (Diaz
et al. 2018: Table S1) as the "Capacity of ecosystems, habitats,
species or genotypes to keep options open in order to support a good
quality of life". The misrepresentation gives the impression
that the maintenance of options is only about how ecosystems support
human-well-being.


### 4.5 Concluding observations



The shift by IPBES away from an ecosystem services framing in favour
of a broader "nature's contributions to people"
(NCP; for discussion, see Diaz et al. 2018, 2019; Faith 2018b)
reflected, in part, the need to better address global/regional
biodiversity values:



It has to be recognized that the concept of "nature's
contributions to people" has evolved in a context where
challenges related to the loss of biodiversity are addressed and
assessed on global and regional levels. The implications of this
widening from the ecosystem service framework ... is largely an
issue that remains to be explored. (IPBES 2018a)



The IPBES regional and global assessments (IPBES 2018b,c, 2019)
advanced this wider conceptual framework through the use of a measure
of biodiversity-as-variety, phylogenetic diversity, as an indicator of
the global status of the maintenance of options (see link to
"Phylogenetic diversity and IPBES" in Other Internet
Resources).


## 5. The Conservation Biology Framing


### 5.1 Introduction



Sarkar (2017: 43) summarises the basis for what might be called the
conservation biology framing of "biodiversity":



> 
> 
> the term "biodiversity" and the associated concept(s) were
> introduced in the context of the institutional establishment of
> conservation biology as an academic discipline....
> 
> 
> 



The SEP
 conservation biology
 entry describes the motivation for a biodiversity framing tied to
this historical link: "in the 1980s, conservation biologists
united and argued that biodiversity should be the focus of the
discipline" which "rests on the value assumption that
biodiversity is good and ought to be conserved". This rationale,
however, was not linked to any clear idea of what
"biodiversity" means:



> 
> 
> conservation biology as a discipline has expended a great deal of
> intellectual effort in articulating exactly what is its object of
> study and has settled on biodiversity as the answer. However, there is
> a debate concerning what biodiversity is....
> 
> 
> 



Here, the stated rationale is that "biodiversity" is
normative and is the focus of the discipline, but there is no
reference to the pre-history discussions of a normatively relevant
definition of biodiversity as variety.



The review of the development of the conservation biology, by Meine,
Soule, and Noss. (2006), does trace some historical foundations. It
documents the idea of a shift in thinking from individual species
losses to loss of the diversity of life. This shift is described
nicely in comparing two editions (1959 and 1987) of the same book
(Matthiessen 1987)--where the 1987 version introduces new
emphasis on the loss of "the diversity of
 life".[2]



Sarkar (2017) notes that ecological diversity indices were largely
ignored in the early history of conservation biology. In contrast,
Meine, Soule, and Noss. (2006) frequently used the term
"diversity", This perhaps reflected co-author Noss's
(1990) much-cited paper characterising biodiversity as including
composition, structure, and function, which echoes the range of
"diversity" measures in ecology. The unlimited
possibilities of such diversity measures may have contributed to the
difficulty in finding agreement on a single definition of
"biodiversity". The conservation biology framing thus
gains justification in embracing the prospect of
"working-backwards", with the challenge to define
"biodiversity" to capture those aspects of
biological/conservation normative value.



How then is "biodiversity" to be defined under these
assumptions? The next two sections review the important discussions
about the definition of biodiversity, and the later arguments that the
definitional problems mean that the term "biodiversity" is
counter-productive and should be abandoned.


### 5.2 Biodiversity deflationism



"Biodiversity deflationism" emphasises the role of the
biodiversity concept in conservation practice. Deflationists consider
biodiversity as "what is conserved by the practice of
conservation biology" (Sarkar 2002: 132). Unlike other framings
of biodiversity, biodiversity is operationally defined, there is no
semantic definition, just an output from the practice of
conservation.



The practice of conservation biology should, within this view, be
systematic conservation planning (Sarkar & Margules 2002). What is
being conceptualised as biodiversity is revealed by this activity.
This decision procedure involves using algorithms to identify a
conservation area network; a conservation area that best optimises the
interests of local stakeholders. Local stakeholders, people with an
interest in that land, decide what features they want to prioritise.
While stakeholder can have a wide range of interests in this land,
they must include "biodiversity constituents" or
"true surrogates" (Sarkar 2005, 2012). These describe the
biotic features that the procedure maximises. "Biodiversity
constituents" might appear to largely overlap with
"biodiversity" in the sense of variety: a list of items,
or measures of variety that describe biological items, which we aim to
preserve. However, these items are not necessarily measuring biotic
variety, as Sarkar includes sacred groves or the Monarch Butterfly
Migration route as constituents of biodiversity. Sarkar stipulates
that biodiversity constituents must satisfy the following conditions:
they must be biological, variability of biotic features must be
represented, taxonomic spread should be represented, these biotic
features should not just be those of material use (Sarkar 2005; 2012).
As such, there are adequacy conditions which guide what the procedure
optimises and, as a result, conserves.



For proponents of biodiversity deflationism, there is no fact of the
matter about what biodiversity is. Biodiversity is irrevocable local
and tied to local values and interests in the natural environment. We
can only infer backwards from what is preserved in the act of
conservation to what convention tends to be described as biodiversity
(Sarkar 2019). Therefore, biodiversity cannot play any role as a
concept outside of the context of local conservation practice. This
has an odd implication. Across biology biodiversity is used as concept
within the science, both for conservation but for other sciences.
Deflationists tend to dismiss biodiversity eliminativists, who want to
ban the use of "biodiversity", as too impractical as it is
a common term in conservation (Sarkar 2019: 378). They, however, limit
"biodiversity" to only conservation practice, claiming
that scientific concepts of biodiversity are irrelevant (Sarkar 2019:
381). Biodiversity does not exist for the use of scientists in
research. Thus, biodiversity conventionalists eliminate biodiversity
from the context of scientific research and claim such research does
not indicate what features we should preserve (see also the section on
 operationalizing biodiversity in the entry on conservation biology).


### 5.3 Biodiversity eliminativism



While biodiversity has been accepted as a core goal of modern
conservation science, there is some scepticism in the philosophical
literature toward the utility of this concept. A series of
philosophers have argued that the biodiversity concept is detrimental
to environmental efforts (Maier 2012; Santana 2014, 2018; Morar,
Toadvine, & Bohannan 2015). These arguments tend to coalesce
around several points: that the biodiversity concept not
operationalizable, biodiversity is not desirable, and that the concept
obscures many of the values people have towards nature. The argument
is that, either the concept cannot be used, or it may be used, but
with recognition that it does not represent our ethical interest in
the environment.



The belief that biodiversity cannot be adequately operationalized has
appeared numerous times through the literature. Some argue that
operationalizing biodiversity requires a "diversity"
measure, or set of measures, both represent the concept of
biodiversity and not be contradictory in its recommendations about
what to conserve. Bryan Norton early on suggested that



> 
> 
> strong arguments show that an index that captures all that is
> legitimately included as biodiversity is not possible. Biodiversity
> cannot be made a measurable quantity. (Norton 2008: 373)
> 
> 
> 



This is because many of the different scientific measures for
biodiversity are incommensurable, clashing with each other. For
example: an area of possessing populations that are highly
functionally distinct may be quite species poor. Some take the
apparent incommensurability of biodiversity measures to show that
measures should be used in context sensitive instances either relative
to the development of conservation science or to the local interests
of stakeholders (Koricheva & Siipi 2004; Sarkar 2005; Maclaurin
& Sterelny 2008). An alternative considered is that we should
narrow down the list of measures to that are most important according
to some desiderata (Maclaurin & Sterelny 2008; Lean 2017; Meinard,
Coq, & Schmid 2019).



Even if "biodiversity" was made to be tractable (in the
sense used above), eliminativists are suspicious of biological
diversity being regarded as valuable. Diversity across different
biological arrangements is even argued to be undesirable. Maier points
to diversity of parasites and diseases being undesirable (Maier 2012).
Diversity sometimes reduces the value of taxa as the rarity of a
species tends to increase its value (Santana 2014). Morar, Toadvine,
and Bohannan (2015) explain this is because it is "not
life's variety but rather life itself" (2015: 24) that is
valuable (without making reference to insurance and options values of
variety). The perception of a mismatch between ethical interests in
the environment and diversity is emphasised by all eliminativists.



Eliminativists believe "biodiversity" has mislead
conservation, as the concept and term was designed to be exhaustive of
human interests in the environment--and it cannot succeed in this
task. The idea that biodiversity was designed to represent all human
values of the environment appears in Maier's work as "the
biodiversity project", Santana argues that biodiversity is just
an intermediary for "ecological value", and Morar,
Toadvine, and Bohannan argue that biodiversity "does not exhaust
what we value in the natural world" (2015: 24). Santana (2014)
provides a clear presentation of this belief and uses it to argue that
biodiversity is a misleading and unnecessary step in conservation
planning. Biodiversity acts in conservation as an intermediary between
all the ways we value the environment and the implementation of
surrogate measures for these values, which are then used in
conservation planning. Santana suggests we should remove the step of
considering biodiversity and directly represent our values in the
environment without considering diversity (see also SEP
 conservation biology
 entry)



This perspective differs from other frameworks for understanding
biodiversity (including the focus on variety, originating in the
pre-history of the term), which consider biodiversity as just one of
several different conservation values which may trade off against each
other (Faith 1995; Norton 2015; Lean 2017). One may choose to
prioritise wilderness, or ecosystem services, over biodiversity and
decision theoretic measures will be used to weight such
considerations.



It is argued by some that biodiversity not only doesn't
represent all the ways the public values nature, it may also hinder
the public's engagement in nature. As a scientific
"proxy" for natures value it is viewed as a dangerous case
of scientism (Morar, Toadvine, & Bohannan 2015; Sarkar 2019). By
having the "veneer of objectivity" it masks the normative
dimension of conservation. The argument is that this can lead to an
attitude of leave it to the scientists and shift the responsibility
away from the policymakers and the public (Morar, Toadvine, &
Bohannan 2015). This is interpreted as representing a dangerous
impediment to the democratic dimension of conservation. This is
regarded as an interesting question for the interface between
conservation theory and public policy.



Eliminativism proposes that there are tensions in the use of the
"biodiversity" concept, posing the idea that there is a
mismatch between the scientific measures of biodiversity and the
normative role it plays in conservation science. This perspective
therefore contrasts strongly with the historical "variety"
framing (above), where the scientific measure of biodiversity as
variety, and its recognised value to humanity, is the source of
normativity
 claims.[3]
 Eliminativists argue that, while it would be hard to remove
"biodiversity" from use in conservation, this is necessary
to allow for a clearer connection between humanities interests in the
environment and conservation practice (also see the section on
 eliminating biodiversity in the entry on conservation biology).


### 5.4 Concluding observations



Sarkar (2019: 375) claims that "the term
"biodiversity" and the associated concept(s)" arose
along with the discipline of conservation biology. This accords with
the deflationist and eliminativist perspectives that the
"biodiversity story" began around 1985, with conservation
biology guiding the conceptual development of
"biodiversity", including its definition and values. This
narrative does not address the earlier conceptual history that had
articulated normative value of living variation, and so it raises the
need for comparisons with that "variationist" framing.



The SEP entry
 conservation biology
 provides some basis for comparisons, in exploring the idea that
conservation biology is all about a still-undefined concept of
"biodiversity". In the entry's section
 what is biodiversity?
 there are no citations of the early discussions from the 1970s, and
so there is perhaps an under-appreciation of the early ideas of
variety as a possible guide to resolving questions of definition. This
relates to the interesting issues raised in this section about how the
concept/definition of "biodiversity" is supposed to cope
with the dis-benefits of some individual species. The challenge
remains to recognise the possible useful distinction between
biodiversity/variety and biospecifics (individual elements).



Consideration of the pre-history of "biodiversity"
suggests that the conservation biology framing has adopted a
story-line that is a disservice to systematics/taxonomy. As noted
above, Sarkar (2017, 2019) follows his claim that the
"biodiversity" term (and concept) were introduced in the
context of the establishment of conservation biology, with the claim
that



> 
> 
> Subsequently, the term and the concept were embraced by other
> disciplines particularly by taxonomists.... as a conduit for
> funding that taxonomists wanted to exploit....
> 
> 
> 



The pre-history, in contrast, reveals how the concept in fact arose
through the work of systematists (e.g., Iltis 1972; Anonymous 1974),
and was followed by calls by Wilson (1985) and others (see above) for
more systematic efforts, in order to fill knowledge gaps (see also
Lean, 2017).



The conservation biology framing highlights individual elements that
are valuable, with less emphasis on variety. For example, Sarkar
argues that conservation logically will focus on "those aspects
of biotic variety that should be conserved. That does not necessarily
include all of natural variety" (Sarkar 2019: 17).
Sarkar's example is revealing:



> 
> 
> The human skin hosts thousands of microbial species though
> interpersonal variability is not as high as in the gut which hosts
> millions... Should we feel an imperative to conserve all the
> microbial diversity on the human skin or gut?
> 
> 
> 



This sounds like a powerful example--who likes germs? The
question in reality reveals an absence of consideration of the
established benefits and values of variety itself. The gut microbial
context is particularly revealing--over the past decade or so,
reductions in an individuals' variety of gut microbes (e.g., as
measured using the PD biodiversity measure) is now associated with
more than a dozen different human diseases. This biodiversity possibly
provides a kind of insurance benefit in healthy individuals (see the
link to "Phylogenetic Diversity and Human Health", in
 Other Internet Resources;
 for other philosophical issues related to microbial biodiversity, see
Malaterre 2017).



A related conceptual disconnect is apparent also in Sarkar's
(2017) claim,



> 
> 
> for a concept of biodiversity that can be used in practice for
> instance in the selection of conservation areas, richness was shown to
> be inadequate in the 1980s.
> 
> 
> 



In contrast, variety or "richness" clearly is the
desirable property of the set of conservation areas, and we use parts
of the biodiversity "calculus" (see above), such as the
complementarity of individual areas, in order to maximise this
property of a nominated set. According to "variationists",
the concept of biodiversity as variety/richness is exactly what is
needed to address the biodiversity crisis (Faith 2017).



Absence of recognition of the historical link between variety and
normativity also suggests contrasts. The idea that
"biodiversity" is the business of conservation biology,
and that biodiversity is good, implies that,



> 
> 
> if there is no adequate normative basis for biodiversity conservation,
> conservation biology becomes a dubious enterprise because its explicit
> purpose is the conservation of biodiversity.
> 
> 
> 



The storyline is that conservation biology is normatively oriented,
and so we have to find a definition of "biodiversity" that
matches that normativity. In contrast, variationists would suggest the
opposite: that "biodiversity" is normatively oriented, and
then we have to find a "conservation biology" that
addresses that normativity. Sarkar concludes that



> 
> 
> how "biodiversity" is defined, that is, what the
> "constituents" of biodiversity are, depends on cultural
> choices about which natural values to endorse for conservation.
> 
> 
> 



As noted above, the constituents of interest can include things like
sacred groves, and processes like annual migration of Monarch
butterflies (Sarkar 2019). Thus, this framing does not recognise
biodiversity-as-variety, and its current benefit and normativity;
instead, it looks for the elements that may be conserved with some
normativity, and calls that "biodiversity".



There seems to have been a logical development of arguments in the
conservation framing--conservation biology was regarded as
normatively all about "biodiversity"--a term
interpreted as having no clear definition, and so to be defined by
whatever conservation might normatively focus on--then arguments
asserted that conservation focuses in practice on lots of things, and
that this was a burden too great for the term. Not yet considered, in
the development of philosophical arguments for the conservation
biology framing, is the possibility that a miss-step was made right at
the beginning--ignoring the preceding long history of
"biodiversity" interpreted as variety, with current
benefit to humanity, and normative import.



Eliminativists want to get rid of the term "biodiversity",
with the claim that this would allow for a clearer connection between
humanity's interests in the environment and conservation
practice. But this is just one of at least three proposed fates for
the problematic term "biodiversity". Those advocating core
biodiversity definitions and values based on variety (call them
"variationists", see also Burch-Brown and Archer 2017),
might advocate adoption of this basic definition, with the claim that
it not only accords best with the extinction crisis and core
anthropocentric values (including insurance and investment), but also
effectively allows trade-offs and synergies with humanity's
other interests.



A third pathway is discussed in the next section--where the fate
of the problematic term "biodiversity" is not to be
eliminativism, nor back-to-basics variationism, but is to be a kind of
"holism"--"biodiversity" expanded in
meaning to cover the whole range of "socio-ecological" or
human-nature links.


## 6. Socio-Ecological Framing



The conservation biology framing interprets "biodiversity"
as a term that is to capture everything we want to conserve. An
emerging socio-ecological framing of biodiversity requires that the
term take on a broader scope--it is to be made operational, not
just for conservation, but more broadly for sustainability,
encompassing the many ways that society and nature are inter-linked.
While conservation biology has interpreted "biodiversity"
as, from the start, all about society's conservation values, the
socio-ecological framing of biodiversity adopts a different narrative.
Here, the claim is that, the term "biodiversity" started
out with a too-narrow, strictly biological, interpretation, and now
should be re-cast to better reflect, in different contexts, what
society values about nature. The term "biodiversity" in
fact appears to wear two different hats in the rationale for a
socio-ecological framing: one of expectation and the other of
disappointment. The expectation is that "biodiversity" is
obliged to capture society's various values and relationships
with nature; the disappointment is based on the claim that in reality
"biodiversity" has been too biotic and creates a
human-nature dichotomy.



The roots of this framing are found in the idea that biodiversity must
reflect society's various environmental concerns. For example,
the book, *Defending Biodiversity* (Newman, Varner, &
Linquist 2017) focusses on philosophical issues about the value of
"biodiversity", because this is seen as the way to
"throw a sufficiently large net over these many different
flavours of environmentalism" (2017: 15). Similarly, Lele et al.
(2018b) take as a starting point the idea that



> 
> 
> The concept of biodiversity currently captures the core of
> naturalists' concerns for the environment, subsuming earlier
> formulations such as wilderness or wildlife. (2018b: 7)
> 
> 
> 



Two recent books summarise these perspectives (*Seeds of Change:
Provocations for a New Research Agenda*, Wyborn, Kalas, & Rust
2019 and *Rethinking Environmentalism: Linking Justice,
Sustainability, and Diversity*, Lele et al. 2018a). In the first,
Diaz (2019: 62) outlines an historical argument that
"biodiversity" has been purely biological in focus, and
therefore needs to be broadened to reflect human links:



> 
> 
> The notion of biological diversity existed as a purely biological
> concept well before the word "biodiversity" emerged"
> and "Faced with the new challenge and desire to be useful to
> society,.... It is now clear that whilst
> "biodiversity" is about the biological realm, its crisis
> and potential solutions pertain to the social, cultural, economic and
> political realm....Broadening the concept of
> biodiversity--from a property of measurable biological systems to
> a socio-ecological boundary object.
> 
> 
> 



Here, "biodiversity" history is presented as involving a
post-1985 new-found desire to be useful to society, where, in
response,



> 
> 
> biological diversity scientists mustered the best tools they had:
> mathematical and statistical models and indices, which required a
> single and simple "currency"--the number of
> species.... (Diaz 2019; see also Sarkar 2019)
> 
> 
> 



This claimed new awareness then sets up the call for a re-casting of
"biodiversity":



> 
> 
> It is now clear that whilst "biodiversity" is about the
> biological realm, its crisis and potential solutions pertain to the
> social, cultural, economic and political realms. Therefore, diverse
> perspectives are needed in reframing biodiversity more broadly. Very
> few would contest this general statement.... (Diaz 2019:
> 62)
> 
> 
> 



This claimed incontestability of the need for a biodiversity reframing
is given support by an historical accounting that omits the rich
history that had forged links to all those "realms" (see
previous sections); anthropocentric insurance and investment values of
biotic diversity (typically the number of species) were recognised in
the context of the extinction crisis, and integrated in policy along
with other needs of society. In contrast, the socio-ecological framing
adopts a new historical accounting, where counting the number of
species was simply a matter of mathematical and statistical models and
indices, which then are found inadequate.



This new historical accounting omits the earlier history that
justifies why biodiversity's definition logically focusses on
variety (or counting units). This omission props up the claim that
even while "biodiversity" is largely biological, it is, at
the same time, ill-defined and confusing. Redford and Mace (2018: 37)
argue



> 
> 
> The lack of clarity over the term simply adds another layer of
> confusion to what is already a complicated and interacting set of
> issues.
> 
> 
> 



Mace (2019: 105) concludes



> 
> 
> Looking back over the past 25 years--roughly the period that the
> Convention on Biological Diversity (CBD) has been in place and the
> term "biodiversity" has been in use--I conclude that
> it has become a confusing
>  term...[4]
> 
> 
> 



In the book, *Rethinking Environmentalism: Linking Justice,
Sustainability, and Diversity*, Redford and Mace (2018) reinforce
this interpretation of "biodiversity" as having only a
recent history, with confusing definitions, and with little link to
human concerns. This is seen as calling for the alternative
socio-ecological framing, in which biodiversity conservation is seen
as "inextricably linked to a living political discourse"
so that a re-cast "biodiversity" can be defined "as
including human beings" (2018: 33). Similar arguments are found
in Koricheva and Siipi's (2004) discussion of biodiversity as
"a social and political construct", compared to a purely
scientific concept (see also the advocacy, by Meinard, Coq, &
Schmid 2019, of "biodiversity practices" rather than
"biodiversity").



Pascual (2019) describes this framing as an "integrated
socio-ecological" perspective where "biodiversity"
is variously socially constructed. In this framing,



> 
> 
> The ways we perceive and relate to biodiversity and make sense of it
> are influenced by collectively constructed and socially shared
> cognitive frameworks. (2019: 129)
> 
> 
> 



Arguments for such a biodiversity re-casting have used the
"people and nature" narrative (Diaz 2019). Mace
(2014: 1559) describes the "people and nature" perspective
as requiring



> 
> 
> metrics that link nature to human well-being, explicitly identifying
> benefits needed and received by people ... the science has moved
> fully away from a focus on species and protected areas and into a
> shared human nature environment, where the form, function,
> adaptability, and resilience provided by nature are valued most
> highly.
> 
> 
> 



The rationale for rejecting the idea of "biodiversity" as
a counting up of species (or other units) employs an argument that



> 
> 
> biodiversity science can become quite reductionist and focussed on
> describing, defining, measuring and counting certain units of life.
> (Mace 2019: 105)
> 
> 
> 



Mace concludes that



> 
> 
> This aspect of biodiversity science to do with metrics has been
> important and influential, but curiously often somewhat disconnected
> from the global change and sustainability agenda. Important as it is
> this is, surely it is too narrow a focus for a biodiversity science
> that will support sustainability. (2019: 106)
> 
> 
> 



This claim again highlights how the narrative in this socio-ecological
framing sees "biodiversity" not only as obliged to capture
sustainability, but also, in its present biological form, a
disappointment in not being connected to humans.



Martin, McGuire, and Sullivan (2013: 125) similarly characterises
"biodiversity" as problematical in being "distinct
from other environmental phenomena, as well as from human
activity". They argue that such separation



> 
> 
> may engender profoundly "unecological" thinking, by
> disassembling life's entities both from each other and from the
> complex environmental contexts necessary for sustenance at all
> scales.
> 
> 
> 



This dissatisfaction with counting-up units or items is echoed also in
philosopher Elliot's (2019) argument that
"biodiversity" has failed to convince people to address
environmental problems. He argues that that we need to "develop
new conceptual schemes that link humans with their
environments", by



> 
> 
> focusing less on specific items in the natural world that we want to
> maintain and more on developing resilient and sustainable systems that
> facilitate the myriad relationships between humans and nature. (2019:
> 68)
> 
> 
> 



These perspectives within the socio-ecological framing suggest
overlaps with the ideas of the conservation biology framing (though
there appears to be little cross-citation). Significantly, both
portray "biodiversity" as in need of some kind of
re-casting, and both see the different ways in which society values
nature as providing guidance about how we should interpret
"biodiversity" in any given context. At the same time,
core differences in the two framings remain: in one,
"biodiversity" has a working biological definition, but is
not connected to society's values; in the other,
"biodiversity" is connected to society's
(conservation) values, but we have no working definition.


## 7. Concluding Observations



A survey of the different perspectives about biodiversity's
definition and its values suggests new challenges for a coherent
philosophy of biodiversity. For example, there has been little work
recognising and reconciling two contrasting perspectives. In the
"variationist" perspective, biodiversity-as-variety, is
justifiably "biological", and is normatively relevant; it
enters broader sustainability practice through trade-offs and
synergies with other needs of society. In the
"socio-ecological" perspective, "biodiversity"
is too "biological", with no normativity, and it fails us
if it is not re-cast to capture as a term all of the things that
concern society within the global change and sustainability
agenda.



There has been little cross-fertilisation among the three framings
(variationist, conservation biology, and socio-ecological). The
challenge ahead is to reconcile some strikingly different
perspectives:


1. "biodiversity" as biological (variation), and the
benefit of variety as having normative importance,
2. what is conserved as having normative importance, and the meaning
of "biodiversity" obliged to capture all that,
3. "biodiversity" as purely biological, and so needing a
re-casting to gain normative status.



Challenges along the way will relate to the need to clarify
distinctions between "biodiversity" as a property of a
set, and "biodiversity" as a reference to that collection
of units, where values of "biodiversity" then might refer
to values of individual units or elements. For example, Pascual (2019:
129) used "nature" and "biodiversity"
interchangeably, and this seems to have reflected a core interest in
society's values for "aspects" of biodiversity (not
variety itself):



> 
> 
> Valuation should therefore be about recognising and learning how to
> bridge distinct values of different people for different aspects of
> biodiversity.
> 
> 
> 



When we start listing valued "aspects", it is not
surprising that this can be considered to be all-of-nature. However,
we must ask: does this miss the opportunity to consider both the
(often global) value of variety itself, and the (often local) value of
favourite "aspects"?



A sense of history (and pre-history) may provide an important lens for
synthesis across different perspectives. The IPBES (2019) Global
Assessment reported that one million species may be at risk of
extinction. Compare that to a report 40 years earlier, headlined,
"The Threat to One Million Species" (Norman 1981).
Significantly, both reports highlighted how the threat of extinctions
is a potential loss of variety and future options for humanity.
However, in the more recent reporting, this message is just one of
many storylines in a complex, overwhelming, "biodiversity"
narrative. This tangle of different storylines suggests that we now
also face a "second biodiversity crisis" (Faith 2019), in
which "biodiversity" has become a malleable term that is
shaped and re-shaped to serve various scientific and policy agendas.
The fate of "biodiversity" (the term) may have a lot to
say about the fate of "biodiversity" (the variety of
life).



A philosophy of "biodiversity" therefore still faces
challenges at the most basic levels of definitions, values, and
history. This calls out for synthesis of ideas, with equal attention
to the fashionable new ideas and the (sometimes) unfashionable older
ideas.