Biodiversity indicators: the choice of values and measures

doi:10.1016/S0167-8809(03)00072-0

Agriculture, Ecosystems & Environment

Volume 98, Issues 1–3, September 2003, Pages 87-98

https://doi.org/10.1016/S0167-8809(03)00072-0 Get rights and content

Abstract

Ideally, an indicator for biodiversity is a linear correlate to the entity or aspect of biodiversity under evaluation. Different motivations for assessing entities or aspects of biodiversity lead to different value systems; their indicators may not correlate at all. For biodiversity evaluation in agricultural landscapes, three indices are proposed, each consisting of a basket of concordant indicators. They represent the three value systems “conservation” (protection and enhancement of rare and threatened species), “ecology” (ecological resilience, ecosystem functioning, based on species diversity), and “biological control” (diversity of antagonists of potential pest organisms). The quality and reliability of commonly used indicators could and should be tested with a three-step approach. First, the motivations and value systems and their corresponding biodiversity aspects or entities have to be defined. In a time consuming second step, a number of habitats have to be sampled as thoroughly as possible with regard to one or several of the three value systems or motivations. The third step is to test the linear correlations of a choice of easily measurable indicators with the entities quantified in the second step. Some examples of good and bad correlations are discussed.

Section snippets

Who needs biodiversity indicators?

National and regional agencies for nature conservation, agriculture, and forestry have to monitor species diversity or other aspects of biodiversity, both before and after they spend tax money on subsidies or ecological compensation management, with the aim of enhancing biodiversity (European Community, 1997, Ovenden et al., 1998, Wascher, 2000, Kleijn et al., 2001). Similarly, international, national or regional non-governmental organisations (NGOs) may want to monitor aspects of biodiversity

Why is it so difficult to reach a consensus on the use of biodiversity indicators?

The complexity of all the aspects of the term biodiversity is illustrated in Fig. 1. It is obvious that no single indicator for biodiversity can be devised. Each aspect of biodiversity requires its own indicator. The difficulties for reaching a consensus on the use of biodiversity indicators are manifold. They imply differing choices for values and measures, which will be discussed here more in detail.

Terms such as biodiversity, indicator or index are not well defined and their use varies

Indicator FOR or FROM biodiversity?

A first major source of misunderstanding is, whether biodiversity itself is to be indicated, or whether certain components of biodiversity are used as indicators for something else. Until 1990, the search for bioindicators had focussed on indicators of “environmental health” or ecological processes such as disturbance, human impact, environmental or global change (Hellawell, 1986, Spellerberg, 1991, Meffe and Carroll, 1994, Dufrene and Legendre, 1997). After the world-wide launch of the term

Alpha-diversity, or contribution to higher scale biodiversity?

A second major dichotomy in the value system for biodiversity indicators is the question of whether the species (or allele, or higher taxon unit) diversity of a given area is to be indicated (local, regional or national level), or if the contribution of the biodiversity of that area to a higher scale surface area (regional, national, global) is important.

In the first case (alpha-diversity, e.g. species richness of an ecological compensation area), an indicator ideally has to be a linear

Indicator for what aspect of biodiversity?

After agreement on indicators FOR biodiversity, and a decision between “alpha-diversity” and “contribution to higher scale biodiversity”, there is still potential for disagreement on “what is biodiversity?” (Gaston, 1996c). In practice, in a majority of cases, species are “the units of biodiversity” (Claridge et al., 1997). However, species diversity can be measured as simple number of species, usually of selected groups of organisms, or species richness may be combined with the evenness of the

Value systems

People involved in developing or using biodiversity indicators are influenced by their personal and/or professional goals. They all may want to measure or monitor biodiversity, but they address different aspects of it. Their focus depends on their motivation for dealing with biodiversity. In an agricultural context, and in an industrialised country in Europe, the three most important motivations to enhance biodiversity are

1.
Species conservation (focus on rare and endangered species).
2.
Ecological

Several steps are necessary

The most accurate indicators of biodiversity are proven linear correlates of the entity or aspect of biodiversity being evaluated. McGeoch (1998) proposed a nine-step approach for selecting bioindicators among terrestrial insects. Basically, the whole procedure can be separated into three steps. The first step is to define the aspect or entity in as quantifiable a way as possible. The second step is to actually quantify that aspect or entity in a statistically reliable number of cases. The

The dilemma of indicating complexity with simple measures

Large environmental monitoring programmes usually avoid using invertebrates for their indicators, although these constitute by far the largest portion of measurable biodiversity. To cut down on effort and costs, measurement of the immense richness and quantity of invertebrates has to be reduced to an optimised selection of taxa. The proposed three-step approach allows for testing all kinds of indicators for their correlation with aspects of biodiversity. The search for linear correlates of

Conclusions

There is no single indicator for biodiversity. The choice of indicators depends on the aspect or entity of biodiversity to be evaluated and is guided by a value system based on personal and/or professional motivation. Each biodiversity index for a particular value system should consist of a basket of methods with one or several concordant indicators. In order to achieve greater reliability and a broader acceptance, indicators have to be tested for their linear correlation with a substantial and

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Biodiversity indicators: the choice of values and measures

Abstract

Section snippets

Who needs biodiversity indicators?

Why is it so difficult to reach a consensus on the use of biodiversity indicators?

Indicator FOR or FROM biodiversity?

Alpha-diversity, or contribution to higher scale biodiversity?

Indicator for what aspect of biodiversity?

Value systems

Several steps are necessary

The dilemma of indicating complexity with simple measures

Conclusions

Agric. Ecosyst. Environ.

Pedobiologia

For. Ecol. Manage.

For. Ecol. Manage.

Biol. Conserv.

Biodiversity indicators in semiarid, agricultural Western Australia

Pacific Conserv. Biol.

Using higher-taxon richness as a surrogate for species richness. I. Regional tests

Proc. R. Soc. Lond. B

Diversity, disturbance and sustainable use of Neotropical forests: insects as indicators for conservation monitoring

J. Insect Conserv.

Estimating terrestrial biodiversity through extrapolation

Phil. Trans. R. Soc. Lond. B

Rapid assessment of biodiversity using biological diversity technicians

Aust. Biol.

Indicator taxa in invertebrate biodiversity assessment

Mem. Mus. Victoria

Plant–insect communities and predator–prey ratios in field margin strips, adjacent crop fields, and fallows

Oecologia

Sampling pasture carabids with pitfalls: evaluation of species richness and precision

Med. Fac. Landbouww. Rijksuniv. Gent

In search of the best correlates for local organismal biodiversity in cultivated areas

Biodivers. Conserv.

Comparative sampling methods for grassland spiders

Bull. Br. Arach. Soc.

Species assemblages and indicator species: the need for a flexible asymmetrical approach

Ecol. Monogr.

Environmental diversity: on the best-possible use of surrogate data for assessing the relative biodiversity of sets of areas

Biodivers. Conserv.