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Biodiversity indicators: The choice of values and measures

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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.
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Agriculture, Ecosystems and Environment 98 (2003) 87–98
Biodiversity indicators: the choice of values and measures
Peter Duelli, Martin K. Obrist
Swiss Federal Research Institute WSL, Zürcherstrasse 111, CH-8903 Birmensdorf-Zürich, Switzerland
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.Theyrepresentthethreevaluesystems“conservation”(protectionandenhancementofrareandthreatenedspecies),
“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.
© 2003 Elsevier Science B.V. All rights reserved.
Keywords: Biodiversity; Indicator; Arthropods; Correlate
1. Who needs biodiversity indicators?
National and regional agencies for nature conserva-
tion, agriculture, and forestry have to monitor species
diversity or other aspects of biodiversity, both before
and after they spend tax money on subsidies or eco-
logical 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 at different levels
and scales (Reid et al., 1993; IUCN, 1994; Cohen
and Burgiel, 1997). In scientific research biodiversity
Corresponding author. Tel.: +41-1-739-2376;
fax: +41-1-739-2215.
E-mail address: peter.duelli@wsl.ch (P. Duelli).
indicators can be used as quantifiable environmen-
tal factors. Since the biodiversity of even a small
area is far too complex to be comprehensively mea-
sured and quantified, suitable indicators have to be
found.
Those who are responsible for comparing and eval-
uating biodiversity have a strong incentive to choose a
scientifically reliable and repeatable indicator, which
inevitably increases costs. The financing agencies usu-
ally opt for a financially “reasonable” approach, which
often results in programmes addressing only essential
work. The resulting compromises make optimisation
of the choice of biodiversity indicators and methods
of fundamental importance.
A recent international electronic conference on bio-
diversity indicators (http://www.gencat.es/mediamb/
bioind, 2000) has revealed widely differing views on
why and what to measure and quantify.
0167-8809/$ – see front matter © 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0167-8809(03)00072-0
88 P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98
Fig. 1. Provisional domain tree of biodiversity based on the survey of 125 text documents in English (Kaennel, 1998). Concepts used by various authors to define biodiversity
are in square boxes, related concepts in rounded boxes. Type and direction of conceptual relationships are indicated by arrows. Synonyms and quasi-synonyms are in italics.
P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98 89
2. Why is it so difficult to reach a consensus on
the use of biodiversity indicators?
The complexity of all the aspects of the term bio-
diversity 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 between different
countriesand disciplines. Dismissing researchfindings
or scientific reports simply on the grounds of differing
views on the use of particular terms (semantic discrim-
ination) would be counterproductive, but study reports
must clearly state what is meant by the terms used. A
helpful review on indicator categories for bioindica-
tion is given by McGeoch (1998).
In this paper, the term indicator is used in the sense
of any measurable correlate to the entity to be as-
sessed: a particular aspect of biodiversity.
The most promising and convincing indicators of
biodiversity are measurable portions of the entity
that we consider to represent a target aspect of bio-
diversity. The term index is used here in the sense
of a scaled measure for one or several concordant
indicators.
3. Indicator FOR or FROM biodiversity?
A first major source of misunderstanding is, whether
biodiversity itself is to be indicated, or whether cer-
tain components of biodiversity are used as indica-
tors for something else. Until 1990, the search for
bioindicators had focussed on indicators of “envi-
ronmental 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 biodiversity
at the Rio Convention in 1992, there was a sudden
and drastic shift in the published literature towards
the search for indicators of biodiversity itself (Noss,
1990; Gaston and Williams, 1993; Gaston, 1996a;
Prendergast, 1997). Since then, however, the term
biodiversity has sometimes been used to allude to or
indicate some aspect of environmental quality.
If a species or a group of species is a good indicator
for lead contamination, it may not indicate biodiver-
sity, i.e. there may not be a linear correlate to biodi-
versity. It is fundamentally a contamination indicator,
or an environmental indicator (McGeoch, 1998) rather
than a biodiversity indicator.
However, “real” biodiversity indicators may be
needed to measure the impact of e.g. lead contami-
nation on biodiversity itself (indicator FOR biodiver-
sity). Such an assessment is different from measuring
the impact of lead on a selected taxonomic group,
which had been chosen because it is especially sensi-
tive to lead poisoning (indicator FROM biodiversity).
4. 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 rich-
ness of an ecological compensation area), an indicator
ideally has to be a linear correlate to the biodiversity
aspect or entity of the surface area in question. Each
species has the same value.
In the second case, the value of the measurable units
of biodiversity (alleles, species, ecosystems) depends
on their rarity or uniqueness with regard to a higher
level area. A nationally rare or threatened species in
a local assessment has a higher conservation value
than a common species, because it contributes more
to regional or national biodiversity than the ubiqui-
tous species. Thus a biodiversity indicator in the latter
case not only has to count the units (alleles, species,
ecosystems), but it has to value them differently and
add the values.
The best known examples are red list species. For
measuring alpha-diversity, they are not given a value
that is greater than any other species in a plot or trap
sample, but for measuring the conservation value of a
plot, their higher contribution to regional, national, or
90 P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98
even global biodiversity has to be recognised. Raised
bogs are notorious for their poor species richness,
but if only a few raised bogs are left within a coun-
try, the few characteristic species present in a “good
bog” are of very high national importance. The prob-
lems of estimating complementarity or distinctness
are addressed e.g. by Colwell and Coddington (1994)
and Vane-Wright et al. (1991), endemism and spatial
turnover by Harte and Kinzig (1997).
This dichotomy between “species richness” and
“conservation value” is the most fervently debated
issue among applied biologists concerned with biodi-
versity indicators, and a recurrent source of misunder-
standings. It will be elaborated further in the chapter
on value systems.
5. Indicator for what aspect of biodiversity?
After agreement on indicators FOR biodiversity,
and a decision between “alpha-diversity” and “con-
tribution 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 abundance distribution of the
species. The best known indices are the Shannon in-
Fig. 2. “Which of the two populations do you consider to have a higher biodiversity?” A choice test for biodiversity evaluation regularly
offered by the first author to students and at public lectures. For the vote, only the upper part without text is shown.
dex, the Simpson index and Fisher’s alpha (Magurran,
1988). Recent observations (Duelli, unpubl.) have
shown that when undergraduate biodiversity students
in entomology lectures have to choose which of the
two communities shown in Fig. 2 (without seeing the
text below them) they consider to be more diverse,
more than half of them decide for the left popula-
tion, because they consider evenness to be of greater
importance than species numbers. When individuals
from other disciplines were asked during lectures and
seminars, particularly conservationists and extension
workers in agriculture and forestry, species numbers
are decisive. In recent years, indices involving even-
ness have essentially fallen out of favour, mostly
because they are difficult to interpret (Gaston, 1996c).
Particularly in agriculture or forestry, single species
are often collected in huge numbers with standardised
methods, which results in a drastic drop of evenness
and hence yields low diversity values, in spite of
comparatively high species richness.
The definition of biodiversity given in the interna-
tional Convention on Biological Diversity (Johnson,
1993) encompasses the genetic diversity within
species, between species, and of ecosystems. Fur-
thermore, Noss (1990) distinguished three sets of
attributes: compositional, structural and functional
biodiversity (see also Fig. 1). The most common ap-
proach is to measure compositional biodiversity. Pre-
sumably, both structural and functional biodiversity
are either based on or lead to higher compositional
P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98 91
diversity. We are convinced that ecosystem diver-
sity, as well as structural and functional diversity, is
somehow reflected in the number of species present.
If they are not correlated with species richness, they
must be special cases and not representative as biodi-
versity indicators. More trophic levels will normally
include more species, and a higher structural diversity
will harbour more ecological niches. In fact, there is
increasing evidence that at least for some taxonomic
groups, species numbers are correlated with habitat
heterogeneity (Moser et al., 2002), but not in others
(Rykken and Capen, 1997).
For all these hierarchical separations or entities
within the huge concept of biodiversity, separate
comprehensible indicators can be researched and de-
veloped. In many cases, however, a rigorous scientific
test may show that the conceptual entities are difficult
to quantify (Prendergast, 1997; Lindenmayer, 1999;
Noss, 1999), or they are basically reflected in other,
Fig. 3. Illustration of the hypothesis that abundant species usually are of higher ecological but lower conservation value, in contrast to
rare and threatened species. Stars indicate red list species collected with pitfall traps, yellow water pans and window interception traps in
a semidry meadow (Duelli and Obrist, 1998). Number of individuals (NInd(log)) are plotted versus number of species (Nspecies).
better quantifiable measures of biodiversity, such
as species richness (Gaston, 1996b; Claridge et al.,
1997).
The aspect of intraspecific diversity is a different
case. To our knowledge there is no published example
of a tested correlation between inter- and intraspecific
diversity.
6. Value systems
People involved in developing or using biodiversity
indicators are influenced by their personal and/or pro-
fessional goals. They all may want to measure or mon-
itor biodiversity, but they address different aspects of
it. Their focus depends on their motivation for deal-
ing with biodiversity. In an agricultural context, and
in an industrialised country in Europe, the three most
important motivations to enhance biodiversity are
92 P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98
1. Species conservation (focus on rare and endangered
species).
2. Ecological resilience (focus on genetic or species
diversity).
3. Biological control of potential pest organisms (fo-
cus on predatory and parasitoid arthropods).
There are additional motivations, of course, but
either they are closely related to the ones mentioned
here, or their causal link to biodiversity is less clear
(e.g. sustainability, landscape protection, cultural
heritage).
Each of these three aspects of biodiversity requires
its own indicators. They often do not correlate with
each other or even show a negative correlation. Con-
sequently, simply adding up different indicators may
lead to misinterpretations, as long as they do not ad-
dress the same aspect of biodiversity. Species con-
servation focusses on rare and threatened species and
often regards more common species in a derogatory
way as ubiquists of little interest. Ecologists, on the
other hand, focus more on abundant species, because a
species on the verge of extinction is likely to have less
significant ecological influence. The hypothesis of an
almost vicarious relationship between the motivations
Fig. 4. Neither red list carabid species nor stenotopic carabid species are correlated significantly with the average number of carabid species
collected in 18 types of habitats using pitfall traps. Data from Foster et al. (1997).
of “species conservation” and “ecological resilience”
is illustrated in Fig. 3.
Prendergast et al. (1993) found low coincidence of
species-rich areas and areas harbouring rare species
for either plants, birds, butterflies or dragonflies. An
investigation of carabid beetles in Scotland (Foster
et al., 1997) showed that neither the number of red
list species nor the number of stenotopic (faunistically
interesting) species are correlated with the mean total
number of carabid species in a variety of habitats such
as moorland, grassland, heathland, peat, saltmarsh,
bracken and swamps (Fig. 4). In an intense investiga-
tion with 51 trap stations and standardised sampling
methods in field and forest habitats in Switzerland,
the number of red list species of all identified arthro-
pod groups was not significantly correlated to overall
species richness per trap station (Fig. 5), while e.g.
the numbers of aculeate Hymenoptera species corre-
lated well (R2=0.88; Fig. 6). In an assessment of
the effects of ecological compensation measures in
Swiss crop fields and grassland, the number of but-
terfly species did not show any correlation with the
species numbers of spiders (Jeanneret, pers. comm.).
In an effort to test the suitability of Collembola as
indicators of the conservation value of Australian
P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98 93
Fig. 5. No significant correlation exists between the number of red list species (from numerous arthropod taxa) and the “overall” number of
arthropods collected with flight traps, pitfall traps and yellow water pans at the same 51 locations (Araneae, Coleoptera, Diplopoda, Diptera
(Syrphidae only), Heteroptera, Hymenoptera (Aculeata only), Isopoda, Mecoptera, Megaloptera, Neuroptera, Raphidioptera, Thysanoptera).
Data from agricultural areas (Duelli and Obrist, 1998) and forest edges (Flückiger, 1999).
grasslands, Greenslade (1997) found no correlation
with species numbers of ants and carabid beetles.
The optimal approach is to select a “basket” of
indicators for each motivation, similar to the Dow
Fig. 6. Species numbers of aculeate Hymenoptera (bees, wasps and ants) show excellent correlation with the overall number of arthropod
species at 51 locations (for details of data sources see Fig. 5).
Jones index for the stock exchange. The measured
indicators within one basket have to be fairly con-
cordant and are pooled to form an index. The re-
sult is a set of three separate indices for the three
94 P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98
basic motivations “conservation”, “ecology” and “pest
control”.
7. How to select indicators for the three main
motivations
7.1. Several steps are necessary
The most accurate indicators of biodiversity are
proven linear correlates of the entity or aspect of biodi-
versity 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 de-
fine 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 third step is a rigorous test for linear cor-
relation in a set of proposed indicators. The urgent
need to perform a scientifically solid test has been ad-
vocated repeatedly (Balmford et al., 1996; McGeoch,
1998; Niemelä, 2000).
Starting with the first step, the three mayor motiva-
tions for protecting or enhancing biodiversity in agri-
cultural landscapes are differentiated.
7.2. Conservation (an index based on the motivation
to protect or enhance threatened species)
For assessing the value of a given habitat, e.g.
an ecological compensation area, for species con-
servation, the entity to indicate is the accumulated
conservation values (e.g. red list status) of all species
present in that area. The highest values are contributed
by species of national or even global importance,
while the so-called ubiquists are of little value. The
second step thus is a comprehensive measurement of
the conservation values in a number of ecosystems or
habitat types.
The third step would be to find and test the best
linear correlate to that otherwise elusive entity “con-
servation value”. The standard indicators for the
conservation basket are numbers of red list species of
selected taxa, weighed according to their category of
threat. However, only very few of the tens of thou-
sands of species present in a country are listed; in
Switzerland they are a mere 7% of all known animal
species (Duelli, 1994). Inevitably, the choice of the
groups of organisms used for an inventory depends
strongly on the red lists available, and on the avail-
ability of specialists to identify the listed organisms.
Lacking the information on the second step (full
account of the conservation value of an area), it is
not currently possible to come up with a scientifically
tested indicator for that value. Nevertheless, a correla-
tion between the cumulated conservation values of all
presently available red listed species per habitat with
the conservation values of single taxonomic groups,
such as birds, butterflies or carabids, would at least
give greater credibility to the red list species approach.
In addition to red list status (degree of threat of ex-
tinction), species values have been calculated on the
bases of national or global rarity (Mossakowski and
Paje, 1985) or endemism. The rationale in the context
of habitat evaluation is that the presence of a nation-
ally or globally rare species increases the biodiversity
value of that habitat, because it contributes more to
the conservation of national or global biodiversity than
the presence of a ubiquitous species.
Only after a reliable basket of indicators for con-
servation value has been established, are further steps
possible to test the correlative power of potential in-
dicators such as length of hedgerows, amount of dead
wood, or the surface of ecological compensation ar-
eas per unit area. Environmental diversity (ED) as a
surrogate measure of the conservation value was pro-
posed by Faith and Walker (1996), but so far there are
no empirical data to test their proposal.
7.3. An index for the motivation “pest control”
For the biodiversity aspect of biological control of
potential pest organisms, the first step may be to de-
fine the measurable entity as the species diversity of
all predators or parasites of potential pest organisms.
For short-term interests, the number of individuals of
beneficial organisms may appear more important than
species richness, because prey and hosts are reduced
by the number of antagonistic individuals rather than
by species numbers (Kromp et al., 1995; Wratten
and Van Emden, 1995). However, with a longer-term
perspective on maintaining a high diversity of antag-
onist species of potential pest organisms is certainly
more important. While the species richness of preda-
tors in a small area can be assessed with reasonable
P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98 95
accuracy and effort, the diversities of parasitoids are
much harder to quantify.
The second step is therefore to test inventory meth-
ods, and selected taxa for their correlation with the
above biodiversity aspect of biological control. At
present species numbers of carabid and staphylinid
beetles, as well as spiders, are often used as indica-
tors because of established standardised collecting
methods (Duffey, 1974; Desender and Pollet, 1988;
Halsall and Wratten, 1988) and readily available keys
for identification and interpretation. Specialised aphi-
dophaga among the syrphid flies, coccinellids and
Neuroptera are another option, but so far the meth-
ods are not fully standardised. Parasitoid wasps and
flies are promising, but so far there is no easy way to
identify them to the species level. Other possibilities
for indicators to test are ratios between herbivores
and predators, or parasitoids and a range of other
arthropods (see e.g. Denys and Tscharntke, 2002).
7.4. An index for ecological resilience
For the basket of indicators for the motivation eco-
logical resilience (“Balance of Nature”, Pimm, 1991),
the entire genetic and taxonomic spectrum of biodi-
versity is the entity to be indicated. The assumption is
that the higher the number of alleles and species, the
higher is the ecological potential of an ecosystem to
react adequately to environmental change.
Here again, a first step requires quantification of
a measurable proportion of local organismic diver-
sity, which can be trusted to represent total species
richness of animals and plants (alpha-diversity). Re-
alistically, only few and small areas will ever be
fully assessed. For the second and third steps, ap-
proximations with large, measurable proportions
of alpha-diversity have to be used to test potential
indicators.
These “ecological” indicators can be seen as indica-
tors for ecosystem functioning (Schläpfer et al., 1999)
and are representing a very basic notion of wholesale
biodiversity. Most studies claiming to measure or in-
dicate biodiversity assume that the group of organisms
they investigate is somehow representative of biodi-
versity. However, in only very few cases has the cor-
relation between a group or several groups of species
with a more or less representative sample of all organ-
isms been measured and published (Abensperg-Traun
et al., 1996; Balmford et al., 1996; Cranston and
Trueman, 1997; Duelli and Obrist, 1998).
8. Effort and costs, the limiting factors for the
choice of measures
8.1. The dilemma of indicating complexity with
simple measures
Large environmental monitoring programmes usu-
ally 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 quan-
tity 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 cor-
relation with aspects of biodiversity. The search for
linear correlates of quantified entities or aspects of
biodiversity is not limited to taxonomic units. Instead
of choosing birds or grasshoppers as indicators, the
spectrum of taxa considered can be determined by an
inventory method such as Berlese soil samples or flight
interception traps. The broader the taxonomic spec-
trum of the samples, the higher the chance of obtain-
ing a good correlation with the entity to be assessed.
Furthermore, indicators, which are not part of the or-
ganismic spectrum, can also be tested in the three-step
approach: habitat diversity and heterogeneity, distur-
bance by traffic, neighbourhood or percentage of pro-
tected areas, etc. At present, various indicators are in
use, but few of them have been tested for their correla-
tion with aspects of biodiversity. At least in Neotropi-
cal butterflies, a positive correlation of species richness
was found with composite environmental indices of
heterogeneity and natural disturbance (Brown, 1997).
8.2. Plots and transects
Plots (for plants) and transects (for birds and in-
sects such as butterflies, dragonflies and grasshoppers)
are widely used relative assessment methods for the
species richness of a selected group of organisms (e.g.
Pollard and Yates, 1993; Wagner et al., 2000). The
main advantages are that the specimens survive the in-
ventory (important for indicating conservation value),
and that large areas can be searched in a relatively
96 P. Duelli, M.K. Obrist/Agriculture, Ecosystems and Environment 98 (2003) 87–98
short time. Scientifically, the drawback is that usually
there are no voucher specimens kept for verifying the
identification. Also, these popular groups (except for
vascular plants) have only few species in agricultural
habitats, so their species richness, even if cumulated,
never reaches 1% of the local species diversity of all
organisms. Their correlation power with local species
diversity has never been tested. Vascular plants, on
the other hand, seem to correlate reasonably well with
overall organismic diversity (Duelli and Obrist, 1998).
Plots and transects are low budget measures and worth
testing for their correlation power in the conservation
and ecology baskets of indicators.
8.3. Standardised trapping methods for arthropods
Pitfall traps for surface dwelling arthropods and var-
ious kinds of flight traps for insects are often used
for biodiversity assessment in agricultural areas. Ei-
ther one or a few taxonomic groups are collected over
longer periods, or a larger number of taxa are sampled
within a shorter collecting period. In both cases, suit-
able correlates have been found for the indicator bas-
ket of ecological resilience (Duelli and Obrist, 1998).
Bugs (Heteroptera), and wild bees and wasps (ac-
uleate Hymenoptera; see also Fig. 6) collected during
an entire vegetation period, where highly correlated
with overall species richness, while carabids and spi-
ders in pitfall traps were not. Reducing the collecting
time to five carefully selected weeks, but extending
the spectrum of identified taxa (Duelli et al., 1999),
yielded correlation values comparable to those of sea-
sonal collections of bugs or bees. Tests are under way
to further reduce the effort required for collecting and
identifying through an adaptation of the Australian
method of Rapid Biodiversity Assessment (Cranston
and Hillman, 1992; Oliver and Beattie, 1996). With
that method, the whole taxonomic spectrum collected
within a few selected weeks in a standardised trap
combination is considered, but only at the level of
morphospecies, i.e. without identifying the catches
to the species level (Duelli et al., unpubl.). Obvi-
ously, the resulting indicator will not be useful for
the indicator baskets of conservation or pest control,
where identification of the species is essential. How-
ever, it is a promising monitoring device for the indi-
cation of alpha-diversity—or the ecological resilience
basket.
9. 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 moti-
vation. 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 sub-
stantial and quantifiable portion of the entity to assess.
The challenge now is to assign all the presently used or
proposed indicators to a basket with a declared value
system—and to test them with empirical measures.
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... Ecological communities are unique, so it is impossible to exactly replace the biodiversity of one area in another, which from a practical sense, would be prohibitively costly and time consuming. As such, surrogates, proxies or indicators are chosen to represent aspects of biodiversity (Bezombes et al., 2018;Duelli & Obrist, 2003;Kiesecker et al., 2009;Macintosh, 2015), particularly where there is a paucity of data available regarding the components, structure and/or function of the affected ecosystem (McElwee, 2017). Indicators are important basis of biodiversity offset markets as they contribute to the 'currency' that can be traded (Benabou, 2014). ...
... In practice, however, this can be difficult to define (Maseyk et al., 2016), as stakeholders can have competing priorities. Each aspect of the ecosystem (or each aspect to be offset) requires a corresponding indicator (Duelli & Obrist, 2003;Quétier & Lavorel, 2011). Indicators should consider threatened and priority species, key species that are very specific to particular habitats, species with restrictive life histories, those that have lost significant habitat due to cumulative effects, and species that are particularly sensitive to human influence (Kiesecker et al., 2009). ...
... different canopy tree species within the same vegetation type, or genes 132 within species) (Maseyk et al., 2016). In order to avoid concealed trades, rigorous science must be applied to ensure that all natural values are known and that appropriate indicators for each natural value are included (Duelli & Obrist, 2003). ...
Thesis
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Biodiversity offsets, also called “environmental offsets”, are actions used to compensate for the loss of biodiversity and social values associated with development projects. They are commonly used by governments to contribute to ecologically sustainable development (ESD); however, offsets have been criticised for inappropriate use, poor implementation, and inadequate monitoring, reporting and enforcement. Regardless, use of offsets is likely to increase due to regulatory convenience in easing community discomfort with development impacts. This thesis investigated how biodiversity offsets in Australia can be enhanced to align with ESD principles. Analyses of peer-reviewed journal articles, published reports, media articles and legislative instruments for biodiversity offsets across Australian jurisdictions was used to determine requirements, similarities, equity, effectiveness and transparency in application. These analyses were then used to develop a model for biodiversity offsets that balances the three key aspects of ESD (environmental, social, economic). A comparison of policy and legislation in Australian jurisdictions found inconsistency and gaps in equity, transparency, measurability and effectiveness. Furthermore, Australian Commonwealth offset requirements were not improved (mature) after implementation of a biodiversity offset policy in October 2012. These learnings and further review were used to identify that cost and risk considerations, and use of strategic planning frameworks, bonds and advanced offsets, were key to improving offset use for ESD. Inclusion of conservation trust funds to deliver biodiversity offsets aligned with ESD principles, made the offsets model developed in this thesis suitable in areas with a paucity of available land. Finally, assignment of responsibilities, coupled with interchangeability of roles and a focus on collaboration, was found to be important for ensuring offsets are efficient, ethical, robust and strategic. While this research has been developed in an Australian context, the findings have broader applicability globally, with the ability to address nature positive requirements and international commitments to protect biodiversity and minimise climate change.
... Biodiversity measurement practices include the identification of biodiversity indicators, the formulation of indices, and the development of tools and instruments for data collection and analysis. Biodiversity indicators pick aspects of a complex object of measurement qualitatively, facilitating quantification (Duelli and Obrist 2003;Pereira et al. 2013;Rochette et al. 2019). There are no overall best indicators of biodiversity because they are "expressive of particular sets of concerns" (Williamson and Leonelli 2022, p. 178). ...
... various types of diversity, and biological control science (of which crop science is a branch), which tackles the impact of pests (Duelli and Obrist 2003). Each field identifies and studies specific aspects of diversity. ...
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This paper challenges “biodiversity skepticism:” an inferential move that acknowledges the proliferation, heterogeneity, and lack of covariance of biodiversity measurements, and concludes that we should doubt the scientific validity of the biodiversity concept. As a way out of skepticism, philosophers have advocated for eliminating “biodiversity” from scientific inquiry, revising it, or deflating its meaning into a single measurable dimension. I present a counterargument to the inferential move of the skeptic by revealing how it stands on two unstated premises, namely a reflective view of measurements and the unidirectional dynamics between definitional and measurement practices, and corollary assumptions. These premises and assumptions are misaligned with a richer theoretical understanding of measurement and are sometimes inconsistent with how science operates. A more nuanced view of measurement could better explain measurement proliferation while being consistent with new ways in which the general biodiversity concept could be useful. To conclude, I urge philosophers of measurement and conceptual engineers to collaborate in tackling the interplay between conceptual change and measurement practices.
... Such data is needed to raise awareness, inform policymakers, better understand ecological systems, and plan and evaluate management actions (Jones et al. 2011). Its high complexity makes biodiversity difficult to measure (Duelli and Obrist 2003) and poses a challenge for communication towards stakeholders and the public. Therefore, multiple indicators were developed to assess different aspects of biodiversity and to summarise results in easily understandable metrics. ...
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Aim The integration of high‐quality field data with high‐resolution remote sensing data can give detailed insights into the spatial distribution of biodiversity and provide valuable information for biodiversity conservation at a scale relevant for management action. We developed a framework based on remote sensing data and field surveys for modelling species richness and abundance of butterflies at high spatial resolution to inform about the spatial distribution of butterfly species richness and abundance and analyse their drivers and the scale of effect of landscape factors. Location Western Austria. Methods We combined structured butterfly surveys at 175 grassland sites in western Austria with remote sensing variables describing topography, grassland characteristics, and the landscape composition and configuration at different radii around a site. For spatial predictions of butterfly species richness and abundance, generalised linear models with elastic net regularisation were used and compared with stepwise variable selection. To analyse the influence of selected variables and their scale of effect, models with landscape variables in different radii around the sites and variables describing topography were applied. Results For species richness, the Spearman rank correlation between predicted and measured values was 0.62. For abundance, predictive power was lower with a correlation of 0.52. Models with variables from smaller radii (125 and 250 m) generally showed better predictive performance than those at larger radii (500 and 1000 m). We found an effect of elevation, maximum grassland productivity, northness, and forest ecotone density in most models. Main Conclusions Integrating remote sensing data with spatial modelling techniques substantially enhances our ability to understand patterns and identify key drivers of butterfly species richness at high spatial resolution. Our study highlights the positive influence of forest edges, small woody features, and moderate grassland productivity on butterfly species richness and abundance.
... However, while from a technical perspective, future weeding robots might be able to increase the detectability of biodiversity, the effect on scheme efficiency strongly depends on the actual biodiversity indicators chosen, which in turn depends on the scheme's goal, such as conservation of rare species vs. ecological resilience vs. biological pest control (Duelli and Obrist, 2003). ...
Article
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Payments for ecosystem services (PES) are commonly used to reduce negative impacts on biodiversity by intensive agricultural production. Whether action-or results-based, the efficiency of PES schemes in terms of conservation benefit per costs, hinges on cost-effective monitoring, actions farmers are rewarded for, appropriate biodiversity indicators and, farmers' acceptance. Despite expectations that novel technologies, such as weeding robots, will reduce monitoring costs, the potential impact of their widespread use on optimal PES design for biodiversity conservation in arable farming remains unexplored. Our study investigates 1) the influence of weeding robots on optimal scheme design and 2) the challenges and options that arise for future PES scheme design. To this end, we use a simulation model to systematically compare how the availability of weeding robots changes the preferability of action-based versus results-based payments under various production and management conditions. This study sheds light on the transformative potential of weeding robots in optimising PES for biodiversity conservation. The results indicate that the difference in efficiency between action-and results-based schemes vanishes if robots can perform biodiversity-sensitive actions. Further, we find that it is even more important for the future design of PES to be able to define multidimensional biodiversity goals-a major challenge calling for interdisciplinary research.
... Climate change (CC) significantly affects global and national development programs [1,2]. Sadly, CC affects farming more than any other enterprise worldwide [3,4]. The shocks and impacts of CC on soil degradation are predicted to be more harmful than good because they compromise farming systems, cause drastic reduction of individual farmer ...
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Understanding and appreciating climate solutions for soil management in smallholder farmlands are paramount. These climate solutions inform smallholder farmers' actions, choices, decisions and priorities to tackle specific climate change problems and opportunities. The study used structured and semi structured questionnaires to collect field data to ascertain smallholder farmers' knowledge about vegetation based climate solutions for soil management in Kabale and Rubanda districts, Uganda. A purposive sampling technique was used to collect data from 367 smallholder farmer household head respondents. Regression model, specifically linear to test multicollinearity and multinomial logistic and descriptive statistics was utilised to examine vegetation based climate solutions for soil management. Vegetation based climate solutions such as crop residues, selected trees, Napier grass and Seteria grass (dependent) and gender, age and marital status, and level of education information (independent) were determined predictor variables. The findings revealed that both genders, males (51.5%) and females (48.5%), witnessed climate change as demonstrated in Fig. 2. The chi-square test (χ 2 = 376.337) indicated a significant difference between smallholder farmers' implementing climate solutions. The study observed positive Kendall's tau (0.357 and 0.118) and a p-value (0.002 and 0.289) of temperature and rainfall respectively. Most farmers (69.2%) relied on fellow farmers as a major source of climate information to manage soil and enhance soil fertility. Vegetation based climate solutions 33.8%, (planting Napier grass, selected tree species, and crop residues) were revealed as suitable and effective soil management interventions to control soil erosion and fertility improvement in smallholder farmlands. Climate solutions were significantly influenced by level of education (0.000) and farmland size (0.001) at 0.05. Therefore, there is a need to incorporate vegetation based climate solutions into government development programmes and agendas to enhance soil fertility and erosion management in smallholder farmers' farmlands with a focus on livelihood improvement through increasing crop yields and hunger alleviation.
... As the fundamental building block of biodiversity, genetic diversity forms the cogs and wheels that comprise a population's adaptive potential. However, identifying and quantifying biodiversity at each hierarchical level of diversity-including genes, species, and ecosystems-is a complex undertaking, with distinct frameworks to enumerate compositional, structural, and functional diversity (Petchey and Gaston 2002;Duelli and Obrist 2003;Péru and Dolédec 2010). Functional genetic diversity includes sequence polymorphisms and differences in gene expression, which together shape the phenotypic diversity that comprises differences in morphology, physiology, and life-history characteristics present within a population. ...
Article
Genetic diversity is the fundamental building block of biodiversity and the necessary ingredient for adaptation. Specifically, the intra-specific diversity (biocomplexity) comprised of phenotypic and genetic variation partitioned within and among populations can determine the ability of a species to respond to changing environmental conditions. Here, we explore the biocomplexity of California’s Central Valley Chinook salmon (Oncorhynchus tshawytscha) population complex at the genomic level by quantifying population genomic diversity among and within migration life-history phenotypes. Notably, despite apparent gene flow among populations with the same migration (life history) phenotypes inhabiting different tributaries, each group is characterized by a distinct component of unique genomic diversity. While enumerating biodiversity contained within individual hierarchical levels is informative, it is important to consider inter- and intra-specific diversity simultaneously as there may be emergent properties at higher levels due to presence of diversity at lower ones. Our results emphasize the importance of formulating conservation goals focused to maintain biocomplexity at both the phenotypic and genotypic level. Doing so will preserve the species’ adaptive potential and increase the probability of persistence of the population complex despite changing environmental pressures.
... Species richness is a frequently used metric for measuring biodiversity in urban green spaces (Matthies et al., 2017). While there are limitations to using species richness as an indicator of biodiversity -such as not providing information on the abundance of species or the types of species present on site (Duelli and Obrist 2003) -species richness was considered a useful metric as it did not rely on complete survey count data to the same extent as other biodiversity metrics (Magurran 2021). For this reason, species richness is particularly useful when dealing with crowdsourced data that is characterised by semi-structured presence-absence data (Johnston et al., 2022). ...
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Cities are crucial for supporting biodiversity and are likely to play an important role in helping respond to the global biodiversity crisis. Understanding how plants and animals utilize various urban spaces is essential for designing cities that accommodate both human and ecological needs. Informal green spaces (IGS) have been historically overlooked in green space research and planning. However, there is growing interest in the potential benefit of IGS in supporting urban biodiversity. This study builds on previous research by examining the contribution of IGS to biodiversity at the metropolitan scale. We do this by mapping IGS across the entire urban landscape of Greater Melbourne, Australia, using crowdsourced ecological survey data to assess the role of IGS in supporting native bird and plant species richness. Our findings indicate that IGS contribute to urban species richness and can do so to a similar extent as formal green spaces. We found that utility easements and brownfield sites were particularly important types of IGS for supporting species richness. While formal green spaces like parks remain vital for urban biodiversity, IGS should be considered an integral part of urban greenspace networks. These findings underscore the need to more actively consider IGS in urban green space decision making in order to achieve positive urban biodiversity outcomes.
... Defining the specific biodiversity goal of a land management strategy is critical to the success of a project (Duelli & Obrist, 2003). ...
Article
Simplification of agricultural environments is linked to declines in biodiversity. Improving the floral diversity within and around these areas may result in more robust and diverse ecosystems. We investigated how floral resource abundance, diversity, and species composition in a cranberry agricultural system correlated to the abundance and overall invertebrate diversity and to the abundance and diversity of specific invertebrate groups of agricultural importance (e.g. parasitoids, phytophagous taxa, pollinators and predators). This study focused on habitats immediately surrounding cranberry production and included grassy dikes under a managed system (‘dike’), and semi‐natural areas growing on the surrounding support land (‘semi‐natural’). Floral resource availability and diversity tended to be similar between habitats, while invertebrate richness, diversity and composition differed. As the availability of floral resources increased, invertebrate abundance increased but diversity decreased. Overall invertebrate community composition differed with the specific species and availability of floral resources. The habitat type and floral resource composition impacted some agriculturally important groups, as pollinator abundance was higher in the semi‐natural habitat, and parasitoid abundance varied with floral resource composition across both habitats. These results suggest that managing the structural and floral resource diversity associated with agroecosystems can help support local biodiversity. However, these systems may disproportionately benefit more common taxonomic groups. The difference in responses of individual taxonomic groups also highlights the potential tradeoffs of focusing on only a subset of biodiversity aspects.
... The choice of indicators depends on the aspect or entity of biodiversity to be evaluated and is guided by a specific value system based on particular motivation/s. Each biodiversity index (BI) for a system should consist of a group of methods with one or several consistent indicators (Duelli & Obrist, 2003). ...
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For monitoring responses of insect arthropods to disturbance, a dataset of 1831 insects was considered. We studied faunal diversity of insects in terraces habitats located on the coast of Lebanon. Insects were sampled from 12 sites having different habitats with one sampling method of combined pitfall-pan trap. This study resulted in nine insect orders and 129 morphospecies. Hymenoptera was the most abundant order in all habitats (63.57%) followed by the orders Diptera, Homoptera, Coleoptera, Orthoptera, Hemiptera, Lepidoptera, Dictyoptera and Thysanoptera. This coast was classified with medium biodiversity index (D) of 0.51 for insect orders and high D of 0.83 for morphospecies. The highest (D) was in field crops habitat (H1) of 0.64 and 0.91 for insect orders and morphospecies, respectively; followed by scrublands (H3), greenhouse areas (H2) and olive orchards (H4). These results indicated that human intervention was affecting the diversity in natural habitats. Five insect orders: Coleoptera, Dictyoptera, Diptera, Hymenoptera, and Lepidoptera were significantly selected as potential biodiversity indicators in this coastal area. Thus, for monitoring these bioindicators, a protocol based on operating our combined trap method appears practical in design and yield very diverse material with the target of sustaining these insect populations in the coastal area.
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Large saaie sampling was performed by means of different techniques during several annual cycles in a pasture ecosystem. Collector curve- and precision-analyses show that an evaluation of carabid species richness, based on pitfall data only, inherently carries with it a number of risks. The effect of increased sampling effort is evaluated through precision estimates by two different approaches. Decisions on the necessary number of sampling units for a desired precision, however, largely follow from statistical considerations only.
Article
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Twenty two predominantly native grassland sites of varying levels of disturbance and community type were sampled for Collembola using a suction sampler in spring. Specimens were identified to species and composition and abundance of the collembolan fauna at each site compared using a number of methods. Different analyses did not produce a similar ranked order for the sites except that the most pristine site, of highest conservation value, always ranked highly and the three most weed infested disturbed sites were always at the bottom of the rankings. The ranking method which conformed most closely to ranked weediness values was that based simply on species richness and species abundance of both exotic and native species considered separately. No congruence was found between rankings of sites based on species richness of ants, carabid beetles and Collembola indicating that cautions should be applied when using surrogate taxa. The cluster analysis indicated that grassland type was the most important factor determining the composition and abundance of collembolan faunas. It is concluded that the intrinsic variation in these ecological systems is too great for a linear response to disturbance to be shown by the invertebrates studied here which makes it unlikely that a single, reliable indicator can be found.
Article
The United Nations Conference on the Environment and Development brought over 100 governments together in Rio de Janeiro (3-14 June 1992) to agree action and legal bases for the future protection of the environment. This text elucidates the UNCED process and the Conference itself by assembling the key documents, including the final version of Agenda 21, and using them to recount how UNCED began, developed and finally, in Rio, came to fruition. Each document is preceded by analytical commentary, and a comprehensive index has been included.