Indicator Assessment

Abundance and distribution of selected species

Indicator Assessment
Prod-ID: IND-140-en
  Also known as: SEBI 001 , CSI 050
Published 08 Aug 2016 Last modified 11 May 2021
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Since 1990, common bird populations have decreased by around 15 % in Europe (27 European countries). The decline of common farmland birds was more pronounced at 34 % in all countries with monitoring schemes - and 31 % in EU Member States - whereas common forest bird populations declined by 12 % over the same period.

Grassland butterflies have shown a significant rate of decline of 30 % between 1990 and 2013 in Europe (21 European countries). In the last 10 years, the rate of loss is slowing down.

Population index: Common Birds in Europe

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European grassland butterfly

Grassland butterflies in Europe
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Grassland butterflies in EU
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Despite a slow levelling off of the downward trend, populations of all common birds in Europe - including common farmland and forest species (Fig. 1) - have declined since 1990. While the indicator takes 1990 as a starting point, it should be borne in mind, however, that significant losses had already happened before this date.

In spite of year-to-year fluctuations, grassland butterfly numbers are declining severely; their populations have decreased by 30 % since 1990, although in the last 10 years there have been some signs of levelling off (Fig. 2). Similarly to birds, the dramatic reductions since 1990 certainly add to population losses before that time, although no structured data series are available. 


Birds and butterflies are sensitive to environmental change and can reflect changes in ecosystems as well as in other animals and plants. Trends of their populations can thus be excellent barometers of the health of the environment.   

The long-term trends for common farmland and forest birds as well as grassland butterflies demonstrate that Europe has experienced a major decline in biodiversity associated with agro-ecosystems and grasslands. This was primarily due to habitat change – including loss, fragmentation and degradation – of natural and semi-natural ecosystems. The change was mainly caused by homogenisation and loss of habitat as a result of agricultural intensification, intensive forest management, land abandonment and urban sprawl.


The challenge now is to deploy widely the conservation measures of European policies (such as Birds and Habitats Directives and the Water Framework Directive) as well as the environmental measures within the Common Agricultural Policy (CAP) in order to help populations recover at national and European scales.


An increase in the population index means that there are more species with increased populations than those with decreased populations: it does not necessarily mean that the population of all species has increased. This situation may be due to an expansion of some species (typically, generalists) at the expense of other species (typically, specialists). It must also be noted that populations fluctuate on a yearly basis.

In the absence of information on abundance, information on the distribution of species can help assess species status. However, at European level, this type of information is still weak for other groups of species.


Supporting information

Indicator definition

This indicator shows trends in the abundance of common birds and butterflies over time across their European ranges.



Index (relative values, 1990 set to 100)


Policy context and targets

Context description

a. common birds

The EU has taken action on the protection of biodiversity for a considerable number of years, for example, by adopting the Birds Directive 0409/1979 and the Habitats Directive 0043/1992. In 2001, the Gothenburg European Council adopted the sixth Environmental Action Programme of the EU, which included the objective of halting biodiversity loss by 2010. In response to its commitments under the Convention of Biological Diversity, the EU also adopted the Biodiversity Action Plan for Agriculture in 2001.

The Message from Malahide was adopted in May 2004 at the stakeholders' conference on Biodiversity and the EU - Sustaining Life, Sustaining Livelihoods, jointly organised by the Irish Presidency and the European Commission in Malahide. The Message identified 18 objectives and related targets that could form the basis for future priority action in reaching the 2010 EU target of halting the loss of biodiversity (the Gothenburg objective) as well as contributing to the global target of significantly reducing the current rate of loss of biodiversity by 2010.

In line with the results of The Tenth meeting of the Conference of the Parties to the Convention on Biological Diversity (CBD), held in Nagoya, Japan (October 2010), a new EU biodiversity strategy Our life insurance, our natural capital: an EU biodiversity strategy to 2020 was adopted by the European Commission in May 2011. This provided a framework for the EU to meet its own biodiversity objectives and global commitments as a party to the CBD. The strategy is built around six mutually supportive targets, which address the main drivers of biodiversity loss and aim to reduce the key pressures on nature and ecosystem services in the EU. Each target is further translated into a set of time-bound actions and other accompanying measures. The strategy also highlights the need to enhance contributions from other environmental policies and initiatives including sectoral integration across EU policies such as agriculture, fisheries, forestry, water, climate and energy. Target 3A of the strategy seeks to maximise “areas under agriculture across grasslands, arable land and permanent crops that are covered by biodiversity-related measures under the Common agricultural policy (CAP) so as to ensure the status of species and habitats that depend on, or are affected by agriculture”.

Moreover, this indicator needs to be seen in the context of the CAP, in particular its rural development part and the proposals for CAP reform post-2013. Relevant policy measures under the rural development policy include agri-environmental schemes and compensatory allowances for areas of natural constraint, including areas with environmental restrictions.

b. butterflies

Insects are by far the most species-rich group of animals, representing over 50% of terrestrial biodiversity. Contrary to most other groups of insects, butterflies are well documented, easy to recognise and popular with the general public. Butterflies use the landscape at a fine scale and react quickly to changes in management, intensification or abandonment. Furthermore, a sustainable butterfly population relies on a network of breeding habitats scattered over the landscape, where species exist in a metapopulation structure. This makes butterflies especially vulnerable to habitat fragmentation. Moreover, many butterflies are highly sensitive to climate change and nitrogen deposition and, because data from fine-scale mapping is available in many countries, they have been used in models predicting the impact of climate change on wildlife. Butterflies have been counted in Butterfly Monitoring Schemes since 1976.

Relation of the indicator to the focal area

a. common birds

Each species reacts differently to the various anthropogenic pressures that potentially
impact on the population size. By monitoring a large enough number of populations
from different bird groups, different bio-geographical regions and areas subjected to
different types and levels of pressures, this indicator has the potential to alert decision
makers to the decline of populations in relation to environmental and geographic
factors, as well as their potential drivers.

b. butterflies

The European Butterfly Indicator will be able to deliver a reliable measurement of
changes in the size of European butterfly populations. Since butterfly trends are a good
indicator of changes in the insect group as a whole, which in turn represents more than
50% of Europe's biodiversity, the European Butterfly Indicator is a useful proxy for a
wider understanding of biodiversity changes.


EU 2020 Biodiversity Headline Target

Related policy documents

  • EU 2020 Biodiversity Strategy
    in the Communication: Our life insurance, our natural capital: an EU biodiversity strategy to 2020 (COM(2011) 244) the European Commission has adopted a new strategy to halt the loss of biodiversity and ecosystem services in the EU by 2020. There are six main targets, and 20 actions to help Europe reach its goal. The six targets cover: - Full implementation of EU nature legislation to protect biodiversity - Better protection for ecosystems, and more use of green infrastructure - More sustainable agriculture and forestry - Better management of fish stocks - Tighter controls on invasive alien species - A bigger EU contribution to averting global biodiversity loss


Methodology for indicator calculation

a. common birds

Trend information is derived from annual national breeding bird surveys in 27 European countries and spanning different periods. These surveys are obtained through the Pan-European Common Bird Monitoring scheme (PECBM) (1). A software package named TRIM (Trends and Indices for Monitoring data) is used to calculate national species' indices and then to combine these into supranational indices for species, weighted by estimates of national population sizes. TRIM allows for missing counts in the time series and yields unbiased yearly indices and standard errors using Poisson regression. Weighting is applied to allow for the fact that different countries hold different proportions of each species' European population. Updated population size estimates, derived from BirdLife International , are used for weighting. Although national schemes differ in count methods in the field, these differences do not influence the supranational results because the indices are standardised before being combined. An improved hierarchical imputation procedure was introduced in 2005 to calculate supranational indices. Supranational indices for species were then combined on a geometric scale to create multi-species indicators. For more details see Gregory et al. 2005.

List of species

Common farmland birds, Europe:
Alauda arvensis, Burhinus oedicnemus, Carduelis carduelis, Columba palumbus, Emberiza citrinella, Falco tinnunculus, Galerida cristata, Hirundo rustica, Lanius collurio, Lanius senator, Limosa limosa, Miliaria calandra, Motacilla flava, Passer montanus, Saxicola rubetra, Streptopelia turtur, Sturnus vulgaris, Sylvia communis, Vanellus vanellus.

Common forest birds, Europe:
Anthus trivialis, Bonasa bonasia, Carduelis flammea, Carduelis spinus, Certhia rachydactyla,
Certhia familiaris, Coccothraustes coccothraustes, Dendrocopos minor, Dryocopus martius, Ficedula albicollis, Ficedula hypoleuca, Fringilla montifringilla, Garrulus glandarius, Hippolais icterina, Jynx torquilla, Lullula arborea, Luscinia megarhynchos, Muscicapa striata, Oriolus oriolus, Parus ater, Parus caeruleus, Parus montanus, Parus palustris, Phoenicurus phoenicurus, Phylloscopus collybita, Phylloscopus sibilatrix, Picus canus, Picus viridis, Prunella modularis, Pyrrhula pyrrhula, Regulus regulus, Sitta europaea, Sylvia borin.

Other common birds, Europe:
Accipiter nisus, Aegithalos caudatus, Buteo buteo, Carduelis cannabina, Carduelis chloris, Cettia cetti, Cisticola juncidis, Corvus corone corone/cornix, Corvus monedula, Cuculus canorus, Dendrocopos major, Emberiza schoeniclus, Erithacus rubecula, Fringilla coelebs, Motacilla alba, Parus major, Phylloscopus trochilus, Pica pica, Sylvia atricapilla, Sylvia melanocephala, Troglodytes troglodytes, Turdus merula, Turdus philomelos, Turdus viscivorus, Upupa epops.

Rationale for species selection:

The species selection for the indicator produced in June 2005 was based on BirdLife's Habitats for birds in Europe (Tucker and Evans 1997) - arguably the most comprehensive treatment of habitats and habitat use by birds. It quantitatively assesses the proportion of each species' population that occurs in predefined habitat types across Europe. The overall assessment, while mostly quantitative, also relied to some degree on expert judgment through habitat working groups.

In the PECBM scheme, species were classified according to habitat using the assessment of Tucker and Evans (1997), with the exception that montane grassland (originally included as a sub-class of agricultural habitats) was classified as a separate habitat. All species with more than 75% of their population occurring in one of the following eight habitats were classified as specialists of that habitat: marine; coastal; inland wetland; tundra, mires and moorland; boreal and temperate forests; Mediterranean forest, shrubland and rocky habitats; agricultural and grassland (excluding montane grassland); and montane grassland (Tucker and Evans 1997).

In addition, species with 10-75% of their population using only one of the above habitats were classed as specialists in that habitat, according to either Tucker and Evans (1997) for Species of European Conservation Concern (SPECs), or Snow and Perrins (1998) for non-SPECs. Species with 10-75% of their population in three or more woodland or farmland sub-categories in Tucker and Evans (1997) and 10-75 % of their population in only one other habitat category were classified as woodland or farmland specialist species respectively.

Remaining species with more than 10% of their population occurring in more than one habitat were classed as non-specialists. Any species that did not meet the above criteria (due to insufficient data) remained unclassified. Tucker and Evans (1997) include a further habitat - lowland Atlantic heathland, however, no species met the criteria to be classed as a specialist of this habitat.

This species-habitat classification is being used in a number of BirdLife analyses, for example, an analysis of farmland birds and long-distance migrants using Birds in Europe 2 trends (Donald et al., 2006; Sanderson et al., 2006). The PECBM scheme also explores a bio-geographical approach to species selection and habitat choice knowing that some species may have different habitat preferences according to the bio-geographical context.

b. butterflies

The field method is based on the British Butterfly Monitoring Scheme (Pollard and Yates, 1993), in use in the United Kingdom since 1976. Counts are made on a line transect of 5 or 10m wide with homogeneous vegetation and vegetation structure. From March or April to September or October all butterflies 2.5m to the left and right of the recorder and 5m in front and above should be counted under standardised weather conditions. The frequency varies from weekly to three or four visits during the season. Most of the sites are recorded by skilled volunteers. All recorders have a good knowledge of the butterfly fauna at their transect, and their results are checked by butterfly experts. Feest (2006), and van Swaay and Feest (in prep.) show that butterfly survey data can be used to generate biodiversity quality indices for sites such that trends in biodiversity quality can be deduced. This will provide evidence of change more quickly than simple assessments and in a stastically robust way.

The main objective of the monitoring schemes is to assess changes in abundance at national and regional levels of butterflies, including species of the Habitat Directive.

A European index and trend is produced for each species by combining national results for that species. The individual European species indices are combined (averaged) to create multi-species supranational indicators. This method is based on the one for bird indicators (Gregory et al., 2005):

1. At National level: the indices for each species are produced for each country, using TRIM (Pannekoek and Van Strien, 2003). TRIM is a computer programme to analyse time-series of counts with missing observations using Poisson regression.

2. At Supranational level: to generate European trends, the difference in national population size of each species in each country has to be taken into account. This weighting allows for the fact that different countries hold different proportions of a species' European population (Van Strien et al., 2001). A weighting factor is established as the proportion of the country (or region) in the European distribution (Van Swaay and Warren, 1999). The missing year totals are estimated by TRIM in a way equivalent to imputing missing counts for particular sites within countries (Van Strien et al., 2001).

3. At multi-species level: for each year the geometric mean of the supranational indices is calculated.

List of species

Widespread species: Ochlodes sylvanus, Anthocharis cardamines, Lycaena phlaeas, Polyommatus icarus, Lasiommata megera, Coenonympha pamphilus and Maniola jurtina.

Specialist species: Erynnis tages, Thymelicus acteon, Spialia sertorius, Cupido minimus, Phengaris arion, Phengaris nausithous, Polyommatus bellargus, Cyaniris semiargus, Polyommatus coridon and Euphydryas aurinia.

(1) The PECBM scheme is a partnership involving the European Bird Census Council, the Royal Society for the Protection of Birds, BirdLife International and Statistics Netherlands that aims to deliver policy relevant biodiversity indicators for Europe.

Methodology for gap filling

TRIM (TRends and Indices for Monitoring data) is a software package used to determine species' population trends. It allows for missing counts using estimation, and yields yearly indices and standard errors using Poisson regression. The latest version can be downloaded from the web site of Statistics Netherlands.

Methodology references

  • a. common birds BirdLife International (2004). Birds in Europe: population estimates, trends and conservation status. Cambridge, United Kingdom: BirdLife International (BirdLife Conservation Series No. 12). Donald, P. F., Sanderson, F. J., Burfield, I. J., van Bommel, F. P. J. (2006). Further evidence of continent-wide impacts of agricultural intensification on European farmland birds, 1990-2000. Agriculture, Ecosystems and Environment 116 (2006) 189-196. Gregory, R. D., van Strien, A., Vorisek, P., Meyling, A. W. G., Noble, D. G., Foppen, R. P. B. and Gibbons, D. W. (2005) Developing indicators for European birds. Phil.Trans. R. Soc. B. 360, 269-288. Sanderson, F. J., Donald, P. F., Paina, D. J., Burfield, I. J., van Bommel, F. P. J. (2006). Long-term population declines in Afro-Palearctic migrant birds. Biological Conservation 131 (2006) 93-105. Snow, D. W., Perrins, C. M., (1998). The Birds of the Western Palearctic: Concise Edition. Oxford University Press, Oxford, United Kingdom. Strategy for the Wider Environment. BirdLife International, Cambridge, United Kingdom. Tucker, G. M., Evans, M. I., (1997). Habitats for Birds in Europe: A Conservation.
  • b. butterflies Donald, P. F.; Sanderson, F. J.; Burfield, I. J.; Bierman, S. M.; Gregory, R. D.; and Waliczky, Z., 2007. 'International Conservation Policy Delivers Benefits for Birds in Europe'. Science 317: 810 Feest, A. (2006) Establishing baseline indices for the environmental quality of the biodiversity of restored habitats using a standardised sampling process. Restoration Ecology, 14:112-122. Gregory, R. D., Van Strien, A. J., Vorisek, P., Gmelig Meyling, A. W., Noble, D. G., Foppen, R. P. B. and Gibbons, D. W. (2005) Developing indicators for European birds. Phil. Trans. R. Soc. B. 360, 269-288. Pannekoek, J. and Van Strien, A. J. (2003) TRIM 3 manual. Trends and Indices for Monitoring data. CBS, Statistics Netherlands, Voorburg, Netherlands. Pollard, E. and Yates, T. J. (1995) Monitoring butterflies for ecology and conservation. Chapman and Hall, Londen. Thomas, J. A., Telfer, M. G., Roy, D. B., Preston, C. D., Greenwood, J. J. D., Asher, J., Fox, R., Clarke, R. T. and Lawton, J. H. (2004) Comparitive losses of British Butterflies, Birds, and Plants and the Global Extinction Crisis. Science 303, 1879-1881. Thomas, J. A. (2005) Monitoring change in the abundance and distribution of insects using butterflies and other indicator groups. Phil. Trans. Soc. B. 360, 339-357. Van Strien, A. J., Pannekoek, J. and Gibbons, D. W. (2001) Indexing European bird population trends using results of national monitoring schemes: a trial of a new method. Bird Study 48, 200-213. Van Swaay, C. A. M. and Warren, M. S. (1999) Red Data Book of European Butterflies (Rhopalocera). Nature and Environment series, No. 99, Council of Europe, Strasbourg. Van Swaay, C. A. M., Nowicki, P., Settele, J., van Strien, A.J. (2008) Butterfly monitoring in Europe: methods, applications and perspectives, Biodivers Conserv DOI 10.1007/s10531-008-9491-4 Van Swaay, C. A. M., van Strien, A.J. (2005) Using butterfly monitoring data to develop a European grassland butterfly indicator. In Proceeding Studies on the ecology and conservation of Butterfliesin Europe, december 2005
  • The European Butterfly Indicator for Grassland species 1990-2013 Van Swaay, C.A.M., Van Strien, A.J., Aghababyan, K., Åström, S., Botham, M., Brereton, T., Chambers, P., Collins, S., Domènech Ferrés, M., Escobés, R., Feldmann, R., Fernández-García, J.M., Fontaine, B., Goloshchapova, S., Gracianteparaluceta, A., Harpke, A., Heliölä, J., Khanamirian, G., Julliard, R., Kühn, E., Lang, A., Leopold, P., Loos, J., Maes, D., Mestdagh, X., Monasterio, Y., Munguira, M.L., Murray, T., Musche, M., Õunap, E., Pettersson, L.B., Popoff, S., Prokofev, I., Roth, T., Roy, D., Settele, J., Stefanescu, C., Švitra, G., Teixeira, S.M., Tiitsaar, A., Verovnik, R., Warren, M.S. (2015). The European Butterfly Indicator for Grassland species 1990-2013. Report VS2015.009, De Vlinderstichting, Wageningen


Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

No uncertainty has been specified

Rationale uncertainty


a. common birds

  • Temporal coverage: until the early 1990s, rather few European countries had common bird monitoring schemes in place, which restricts how far back in time representative trends can be calculated.
  • Spatial coverage: coverage of western and central Europe is now almost complete, but a few gaps remain, and a further expansion eastwards is desired; efforts to fill them are underway.

b. butterflies

  • Limited geographical coverage.


As another candidate indicator for the headline indicator, the living planet index (LPI) was considered. The weakness of the LPI is that it relies on data that is biased towards well-monitored vertebrates in temperate latitudes, including many species that have been/are subject to ongoing conservation action, and thus is not representative of biodiversity as a whole. It relies on a limited amount of reliable time-series data gathered from a variety of sources published in scientific journals, NGO literature, or on the worldwide web. Work is ongoing to strengthen the LPI.

The PECBM indicator work is based on generic sampling of species, with no a priori bias on their selection. It has been presented and well-received at international conferences and meetings.

Options for other biodiversity species-based indicators are being considered.

Data sources

Other info

DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • SEBI 001
  • CSI 050
Frequency of updates
Updates are scheduled once per year
EEA Contact Info


Geographic coverage

Temporal coverage