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Indicator Assessment
Long-term monitoring schemes show significant downward trends in common farmland birds and in grassland butterfly population numbers, with no signs of recovery.
Between 1990 and 2017, there was an 8 % decline in the index of 168 common bird species in the 25 EU Member States with bird population monitoring schemes and the United Kingdom (UK). The common forest bird index showed no decrease over the same period. The decreases were slightly greater if figures for Norway and Switzerland are included: 11 % for all common birds and 2 % for forest birds.
The decline in common farmland bird numbers between 1990 and 2017 was much more pronounced, at 33 % (EU Member States and UK) and 35 % (if Norway and Switzerland are included).
The index of grassland butterflies has declined strongly in the 15 EU countries where butterfly monitoring schemes exist. In 2017, the index was 39 % below its 1990 value.
Birds and butterflies are sensitive to environmental change and their population numbers can reflect changes in ecosystems as well as in other animal and plant populations. Trends in bird and butterfly populations can, therefore, be excellent barometers of the health of the environment. The status of birds and butterflies has been the subject of long-term monitoring in Europe, much of it via voluntary effort. Both species groups have a strong resonance with the interested public and are good examples of how the power of citizen science can be released through effective targeting.
The long term trends (over 25 years) revealed by monitoring schemes for common birds, in particular farmland birds, show significant declines, with no signs of recovery. Between 1990 and 2017, there was a decrease of 8 % in the index of common birds in the 25 EU Member States with bird population monitoring schemes and the United Kingdom. The decrease is slightly greater (11 %) if figures for Norway and Switzerland are included. The common forest bird index showed no decrease in the EU Member States plus the UK and a decline of 2 % when Norway and Switzerland were added. The decline in common farmland bird numbers was much more pronounced, at 33 % (EU) and 35 % (including Norway and Switzerland). While this indicator takes 1990 as a starting point, it should be borne in mind that significant decreases had already occurred before this date [1].
In spite of year-to-year fluctuations, which are typical features of butterfly populations, the index of grassland butterflies has declined significantly in the 15 EU countries with butterfly population monitoring schemes. In 2017, the index was 39 % below its 1990 value [11]. As with bird indices, the reductions observed since 1990 are on top of decreases before that time.
The long-term trends in common bird and grassland butterfly populations demonstrate that Europe has experienced a major decline in biodiversity. This has been primarily because of the loss, fragmentation and degradation of natural and semi-natural ecosystems, mainly caused by agricultural intensification [2, 5, 7], intensive forest management [9, 10] and land abandonment or urban sprawl [7, 8]. For example, through habitat loss, fragmentation and simplification (e.g. the removal of hedgerows and tree lines to make fields larger), birds lose their nesting sites and food sources, which adds to population decline [3, 4]. The main driver of the decline in grassland butterflies is the intensification of farming and change in rural land use, including the abandonment of grasslands. The loss of species-rich semi-natural grasslands has been particularly detrimental [8, 11]. Moreover, agricultural intensification can entail high inputs of agrochemicals, including pesticides, which can dramatically reduce insect — and butterfly — populations.
It continues to be a challenge to achieve the wide and effective deployment of conservation measures in European policies such as the Birds and the Habitats Directives, and the Water Framework Directive, as well as the environmental measures in the Common Agricultural Policy (CAP) designed to help populations recover at national and European scales.
It is difficult to forecast how soon biodiversity, as illustrated by the abundance of bird and grassland butterfly populations, will recover, as their state is influenced by a complex combination of environmental factors and policy measures. Positive impacts of the CAP reform and the measures anticipated under the Multi-Annual Financial Framework 2014-2020 on common species associated with farmland might become visible in the 2020-2030 period, as long as these policies are implemented thoroughly and on a large scale throughout the EU. On the other hand, other factors that could have adverse effects on the outlook beyond 2020 include the negative impact of climate change on biodiversity and ecosystems, particularly on those specialist species groups that are dependent on non-intensive agriculture and forest ecosystems. The increased competition for land could also intensify agricultural production in the EU through land take via urbanisation, as well as for the production of renewable energy and biofuels.
This indicator shows trends in the abundance of common birds and butterflies across their European ranges over time. It is a composite of many species trend indices. A value of 100 is set for each species in the start year. If a species is added to the composite index after the start year, it is scaled to the index value of the year it was added to the indicator.
The unit used is an index of relative values with the value for 1990 set to 100.
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 (updated in 2009/147/EC) and the Habitats Directive — 0043/1992.
Already in 2011, the first EU biodiversity strategy, Our life insurance, our natural capital: an EU biodiversity strategy to 2020, was adopted by the European Commission in line with the results of the 10th meeting of the Conference of the Parties to the Convention on Biological Diversity (CBD), held in Nagoya, Japan (October 2010). This provided a framework for the EU to meet its own biodiversity objectives and global commitments as a party to the CBD. The strategy, built around six mutually supportive targets that adress the main drivers of biodiversity loss, aimed to reduce the key pressures on nature and ecosystem services in the EU, but failed to reach its targets.
The publication of the new EU Biodiversity Strategy for 2030: Bringing nature back into our lives in May 2020 reinforces the relevance of this indicator, in particular through the commitments of the EU Nature Restoration Plan.
Moreover, this indicator needs to be seen in the context of the CAP, in particular its rural development policy 2014-2020, as well as the new Farm to Fork strategy. Relevant policy measures under the rural development policy include agri-environment-climate schemes and payments to farmers in areas with natural constraints or for adapted farming in areas with environmental restrictions, such as Natura 2000 sites.
EU 2020 Biodiversity Headline Target
a) Common birds
The data for this indicator originate from national monitoring data collected by the Pan-European Common Bird Monitoring Scheme (PECBMS). PECBMS is a partnership involving the European Bird Census Council, the Royal Society for the Protection of Birds, BirdLife International and Statistics Netherlands, which aims to deliver policy relevant biodiversity indicators for Europe. The PECBMS coordination unit is based in the Czech Society for Ornithology (CSO) in Prague, Czechia. The unit collects national indices, produces European indices and indicators, prepares outputs for publication, and communicates outputs to the public, policy makers and scientists.
Trend information spanning different time periods is derived from annual national breeding bird surveys in 28 European countries (EU-27 Member States except Croatia and Malta, plus Norway, Switzerland and the United Kingdom). Highly skilled volunteer ornithologists carry out counting and data collection. Data are collected nationally on an annual basis during the breeding season by common bird monitoring schemes. National bird monitoring data are gathered using several count methods (e.g. standardised point transects/line transects, territory mapping etc), using a variety of sampling strategies (from free choice of plots to stratified random sampling) and individual plot sizes vary within each country (from 1x1 km or 2x2 km squares or 2.5-degree grid squares to irregular polygons).
Indicators (multi-species indices) are computed using the MSI-tool (R-script) for calculating Multi-Species Indicators (MSI) and trends in MSIs. The method of calculation is described in Soldaat et al., 2017. Either European, EU or regional species indices including their standard errors are used as source data.
Country coverage (i.e. reflecting the availability of high-quality monitoring data from annually-operated common bird monitoring schemes employing generic survey methods and producing reliable national trends): Austria (since 1998), Belgium (Brussels since 1992; Flanders since 2007; Wallonia since 1990), Bulgaria (since 2005), Cyprus (since 2006), Czechia (since 1982), Denmark (since 1976), Estonia (since 1983), Finland (since 1975), France (since 1989), Germany (since 1989), Greece (since 2007), Hungary (since 1999), Ireland (since 1998), Italy (since 2000), Latvia (since 1995), Lithuania (since 2011), Luxembourg (since 2009), the Netherlands (since 1984), Norway (since 1996), Poland (since 2000), Portugal (since 2004), Romania (since 2007), Slovakia (since 2005), Slovenia (since 2008), Spain (since 1998), Sweden (since 1975), Switzerland (since 1999) and the United Kingdom (since 1966).
The current population index of common birds was produced for 168 species:
Common farmland birds:
Alauda arvensis, Alectoris rufa, Anthus campestris, Anthus pratensis, Bubulcus ibis, Burhinus oedicnemus, Calandrella brachydactyla, Carduelis cannabina, Ciconia ciconia, Corvus frugilegus, Emberiza cirlus, Emberiza citronella, Emberiza hortulana, Emberiza malanocephala, Falco tinnunculus, Galerida cristata, Galerida theklae, Hirundo rustica, Lanius collurio, Lanius minor, Lanius senator, Limosa limosa, Melanocorypha calandra, Miliaria calandra, Motacilla flava, Oenanthe hispanica, Passer montanus, Perdix perdix, Petronia petronia, Saxicola rubetra, Saxicola torquata, Serinus serinus, Streptopelia turtur, Sturnus unicolor, Sturnus vulgaris, Sylvia communis, Tetrax tetrax, Upupa epops, Vanellus vanellus.
Common forest birds:
Accipiter nisus, Anthus trivialis, Bombycilla garrulous, Bonasa bonasia, Carduelis spinus, Certhia brachydactyla, Certhia familiaris, Coccothraustes coccothraustes, Columba oenas, Cyanopica cyanus, Dendrocopos medius, Dendrocopos minor, Dryocopus martius, Emberiza rustica, Ficedula albicollis, Ficedula hypoleuca, Garrulus glandarius, Nucifraga caryocatactes, Parus ater, Parus cristatus, Parus montanus, Parus palustris, Phoenicurus phoenicurus, Phulloscopus bonelli, Phylloscopus collybita, Phylloscopus sibilatrix, Picus canus, Pyrrhula pyrrhula, Regulus ignicapilla, Regulus regulus, Serinus citrinella, Sitta europaea, Tringa ochropus, Turdus viscivorus.
Other common birds:
Acrocephalus arundinaceus, Acrocephalus palustris, Acrocephalus schoenobaenus, Acrocephalus scirpaceus, Actitis hypoleucus, Aegithalos caudatus, Alcedo atthis, Anas platyrhynchos, Apus apus, Ardea cinerea, Buteo buteo, Carduelis chloris, Carduelis flammea, Cettia cetti, Circus aeruginosus, Cisticola juncidis, Clamator glandarius, Columba palumbus, Corvus corax, Corvus corone, Corvus monedula, Cuculus canorus, Cygnus olor, Delichon urbica, Dendrocopos major, Dendrocopos syriacus, Egretta garzetta, Emberiza cia, Emberiza schoeniclus, Erithacus rubecula, Fringilla coelebs, Fringilla montifringilla, Fulica atra, Gallinago gallinago, Gallinula chloropus, Grus grus, Haematopus ostralegus, Hippolais icterina, Hippolais polyglotta, Hirundo daurica, Hirundo rupestris, Jynx torquilla, Larus ridibundus, Locustella fluviatilis, Locustella naevia, Lullula arborea, Luscinia luscinia, Luscinia megarhynchos, Luscinia svecica svecica, Merops apiaster, Motacilla alba, Motacilla cinerea, Muscicapa striata, Numenius arquata, Numenius phaeopus, Oenanthe cypriaca, Oenanthe oenanthe, Oriolus oriolus, Parus caeruleus, Parus major, Passer domesticus, Phasianus colchicus, Phoenicurus ochruros, Phylloscopus trochilus, Pica pica, Picus viridis, Pluvialis apricaria, Podiceps cristatus, Prunella modularis, Pyrrhocorax pyrrhocorax, Streptopylia decaocto, Sylvia atricapilla, Sylvia borin, Sylvia cantillans, Sylvia curruca, Sylvia hortensis, Sylvia melanocephala, Sylvia melanothorax, Sylvia nisoria, Sylvia undata, Tachybaptus ruficollis, Tadorna tadorna, Tetrao tetrix, Tringa erythropus, Tringa glareola, Tringa nebularia, Tringa tetanus, Troglodytes troglodytes, Turdus iliacus, Turdus merula, Turdus philomelos, Turdus pilaris, Turdus torquatus.
More information about species indices and trends is available at: https://www.ebcc.info/pecbms/
Rationale for species selection:
The PECBMS European species classification (farmland, forest and other) has been developed over time as the indicators have been published and refined. The first publication was based on European trends of 47 common bird species, classified by national coordinators of monitoring schemes and other experts who met at the PECBMS workshop in Prague in 2001. For the second publication, based on an enlarged species sample, the classification was improved and was based on a publication by Tucker and Evans (1997), describing habitats and their importance for birds in Europe. Since 2007, when the third set of European indices and indicators was published, data on over 150 species have been used and the species classification has been based on assessments within bio-geographical regions in Europe. (See the PECBMS website for further details on the historic classification).
b) Butterflies
The data for this indicator originate from the European Butterfly Monitoring Scheme (eBMS) (a joint initiative of Butterfly Conservation Europe and the Centre for Ecology & Hydrology) and the Assessing ButterfLies in Europe (ABLE) project.
The butterfly sampling method is based on Butterfly Transect Counts (Pollard and Yates, 1993). The eBMS provides methodological support to volunteers and country/regional networks, e.g. via the Manual for Butterfly Transect Counts.
The butterfly Indicator is based on the fieldwork of thousands of trained professional and volunteer recorders, counting butterflies on more than 6 200 transects scattered widely across the European Union under standardised conditions. National coordinators collect the data and perform the first quality control. In 2017, more than 55 880 km of transect walks were made, more than 90 % of them by volunteers, monitoring each transect an average of 15 times per year (Van Swaay et al., 2017).
For each species and year, flight periods were estimated (Dennis et al., 2016) based on climate zones as defined in Metzger et al. (2013), but with further geographic stratification to represent major geographic units (e.g. the UK and Ireland were treated as a separate unit to continental Europe). Site level indices were produced by estimating the missing counts, and species’ collated indices were produced for each monitoring scheme using a Poisson General Linear Model (GLM) with site and year effects, as well as the proportion of the flight period surveyed as a weighting. A collated index for the EU was produced for each species by fitting a Poisson GLM to the scheme-level collated indices with scheme and year effects as well as a weighting. The EU indices for the 17 species were combined by taking the geometric mean of the indices using the BRC indicators R package (August et al., 2017). This indicator is a unified measure of biodiversity following the bird indicators as described by Gregory et al. (2005), by averaging indices of species rather than abundances in order to give each species an equal weight in the resulting indicators. When positive and negative changes of indices are in balance, then their mean would be expected to remain stable. If more species decline than increase, the mean should go down and vice versa. Thus, the index mean is considered a measure of biodiversity change.
For this updated indicator, data were used from 16 countries: Andorra, Belgium, Estonia, Finland, France, Germany, Ireland, Latvia, Lithuania, Luxembourg, Romania, Slovenia, Spain, Sweden, the Netherlands and the United Kingdom. The indicator included data from 19 butterfly monitoring schemes in total; Spain has three schemes — Catalonia, Basque Country and other parts of Spain; and Belgium has two (Flanders and Wallonia). Although there is a dataset available from Madeira, none of the grassland butterfly indicator species occurs on this island.
The indicator is based on the following 17 species:
Widespread species: Anthocharis cardamines, Coenonympha pamphilus, Lasiommata megera, Lycaena phlaeas, Maniola jurtina, Ochlodes sylvanus and Polyommatus icarus.
Specialist species: Cupido minimus, Cyaniris semiargus, Erynnis tages, Euphydryas aurinia, Lysandra bellargus, Lysandra coridon, Phengaris arion, Phengaris nausithous, Spialia sertorius and Thymelicus acteon.
Rationale for species selection:
European butterfly experts selected 17 species they considered to be characteristic of European grassland and which occurred in a large part of Europe, covered by the majority of the butterfly monitoring schemes, and having grasslands as their main habitat (Van Swaay et al., 2006).
A Monte Carlo method is used to account for sampling error and when not all yearly index numbers of all species are available. The MSI-tool (R-script) is used to calculate Multi-Species Indicators (MSI) and trends in MSIs.
The indicator is accompanied by measures of uncertainty, including smoothed trends and confidence limits (at 95 % level).
Data on population development of a species are assessed by calculating yearly indices and standard errors using the TRIM software (Pannekoek and Van Strien, 2005, http://www.bc-europe.eu/upload/EurButtInd/trim3man.pdf)
MAIN DISADVANTAGES OF THE INDICATOR
a. Common birds
b. Butterflies
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/abundance-and-distribution-of-selected-species-8/assessment-1 or scan the QR code.
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