Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Habitatrichtlijnrapportage 2019: Annex B Habitatrichtlijnsoorten : Achtergronddocument
    Bos-Groenendijk, G.I. ; Swaay, C.A.M. van - \ 2020
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 170) - 59
    This background document explains the process of preparing the Annex B report (Habitats Directive species) for the reporting period 2013–2018, with data from the period 2012-2017. Article 17 of the EU Habitats Directive requires Member States to submit a progress report every six years. The conservation status of all 81 Habitats Directive species (Annex II, IV and V) has been established according to the evaluation matrix prescribed by the European Commission. The report describes the reporting process and explains the decisions made by the species experts when filling in the report formats. The conservation status of each species was assessed for the following parameters: range, population, habitat and future prospects.
    Vogel- en Habitatrichtlijnrapportage 2019
    Adams, Annemiek ; Bijlsma, Rienk-Jan ; Bos, Gerdien ; Clerkx, Sandra ; Janssen, John ; Kleunen, André van; Remmelts, Wilmar ; Rooijen, Nils van; Schaminée, Joop ; Schmidt, Anne ; Swaay, Chris van; Wijnhoven, Sander ; Woestenburg, Martin ; Aar, Mies van - \ 2020
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (Thema Informatievoorziening Natuur / Wettelijke Onderzoekstaken Natuur & Milieu ) - 52
    Over a century of data reveal more than 80% decline in butterflies in the Netherlands
    Strien, Arco J. van; Swaay, Chris A.M. van; Strien-van Liempt, Willy T.F.H. van; Poot, Martin J.M. ; WallisDeVries, Michiel F. - \ 2019
    Biological Conservation 234 (2019). - ISSN 0006-3207 - p. 116 - 122.
    Bayesian inference - Distribution - JAGS - List length analysis - Living Planet Index - Monitoring

    Opportunistic butterfly records from 1890 to 2017 were analysed to quantitatively estimate the overall long-term change in occurrence of butterfly species in the Netherlands. For 71 species, we assessed trends in the number of occupied 5 km × 5 km sites by applying a modified List Length method, which takes into account changes in observation effort. We summarised the species trends in a Multi-Species Indicator (MSI) by taking the geometric mean of the species indices. Between 1890–1930 and 1981–1990, the MSI decreased by 67%; downward trends were detected for 42 species, many of which have disappeared completely from the Netherlands. Monitoring count data available from 1992 showed a further 50% decline in MSI. Combined, this yields an estimated decline of 84% in 1890–2017. We argue that in reality the loss is likely even higher. We also assessed separate MSIs for three major butterfly habitat types in the Netherlands: grassland, woodland and heathland. Butterflies strongly declined in all three habitats alike. The trend has stabilised over recent decades in grassland and woodland, but the decline continues in heathland.

    Standaard Data Formulieren Natura 2000-gebieden : aanvullingen vanwege wijzigingen in Natura 2000-aanwijzingsbesluiten
    Bos-Groenendijk, G.J. ; Swaay, C.A.M. van; Schmidt, A.M. - \ 2018
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu (WOt-technical report 114) - 52
    This report explains the additional information on the Standard Data Forms for species listed in Annex II of the Habitats Directive. These forms make up part of the database of information on Natura 2000 sites. The database can be used as material evidence in legal proceedings and is used by the European Commission when assessing proposals for Natura 2000 sites. In 2017 an analysis was made of present but not designated conservation values for habitats and species under the Habitats Directive. The analysis identified 74 species-site combinations to be added to designation orders for Natura 2000 sites. Information on these combinations has been entered onto the Standard Data Forms, including data on the numbers of a species, the type of population, the relative population compared with other populations in the Netherlands, species habitat quality, the location of the population within the European range and a general evaluation. The assessments of the sites for each species were made by experts
    Ecological determinants of butterfly vulnerability across the European continent
    Essens, Tijl ; Langevelde, Frank van; Vos, Rutger A. ; Swaay, Chris A.M. van; Wallis de Vries, Michiel - \ 2017
    Journal of Insect Conservation 21 (2017)3. - ISSN 1366-638X - p. 439 - 450.
    Butterflies - Conservation - Life-history traits - Phylogeny - Red List - Vulnerability

    In drawing up Red Lists, the extinction risks of butterflies and other insects are currently assessed mainly by using information on trends in distribution and abundance. Incorporating information on species traits may increase our ability to predict species responses to environmental change and, hence, their vulnerability. We summarized ecologically relevant life-history and climatic niche traits in principal components, and used these to explain the variation in five vulnerability indicators (Red List status, Endemicity, Range size, Habitat specialisation index, Affinity for natural habitats) for 397 European butterfly species out of 482 species present in Europe. We also evaluated a selection of 238 species to test whether phylogenetic correction affected these relationships. For all but the affinity for natural habitats, climatic niche traits predicted more variation in vulnerability than life-history traits; phylogenetic correction had no relevant influence on the findings. The life-history trait component reflecting mobility, development rate, and overwintering stage, proved the major non-climatic determinant of species vulnerability. We propose that this trait component offers a preferable alternative to the frequently used, but ecologically confusing generalist-specialist continuum. Our analysis contributes to the development of trait-based approaches to prioritise vulnerable species for conservation at a European scale. Further regional scale analyses are recommended to improve our understanding of the biological basis of species vulnerability.

    A nitrogen index to track changes in butterfly species assemblages under nitrogen deposition
    Wallis de Vries, Michiel ; Swaay, Chris A.M. van - \ 2017
    Biological Conservation 212 (2017)pt. B. - ISSN 0006-3207 - p. 448 - 453.
    Biodiversity - Butterflies - Global change - Indicators - Insects - Nitrogen deposition
    The impacts of nitrogen deposition (N) on animal communities are still poorly understood in comparison to plant communities. Long-term monitoring of community changes may contribute to this understanding, complementing experimental studies on underlying mechanisms. Butterflies are particularly suitable for such analyses, because the different species cover a broad gradient of productivity, their ecological traits are well-known, monitoring data are available in a growing number of countries, and the short life history of butterflies ensures a rapid response to changing environmental conditions.Here, we use species-specific nitrogen optima to develop a community nitrogen index (CNI) for butterflies in the Netherlands. Over a 25-year period (1990-2015), data from the Dutch Butterfly Monitoring Scheme reveal a significant increase in the CNI in response to high nitrogen deposition levels. However, the rate of increase is declining, in close parallel with reduced nitrogen deposition loads. The continuing increase indicates that nitrogen deposition still exceeds the critical nitrogen load of butterfly communities in the Netherlands. Overall, the relative increase of butterflies from more productive environments reflects the advantage, under high nitrogen availability, of mobile and multivoltine species with high reproductive capacity, rapid larval development and hibernation as pupae or adults. We discuss the perspectives and limitations in applying the CNI at both national and local scales. We propose that, when taking the critical nitrogen load of the examined butterfly community into account, the CNI may prove a valuable tool to track changes of biotic communities in relation to nitrogen deposition.
    Bioscore 2.0 : a species-by-species model to assess anthropogenic impacts on terrestrial biodiversity in Europe
    Clement, Jan ; Hendriks, Marjon ; Marco, Moreno Di; Hennekens, Stephan ; Hinsberg, Arjen van; Huijbregts, Mark ; Janssen, Peter ; Kampichler, Christian ; Knegt, Bart de; Knol, Onno ; Mylius, Sido ; Ozinga, Wim ; Pouwels, Rogiere ; Rondinini, Carlo ; Santini, Luca ; Schaminée, Joop ; Schipper, Aafke ; Sierdsema, Henk ; Swaay, Chris van; Tol, Sandy van; Visser, Hans ; Wiertz, Jaap - \ 2016
    The Hague : PBL Netherlands Environmental Assessment Agency - 95
    How much Biodiversity is in Natura 2000? : the “Umbrella Effect” of the European Natura 2000 protected area network : technical report
    Sluis, T. van der; Foppen, R. ; Gillings, Simon ; Groen, T.A. ; Henkens, R.J.H.G. ; Hennekens, S.M. ; Huskens, K. ; Noble, David ; Ottburg, F.G.W.A. ; Santini, L. ; Sierdsema, H. ; Kleunen, A. van; Schaminee, J.H.J. ; Swaay, C. van; Toxopeus, Bert ; Wallis de Vries, M.F. ; Jones-Walters, L.M. - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2738) - 147
    biodiversity - habitats directive - birds directive - natura 2000 - statistical analysis - geographical information systems - biodiversiteit - habitatrichtlijn - vogelrichtlijn - natura 2000 - statistische analyse - geografische informatiesystemen
    In order to assess the significance of the presumed “umbrella effect” of Natura 2000 areas the European Commission initiated a study, in 2013, to address the following questions: 1) Which are, amongst the species regularly occurring within the European territory of the EU-28 Member States, those that significantly benefit from the site conservation under the EU Birds and Habitats Directive? 2) What is the percentage of all species occurring in the wild in the EU that benefit significantly from Natura 2000? 3) How significant is the contribution of Natura 2000 in relation to the objective of halting and reversing biodiversity loss? The approach used existing data, and covered the terrestrial mammals, birds, reptiles, amphibian, butterfly and plant species. The analysis is mostly based on statistical distribution models and GIS processing of species distribution data in relation to their presence within protected areas of the Natura 2000 network. The main findings for all species groups were: Animal species for which Natura 2000 areas were not specifically designated occur more frequently inside Natura 2000 than outside (in particular breeding birds and butterflies). These species do, therefore, gain benefit from the protected areas network. The species for which Natura 2000 areas were designated generally occur more frequently within the Natura 2000 site boundaries than the nonannex species; this is in particular the case for birds and butterflies, for amphibians and reptiles the difference is negligible. More specific conclusions and findings, as well as discussion of these results and implications for further studies are included in the report.
    The “Umbrella Effect” of the Natura 2000 network : an assessment of species inside and outside the European Natura 2000 protected area network : executive summary
    Jones-Walters, L.M. ; Gillings, Simon ; Groen, T.A. ; Hennekens, S.M. ; Noble, David ; Huskens, K. ; Santini, L. ; Sierdsema, H. ; Kleunen, A. van; Swaay, C. van; Sluis, T. van der - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 273A) - 11
    biodiversity - natura 2000 - birds directive - habitats directive - biogeography - biodiversiteit - natura 2000 - vogelrichtlijn - habitatrichtlijn - biogeografie
    De betekenis van Fryslân voor de instandhouding van soorten en habitattypen : toelichting op de totstandkoming van de tabellen die als hulpmiddel dienen voor het beoordelen van de betekenis van provinsje Fryslân voor de instandhouding van soorten en habitattypen onder de nieuwe Wet natuurbescherming
    Bink, R.J. ; Schmidt, A.M. ; Vreeswijk, Tessa van; Swaay, C.A.M. van; Turnhout, C.A.M. van; Verweij, R. ; Woltjer, I. ; Broekmeyer, M.E.A. ; Soldaat, L. - \ 2016
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2734) - 27
    natuurbeschermingsrecht - natuurbescherming - habitatrichtlijn - vogelrichtlijn - natura 2000 - habitats - soorten - friesland - nature conservation law - nature conservation - habitats directive - birds directive - natura 2000 - habitats - species - friesland
    Op 1 januari 2017 wordt de nieuwe Wet natuurbescherming van kracht. De provincies krijgen door deze wet een grotere verantwoordelijkheid voor het beschermen en in stand houden van vele soorten en habitattypen. Elke provincie moet daartoe een provinciale natuurvisie opstellen die door Provinciale Staten wordt vastgesteld en door Gedeputeerde Staten uitgevoerd. De provinsje Fryslân stelt zich de vraag wat de betekenis is van de provinsje voor de instandhouding van de soorten en habitattypen in Nederland onder de Wet natuurbescherming. Het antwoord op deze vraag wordt gebruikt voor twee doeleinden: een goede inzet van beleid en instrumentarium en – daar waar mogelijk – het gebruik van vrijstellingen bij de vergunningverlening. Beide zullen worden uitgewerkt in de natuurvisie van Fryslân. De provinsje Fryslân wil daartoe over een hulpmiddel beschikken waarmee zij de betekenis van de provinsje kan bepalen. Alterra, het Centraal Bureau voor Statistiek (CBS), Sovon vogelonderzoek Nederland, de Vlinderstichting en andere PGO’s hebben gezamenlijk gewerkt aan dat hulpmiddel. Het resultaat is een aantal tabellen (Excelbestand) met een toelichtend rapport.
    Exploring spatial indicators for biodiversity accounting
    Remme, Roy P. ; Hein, Lars ; Swaay, Chris A.M. van - \ 2016
    Ecological Indicators 70 (2016). - ISSN 1470-160X - p. 232 - 248.
    Biodiversity indicators - Criteria - Ecosystem accounting - Monitoring - SEEA-EEA - Spatial analysis

    In the context of the System for Environmental-Economic Accounting, biodiversity accounting is being developed as a tool to monitor and increase the understanding of human impacts on biodiversity. Biodiversity accounting aims to structurally measure, monitor and map changes in multiple biodiversity components, as an integral part of a larger system of ecosystem accounts. Both indicators relevant for ecosystem functioning and indicators that reflect the non-use values of biodiversity can be included in biodiversity accounting. In this paper we focus on the latter, and we test the potential applicability of a set of species indicators for developing a biodiversity account in Limburg province, the Netherlands. In particular, we map and analyse a range of indicators reflecting species richness, the presence of rare and threatened species and species diversity. We test spatial correlation to identify the minimum set of indicators that would need to be included in the account. We also evaluate individual indicators using eight different criteria. We show that, in Limburg province, a set of indicators covering at least five species groups is required, and that it would be most meaningful to have indicators reflecting the occurrence of threatened species. However, data availability as well as the most suitable set of indicators are likely to differ between areas, and case studies in other countries are required to support the selection of indicators for biodiversity accounting in an international framework.

    Naar een samenhangend monitoring- en beoordelingssysteem voor het natuurbeleid : Deel I. Evaluatie van de bruikbaarheid van gegevens van de Werkwijze Monitoring en Beoordeling Natuurnetwerk en Natura 2000/PAS voor de Europese rapportages
    Schmidt, A.M. ; Bijlsma, R.J. ; Soldaat, L. ; Turnhout, C.A.M. van; Swaay, C.A.M. van; Zoetebier, T.K.G. ; Woltjer, I. - \ 2015
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2645) - 69
    vogelrichtlijn - habitatrichtlijn - natura 2000 - eu regelingen - monitoring - ecologische hoofdstructuur - intensieve veehouderij - emissiereductie - birds directive - habitats directive - natura 2000 - eu regulations - monitoring - ecological network - intensive livestock farming - emission reduction
    In dit rapport worden de resultaten van de evaluatie van de bruikbaarheid van de gegevens van de Werkwijze Monitoring en Beoordeling Natuur (WMBN) voor de EU-rapportages beschreven. Geconcludeerd is dat de gegevens van de WMBN voor de meetdoelen t.a.v. van de kwaliteit van habitattypen en leefgebieden van VR- en HR-soorten goed bruikbaar zijn, maar dat er nog wel wat verbeteringen wenselijk zijn. Voor de meetdoelen t.a.v. van VR- en HR-soorten is de WMBN minder geschikt en zullen ook in de toekomst de gegevens van het Netwerk Ecologische Monitoring (NEM), aangevuld met gegevens van andere monitoringprogramma’s zoals die van Rijkswaterstaat en IMARES, nodig zijn. Aanbevelingen worden gedaan ter verbetering.
    Gunstige referentiewaarden voor populatieomvang en verspreidingsgebied van soorten van bijlage II, IV en V van de Habitatrichtlijn
    Ottburg, F.G.W.A. ; Swaay, C.A.M. van - \ 2014
    Wageningen : Wettelijke Onderzoekstaken Natuur & Milieu, Wageningen UR (WOt-rapport 124)
    amphibia - lepidoptera - vissen - zoogdieren - ongewervelde dieren - mossen - korstmossen - reptielen - populatiebiologie - habitatrichtlijn - amphibia - lepidoptera - fishes - mammals - invertebrates - mosses - lichens - reptiles - population biology - habitats directive
    This report presents the Favourable Reference Values for population size and range for the species listed in Annexes II, IV and V of the EU Habitats Directive. These reference values are used to assess the conservation status of species as required by Article 17 of the Habitats Directive. They were determined according to a protocol (checklist) and based on scientific information. Where the required scientific information was not readily available, expert judgement was used to fill the gaps. When determining the reference values, experts on each of the species groups were enlisted from the various voluntary conservation organisations, IMARES Wageningen UR (Texel and IJmuiden) and Alterra Wageningen UR. In addition, two extra questions were answered on how these reference values can be maintained or achieved, and the potential influence of climate warming.
    BioScore 2.0. Tussenrapportage WOT-04-011-036.50
    Hinsberg, A. van; Hendriks, M. ; Hennekens, S.M. ; Sierdsema, H. ; Swaay, C. van; Rondinini, C. ; Santini, L. ; Delbaere, B. ; Knol, O.M. ; Wiertz, J. - \ 2014
    Wageningen : Wettelijke Onderzoekstaken Natuur en Milieu (WOt-interne notitie 87)
    Biodiversiteitsgraadmeters Noord-Holland : status en trend van ecosystemen en soorten
    Greft-van Rossum, J.G.M. van der; Knegt, B. de; Wamelink, G.W.W. ; Clement, J. ; Frissel, J.Y. ; Pouwels, R. ; Puijenbroek, P. van; Sanders, M.E. ; Sparrius, L.B. ; Swaay, C.A.M. van; Wegman, R.M.A. - \ 2014
    Wageningen : Alterra, Wageningen-UR (Alterra-rapport 2543) - 78
    biodiversiteit - ecosystemen - vegetatietypen - fauna - lepidoptera - natuurwaarde - inventarisaties - noord-holland - biodiversity - ecosystems - vegetation types - fauna - lepidoptera - natural value - inventories - noord-holland
    Ondanks het ontbreken van kwantitatieve doelen voor natuurbehoud voor de provincie Noord-Holland kan vastgesteld worden dat het strategische doel van behoud en herstel van de biodiversiteit in de provincie momenteel niet gehaald wordt. De gemiddelde populatieomvang Rode Lijstsoorten is in de provincie Noord-Holland in 2013 gedaald tot 25% van het niveau ten opzichte van 1990. De huidige natuurkwaliteit van ecosystemen varieert tussen 30% en 55% ten opzichte van een ongestoorde situatie. De natuurkwaliteit van het agrarisch gebied, ten opzichte van 1970, bedraagt nog 40%. Deze mag niet direct worden vergeleken met de natuurkwaliteit van ecosystemen, vanwege een andere referentie. Het blijkt dat de totale voorraad biodiversiteit (als product van de oppervlakte natuur en de kwaliteit) is teruggelopen van 41% in 1900, via 26% halverwege de 20e eeuw tot 15% in de huidige situatie. Het areaal natuur neemt weer toe. De provincie Noord-Holland heeft in de beleidsagenda ‘Licht op Groen’ behoud en herstel van biodiversiteit als hoogste doel van het provinciale natuurbeleid geformuleerd. Om het beleid te kunnen monitoren en evalueren heeft Alterra een compacte set biodiversiteitsgraadmeters ontwikkeld die toestand en trend weergeven van biodiversiteit in Noord-Holland op strategisch niveau. Daarnaast worden knelpunten in ruimtelijke en milieucondities weergegeven die (mede) oorzaak zijn van het biodiversiteitsverlies.
    Tracking butterflies for effective conservation
    Swaay, C.A.M. van - \ 2014
    Wageningen University. Promotor(en): Michiel Wallis de Vries; Marcel Dicke. - Wageningen : Wageningen University - ISBN 9789461739988 - 218
    lepidoptera - zoögeografie - biogeografie - populatiedynamica - natuurbescherming - monitoring - nederland - europa - lepidoptera - zoogeography - biogeography - population dynamics - nature conservation - monitoring - netherlands - europe
    Dit proefschrift bestaat uit drie delen: het volgen van veranderingen in de verspreiding van vlinders, het volgen van veranderingen in de populatiegrootte van vlinders en hoe deze kennis te gebruiken voor hun bescherming.
    Effects of local variation in nitrogen deposition on butterfly trends in The Netherlands
    Wallis de Vries, M.F. ; Swaay, C.A.M. van - \ 2013
    Proceedings of the Netherlands Entomological Society meeting 24 (2013). - ISSN 1874-9542 - p. 25 - 33.
    lepidoptera - fauna - stikstof - ammoniakemissie - nederland - nitrogen - ammonia emission - netherlands
    Anthropogenic nitrogen deposition has been recognized as a factor affecting the dynamics and composition of plant communities. Its impact on insect communities is still largely unknown. Using data from the Dutch Butterfly Monitoring Scheme, we analyzed the variation in local trends of butterfly abundance in three Natura 2000 habitat types of known sensitivity to nitrogen deposition: coastal dunes (H2130), wet heathlands (H4010A) and species-rich Nardus grassland (H6230). We found evidence of a negative impact of increasing levels of nitrogen deposition on butterfly trends in all three habitat types. Interestingly, species from more nitrogen-rich habitats showed a similar, though less pronounced, response. The results constitute the first evidence of a significant dose-response relationship between nitrogen deposition and declines in insect abundance at a national scale.
    Biodiversiteitsgraadmeters Fryslân : status en trend van hoofd-natuurtypen en soorten
    Knegt, B. de; Wamelink, G.W.W. ; Adrichem, M.H.C. van; Clement, J. ; Puijenbroek, P. ; Sparrius, L. ; Swaay, C. van - \ 2013
    Wageningen : Alterra (Alterra-rapport 2431) - 60
    natuurwaarde - biodiversiteit - ecosystemen - flora - fauna - natuurgebieden - oppervlakte (areaal) - friesland - natural value - biodiversity - ecosystems - flora - fauna - natural areas - acreage - friesland
    De graadmeter bestaat uit twee delen, een deel bevat informatie over de voor- of achteruitgang van soorten (zoals vogels, vlinders en zoogdieren), het tweede deel bevat informatie over de natuurkwaliteit en het oppervlak natuur. Informatie van soorten en de natuurkwaliteit is gebaseerd op veldwaarnemingen. Zowel de natuurkwaliteit als het oppervlak natuur worden vergeleken met een ongestoorde situatie. Voor het agrarisch gebied is een aparte referentie gebruikt. De gebruikte methode maakt het mogelijk om de Friese situatie qua biodiversiteit te spiegelen aan het verleden en aan de landelijke situatie. Het aandeel van het Friese grondgebied met min of meer natuurlijke ecosystemen, exclusief (half)natuurlijk grasland, bedraagt nu circa 48%. De toename in de oppervlakte natuur is sinds de introductie van de EHS in Fryslân groter dan landelijk
    Correspondence: Uncertainty in thermal tolerances and climatic debt
    Devictor, V. ; Swaay, C. van; Brereton, T. ; Brotons, L. ; Chamberlain, D. ; Heliölä, J. ; Herrando, S. ; Julliard, R. ; Kuussaari, M. ; Lindström, A. ; Reif, J. ; Roy, D.B. ; Schweiger, O. ; Settele, J. ; Stefanescu, C. ; Strien, A. van; Turnhout, C. van; Vermouzek, Z. ; Wallis de Vries, M.F. ; Wynhoff, I. ; Jiguet, F. - \ 2012
    Nature Climate Change 2 (2012). - ISSN 1758-678X - p. 638 - 639.
    Changes in nectar supply: A possible cause of widespread butterfly decline
    Wallis de Vries, M.F. ; Swaay, C.A.M. van; Plate, C.L. - \ 2012
    Current Zoology 58 (2012)3. - ISSN 1674-5507 - p. 384 - 391.
    species richness - field margins - agricultural landscapes - conservation - pollination - vegetation - diversity - scale - biodiversity - grasslands
    Recent studies have documented declining trends of various groups of flower-visiting insects, even common butterfly species. Causes of these declines are still unclear but the loss of habitat quality across the wider countryside is thought to be a major factor. Nectar supply constitutes one of the main resources determining habitat quality. Yet, data on changes in nectar abundance are lacking. In this study, we provide the first analysis of changes in floral nectar abundance on a national scale and link these data to trends in butterfly species richness and abundance. We used transect data from the Dutch Butterfly Monitoring Scheme to compare two time periods: 1994-1995 and 2007-2008. The results show that butterfly decline can indeed be linked to a substantial decline in overall flower abundance and specific nectar plants, such as thistles. The decline is as severe in reported flower generalists as in flower specialists. We suggest that eutrophication is a main cause of the decline of nectar sources [Current Zoology 58 (3): 384-391, 2012].
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