Original Paper

Biodiversity and Conservation

, Volume 22, Issue 3, pp 673-686

First online:

Occupancy modelling as a new approach to assess supranational trends using opportunistic data: a pilot study for the damselfly Calopteryx splendens

  • Arco J. van StrienAffiliated withStatistics NetherlandsInstitute for Biodiversity and Ecosystem Dynamics, University of Amsterdam Email author 
  • , Tim TermaatAffiliated withDutch Butterfly Conservation
  • , Vincent KalkmanAffiliated withEuropean Invertebrate Survey—the Netherlands, Nationaal Natuurhistorisch Museum, Naturalis
  • , Marijn PrinsAffiliated withDutch Butterfly Conservation
  • , Geert De KnijfAffiliated withResearch Institute for Nature and Forest
  • , Anne-Laure GourmandAffiliated withMuséum National d’Histoire Naturelle, UMR 7204, CERSP ‘Conservation des Espèces, Restauration et Suivi des Populations’
  • , Xavier HouardAffiliated withCentre Entomologique de Ressources pour la Conservation, Office pour les insectes et leur environnement (Opie)
  • , Brian NelsonAffiliated withNational Parks and Wildlife Service
  • , Calijn PlateAffiliated withStatistics Netherlands
    • , Stephen PrenticeAffiliated withBritish Dragonfly Society, c/o Natural England, Parkside Court
    • , Eugenie ReganAffiliated withNational Biodiversity Data Centre
    • , David SmallshireAffiliated withBritish Dragonfly Society
    • , Cédric VanappelghemAffiliated withUniversité de Lille 1, Laboratoire GEPV UMR CNRS 8198
    • , Wouter VanreuselAffiliated withNatuurpunt

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There is limited information available on changes in biodiversity at the European scale, because there is a lack of data from standardised monitoring for most species groups. However, a great number of observations made without a standardised field protocol is available in many countries for many species. Such opportunistic data offer an alternative source of information, but unfortunately such data suffer from non-standardised observation effort and geographical bias. Here we describe a new approach to compiling supranational trends using opportunistic data which adjusts for these two major imperfections. The non-standardised observation effort is dealt with by occupancy modelling, and the unequal geographical distribution of sites by a weighting procedure. The damselfly Calopteryx splendens was chosen as our test species. The data were collected from five countries (Ireland, Great Britain, the Netherlands, Belgium and France), covering the period 1990–2008. We used occupancy models to estimate the annual number of occupied 1 × 1 km sites per country. Occupancy models use presence-absence data, account for imperfect detection of species, and thereby correct for between-year variability in observation effort. The occupancy models were run per country in a Bayesian mode of inference using JAGS. The occupancy estimates per country were then aggregated to assess the supranational trend in the number of occupied 1 × 1 km2. To adjust for the unequal geographical distribution of surveyed sites, we weighted the countries according to the number of sites surveyed and the range of the species per country. The distribution of C. splendens has increased significantly in the combined five countries. Our trial demonstrated that a supranational trend in distribution can be derived from opportunistic data, while adjusting for observation effort and geographical bias. This opens new perspectives for international monitoring of biodiversity.


Detection Monitoring Distribution Citizen science data Odonata JAGS