The Dutch Butterfly Monitoring Scheme consists of two parts: population abundance monitoring and species distribution monitoring. Coordination of both parts is in the hands of Dutch Butterfly Conservation with observations collected by many volunteers working for DBC and land management organisations. Statistics Netherlands (CBS) checks and analyses the data in relation to the monitoring targets set and makes recommendations for improvements in the monitoring scheme on the basis of annual quality reporting in the framework of the Dutch Network Ecological Monitoring (NEM), commissioned by the Dutch Ministry of Agriculture, Nature and Food Quality.
Population abundance monitoring network
Counts are performed on a weekly basis for all species on transects (fixed routes) with an average length of 1km and during the flight season, typically from March through September. In addition, transects are used which feature counts for one particular species (single species transects). These mainly apply in regard to species which are relevant under the European Birds and habitats Directive (BHD) for which protected areas have been designated or which are difficult to count as adult butterflies along transects.
Species distribution monitoring
Many butterfly data are collected without the use of a set measuring protocol; in the form of nomenclatural lists or by separate counts of a single species. These observational data are recorded by observers onto the available internet portals (landkaartje.vlinderstichting.nl, waarneming.nl and telmee.nl). All observations are gathered in the Dutch National Database Flora and Fauna (NDFF) and analysed by CBS. Up-to-date information on and trends in species distribution are determined by routine application of so-called occupancy models. These models are equally useful for research purposes to assess whether sufficient monitoring took place on particular sites to locate distinct species. In addition, targeted research is carried out that should yield a more comprehensive inventory of the actual and potential site distribution of a number of species found in sensitive or inaccessible areas.
The NDFF is a national data warehouse in which ecological data on the Netherlands are compiled, systematised and validated. The data form a picture of what is known about the distribution of flora and fauna species. The NDFF stores well over 100 million observations.