About CWRnl


Crop domain

CWRnl focusses on the economically most important agricultural and horticultural crops. For crops important at the global scale, the world primary crop list of the Food and Agriculture Organization of the United Nations was used. This list was supplemented with crops of economic importance to the Netherlands based on data about crop production areas published by Statistics Netherlands combined with data about economic revenues per hectare published by Wageningen Economic Research. The list was further supplemented with crops or taxa included in Annex 1 of the International Treaty on Plant Genetic Resources for Food and Agriculture and crops occurring in the European Union database of registered plant varieties or the Dutch variety list of the Netherlands Inspection Service for Horticulture. Because of the focus on agricultural and horticultural crops, the inventory does not include species that may be relevant to other crop domains, such as forestry, ornamentals or medicinal crops.

CWR inventory

Based on the botanical genus name of a crop, the ‘Verspreidingsatlas’ of Floristic Research, the Netherlands (accessed 14-10-2014) was used to examine which taxa of the genus occur in the Netherlands. Synonyms, non-accepted names and combinations of taxa, as indicated by the ‘Verspreidingsatlas’, were disregarded. Relevant information, including data on indigeneity, occurrence and Red List status were also obtained from the ‘Verspreidingsatlas’. In case of missing data, information was obtained from the Dutch Species Register, the website ‘Wild Plants in the Netherlands and Belgium’ and Heukels’ Flora of the Netherlands. A total number of 453 CWR were identified, of which 214 were described as endemic or introduced to the Netherlands before the year 1900. These 214 taxa, of which 53 with Red List status, were included in CWRnl.

Crop relationship

Species of the same genus generally show a different degree of relationship with the cultivated crop. As a result, some species can be crossed more easily with the crop species than others. Evidently, the lower the crossing barrier, the higher the importance of the species. The ‘Harlan and de Wet Crop Wild Relative Inventory’ of the Global Crop Diversity Trust was used to collect information on crop relationship. This information service classifies species according to the so-called ‘gene pool’ concept, consisting of the primary (excellent crossability), secondary (intermediate crossability) and tertiary (difficult crossability) gene pool. For crops that have not yet been described according to the gene pool concept, the Inventory uses the ‘taxon group’ concept, where species with a lower taxon group number (1-5) are taxonomically more related with the cultivated crop. For species without gene pool or taxon group information, the crop relationship on CWRnl is denoted by ‘same genus’. Because inter-fertility is not necessarily limited to species of the same genus, the Harlan and de Wet Crop Wild Relative Inventory was also used to identify CWR from other genera than that of the cultivated crop, which then were added to our inventory.


Detailed distribution data spanning the period 2000-2015 were collected from the National Databank Flora and Fauna (NDFF, accessed 2-4-2015) for the 53 identified Red List CWR. These data included their occurrence and abundance per 1km x 1km square, the percentage overlap of the squares with areas belonging to the Dutch network of protected areas and the presence of species in areas of the Society for the Preservation of Nature and the State Forest Service. These data are used for policy development regarding conservation. The continued existence in their natural environment, which is called in situ conservation, is the preferred strategy for wild species. However, ex situ conservation through the storage of seed samples in gene banks is desired for wild species that are severely endangered under natural conditions. Safeguarding under ex situ conditions will keep the diversity available for potential re-introduction and utilization. For CWR that are included in the Dutch Red List of plant species, CWRnl presents the occurrence in (protected) nature reserves and the presence of seed samples in gene banks, while also more detailed distribution maps for the Netherlands are presented with the Dutch network of protected areas as background.

Occurence in nature reserves

CWRnl presents the occurrence of Red List CWR in areas of the Society for the Preservation of Nature and the State Forest Service, whereby a distinction is made between possible and actual presence. This is due to the fact that a 1km x 1km square may show only partial overlap with these areas, which cannot assure species presence in the nature reserve in case of less accurate observations. It should be noted that species presence involves the period 2000-2015, which means that an observation may be relatively old or more recent. Therefore, actual presence does not provide any guarantee about the current presence of a species in an area

Expected distribution under climate change

Niche modelling, also known as species distribution modelling was used to analyse the expected effects of climate change on the future distribution of species in the Netherlands and Europe as a whole. Through the use of computer models associations are examined between the occurrence of a species at  a certain collecting site and the environmental parameters at the geographic location, such as soil type and climatic conditions as temperature and precipitation. Identified correlations for a species are then used to predict the suitability of locations across a larger area. In addition, predictions are made about the future suitability of geographic locations based on climate change scenarios, such as expected  changes in temperature and precipitation. Comparison of the predictions for current and future suitability provides expectations on future changes in species distribution. The distribution maps that are presented on CWRnl show the expected changes for the year 2070 according to an optimistic and to a pessimistic climate change scenario. These two scenarios are based on a different course of the emission of greenhouse gasses in the next decades. The presented distribution maps are entirely based on the expected suitability of geographic locations as a result of climatic conditions. Thus, other factors that may influence species occurrence, such as dispersal ability, are not taken into account. It should also be noted that predictions depend on the quality of the sampling, which may cause the absence of a species in part of the predicted distribution area (e.g. eastern Europe) in case of lack of well-documented collecting sites from that area.

Links to background information


    CWRnl is an initiative of the Centre for Genetic Resources, the Netherlands (CGN) with the support of Floristic Research the Netherlands (FLORON). The development of CWRnl is part of the Fundamental Research Programme on Sustainable Food and non-Food Production (KB-21-004-001) funded by the Dutch Ministry of Economic Affairs.



    • Dr. R. van Treuren

         Telephone +31 (0)317 480916

         Email robbert.vantreuren@wur.nl

    • Ir. R. Hoekstra

         Telephone +31 (0)317 480912

         Email roel.hoekstra@wur.nl   

    • Dr. Ir. TJL van Hintum

         Telephone +31 (0)317 480913

         Email theo.vanhintum@wur.nl