Crop Wild Relatives - Population inventories in Denmark 2023

In this report we survey a selected list of Crop Wild Relative (CWR) plant species in Denmark. The survey was done at four sites, i.e., Husby, Stråsø, Mols, and Kattrup, which represent a west to east gradient across Denmark, and therefore include different environmental conditions, species pools, and genetic variation.

At each site, plot locations have been generated completely randomized, i.e. including no stratification of vegetation types or environmental condition. Each plot was a circular area with a radius of 15m, where we recorded the presence of CWR species, counted the number of individuals (population density), and assessed in-situ the viability of the population of each CWR species.

Across all four sites, we surveyed a total of 212 plots and found 54 CWR species. To improve the area covered for this inventory, we chose to include occurrence data from other vegetation monitoring thus adding 306 plots (of smaller plot sizes) to the total survey data pool. These additional plots added few species to the total species pool of each area but supported the less intensively surveyed area of Husby for a more comprehensive inventory. The majority of populations were viable, and the four sites represent candidates for future protection of CWR populations. The sites represent large differences in past land-use from a lesser managed coastal dune landscape and heathland to plantations and abandoned crop fields. Therefor we expect that the CWR populations of this inventory might represent a wide range of genetic resources.

This survey found many of the expected species at each site. We therefore conclude that randomized plot selection is successful in capturing the occurrence of CWR, and this simplistic methodology of occurrence and population counts represents a possibility for future monitoring efforts of e.g., population trends of CWR species. However, the monitoring protocol could be further improved by adding a stratification of vegetation and landscape types thus ensuring survey effort of vegetation types that have disproportionate low cover within the total surveyed area.

We propose that the survey methodology used and presented here could be implemented in citizen science efforts and approaches, firstly because of its simplicity in both needed equipment and the field protocol and secondly because it can be adapted to contribute monitoring of not only CWR species but also locally rare or red-listed species.

Observations of CWR species has been uploaded to GBIF: https://www.gbif.org/dataset/095794a9-c50a-4ab1-aa7c-50192569f100