Arnica montana is characteristic of spikenard meadows (Nardo-Galion). This type of biotope is highly threatened throughout Europe. The main causes of the decline are changes in agricultural practices, in particular the fertilization and liming of meadows (Colling 2005). As Arnica montana is a long-lived species, it is able to survive in habitats that differ from its native habitat, particularly in abandoned grasslands if they are not fertilized. However, lack of management (extensive grazing and late mowing) prevents the survival of young seedlings, and the species is restricted to vegetative reproduction by rhizomes. Arnica montana populations in Luxembourg are doomed to disappear in the next ten years if population restoration measures are not urgently implemented.
The strategic objective is to significantly increase the size of current Arnica montana populations. The current very small populations are not viable because the species has a system of genetic incompatibility at the level of sexual reproduction. We estimate the minimum number of Arnica montana individuals per population to be 500, in order to have a viable population in the medium term. All current populations are considerably smaller. The reintroduction of Arnica montana to historical sites should also be considered. Arnica montana does not have a seed bank, and the reappearance of the species in a favorable habitat is highly unlikely, given the low dispersal capacity of the seeds, which is limited to a few meters. The strategic objective is to restore and create 10 local populations of Arnica montana with numbers in excess of 500 individuals. It should be noted that in this species, the number of individuals differs greatly from the number of rosettes, which can be much higher due to the fact that the plant reproduces vegetatively using rhizomes.
