The number of invasive plant species on islands is rising at a global scale. Pennisetum setaceum is a well-known graminoid invader on islands all over the world, among them the island of La Palma, Canary Islands. At the same time this island hosts high percentages of endemic plant species and is of high conservation value. Consequently, there is concern for the potential spreading of P. setaceum on La Palma.
Material and Methods
In-situ occurrences of P. setaceum were recorded from 2010 to 2018 and compiled from databases at a 500 m x 500 m resolution. An ensemble model was used to identify the distribution of the invader on La Palma. Based on this model, impacts of P. setaceum on island ecosystems and protected areas were analysed and risks for total as well as endemic plant species richness were identified.
A total of 37.5% of the terrestrial surface of La Palma has been identified as suitable habitat for P. setaceum. Anthropogenically modified and open landscapes have been shown to be susceptible for invasions of this graminoid. Forests with closed canopies, such as coniferous and broadleaved evergreen forests are likely to be less affected by P. setaceum invasions due to the heliophilous nature of the grass species.
Our results support the prioritization of control measures and management plans for policy makers and conservationists. Furthermore, this study can be applied to other islands where P. setaceum has been recorded as an invasive graminoid.