Effects of climate change and horticultural use on the spread of alien garden plants
The horticulture pathway is one of the most important pathways of alien plant introductions globally. Climate change is predicted to increase the number of species that are able to escape from cultivation. Assessing the relationship between cultivation intensity and the spread of alien ornamental species is important to consider when regulating a species (e.g. import or sale bans) or establishing voluntary codes of conduct or raising consumer awareness: all which will have varying effects on limiting propagule pressure. The potential spread of 15 ornamental plant species was simulated for the 21st century (2010 – 2090) across Europe with statistical modelling. All 15 selected species have not currently naturalised within Europe. Data on the current distribution of the 15 species was extracted from GBIF (Global Biodiversity Information Facility) and for characterizing current climate conditions, six bioclimatic variables from WorldClim were used. Future climate conditions in Europe were represented by three emission scenarios (mild RCP 2.6, intermediate RCP 4.5 and severe RCP 8.5). Habitat suitability of each species was included into the projection models along with six levels of cultivation intensity. Cultivation frequency was included in the models as the size of the area used for planting a species at the European level. The outputs of the models suggest that the spread of potentially invasive garden plants in Europe will not necessarily be dictated by climate change. Although the area of climatic suitability increases, species may not spread fast enough to fill these new areas and currently naturalised areas will become unsuitable for some species. In the models, cultivation frequency had a stronger effect on species spread compared to climate change. Thus, restricting cultivation of invasive plant species can be effective in preventing spread, though this depends on high levels of compliance to keep propagule pressure at a low level.
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Klonner G, Wessely J, Gattringer A, Moser D, Dullinger I, Hulber K, Rumpf S, Block S, Bossdorf O, Carboni M, Conti L, Dawson W, Haeuser E, Hermy M, Münkemüller T, Parepa M, Thuiller W, Van der Veken S, Verheyen K, van Kleunen M, Essl F, Dullinger S (2019) Effects of climate change and horticultural use on the spread of naturalized alien garden plants in Europe. Ecography doi: 10.1111/ecog.04389.