Potential alien ranges of European plants will shrink in the future, but less so for already naturalized than for not yet naturalized species

Abstract

Aims:The rapid increase in the number of species that have naturalized beyond their native range is among the most apparent features of the Anthropocene. How alien species will respond to other processes of future global changes is an emerging concern and remains poorly misunderstood. We therefore ask whether naturalized species will respond to climate and land use change differently than those species not yet naturalized anywhere in the world. Location: Global. Methods: We investigated future changes in the potential alien range of vascular plant species endemic to Europe that are either naturalized (n = 272) or not yet naturalized (1,213) outside of Europe. Potential ranges were estimated based on projections of species distribution models using 20 future climate-change scenarios. We mapped current and future global centres of naturalization risk. We also analysed expected changes in latitudinal, elevational and areal extent of species' potential alien ranges. Results: We showed a large potential for more worldwide naturalizations of European plants currently and in the future. The centres of naturalization risk for naturalized and non-naturalized plants largely overlapped, and their location did not change much under projected future climates. Nevertheless, naturalized plants had their potential range shifting poleward over larger distances, whereas the non-naturalized ones had their potential elevational ranges shifting further upslope under the most severe climate change scenarios. As a result, climate and land use changes are predicted to shrink the potential alien range of European plants, but less so for already naturalized than for non-naturalized species. Main conclusions: While currently non-naturalized plants originate frequently from mountain ranges or boreal and Mediterranean biomes in Europe, the naturalized ones usually occur at low elevations, close to human centres of activities. As the latter are expected to increase worldwide, this could explain why the potential alien range of already naturalized plants will shrink less.

Plant invasion in Mediterranean Europe: current hotspots and future scenarios

“…This likely results in only a small and spatially constrained underestimate of the current degree of invasion in some areas, such as eastern Turkey, but may have unknown implications for future predictions (although the global model seems to be more robust to geographic biases; Supporting information). However, we assume that the species selection has only limited confounding effects on our results, as other studies using different selection criteria have found similar patterns (Dawson et al 2017, Bellard et al 2018, Pouteau et al 2021, Schneider et al 2021, Wagner et al 2021. Similarly, new invaders and less common alien species are likely still in a time-lag phase and will need time to naturalise, having marginal effects on our 2050 projections even if environmental and socioeconomic filters changed (Haeuser et al 2018, Wallingford et al 2020.…”

“…A future improvement in this regard could be to develop future predictions of a more comprehensive human footprint variable (Weiss et al 2018), which would replace the human population density by a measure more tightly related to propagule pressure. Second, SDMs generally do not capture the response of alien species to novel climates and nonanalogous climate combinations (Pouteau et al 2021), which likely leads to an underestimation of the effects of phenotypic plasticity, changes in biotic interactions, and evolutionary Page 11 of 14 adaptation in predicting future species distributions (Des Roches et al 2018, Garzón et al 2019). Here we attempted to overcome this limitation by estimating the global niche of species, thereby capturing all known species responses to climate combinations.…”

Invasion risk of the currently cultivated alien flora in southern Africa is predicted to decline under climate change

“…Plants originating from temperate continents have historically been prominent among introduced and naturalized aliens in the region (Omer et al 2021). However, with declines in suitability projected to be steepest for these species (see also Pouteau et al 2021), the composition of southern Africa's naturalized flora is likely to change under warming. These changes, and threats from future invasions more generally, are likely to become more pronounced as cultivators and farmers will use new species that are better adapted to future conditions than species introduced in the past, such as the ones examined in this study.…”

“…Climate‐suitability analyses have emerged as promising tools for predicting the naturalization risk of alien plants (Thuiller et al 2005, Dullinger et al 2017, Haeuser et al 2018, van Kleunen et al 2018, Pouteau et al 2021, Oduor et al 2023); with projections based on future climate scenarios becoming increasingly important for predicting the potential distributions of alien species. In temperate regions as found in Europe and northern America, climate warming is predicted to generally increase the likelihood of biological invasions (Bellard et al 2013, Dullinger et al 2017, Haeuser et al 2018, Oduor et al 2023).…”

“…Most of such studies have been conducted in intensively researched regions (e.g. Europe; Dullinger et al 2017, Haeuser et al 2018, Pouteau et al 2021) or for a specific set of species (e.g. the 100 world's worst invasive species; Bellard et al 2013).…”