Assessing the potential risk of spreading the invasive tree species Acer negundo L. with climate change in Europe

Alien tree species are key to improving and enhancing the sustainability of urban green spaces and forest management, but they also pose a threat to global biodiversity in the context of climate change and urbanisation. Using data on the occurrence of the alien tree species Acer negundo L. from the Gbif database, we modelled the availability of potential ecological niches using the MaxEnt method, 19 bioclimatic variables and two additional variables (altitude as an indicator of distribution dependence on relief, human population density) for current conditions, the periods 2041–2060 and 2081–2100 for the territory of Europe. We used two climate scenarios: ssp 126 and ssp 585. We assessed the risks of range expansion for 51 European countries and provided a red list of countries most at risk of invasion by 2100.

Acer negundo is widespread in 31 European countries, with the highest infestation rates in Estonia, Latvia, Slovenia, Serbia, Belarus, the Åland Islands, Romania, Denmark, Georgia, Bosnia and Herzegovina, Bulgaria, Sweden, and France. The Czech Republic and Slovakia have a 16% spread of ssp 585 (2081–2100).

All other countries out of 31 have a forecast of 1-10% of their territory being infected by 2100. In Estonia, Latvia, Slovenia, Serbia, and Belarus, the predicted invasion is 14-75% of the territory in all scenarios and analysed periods, with the most significant expansion of the range in the 15 countries mentioned occurring according to the ssp_126 (2081–100), in which climate change is significantly milder than in ssp_585. Thus, the assessment of invasion risks under the projected climate change scenarios showed that 15 countries have a high risk of invasion. Two countries (Estonia and Latvia) have a 40-75% risk of invasion, with the most significant spread predicted in both scenarios by 2060.

In the Netherlands, Norway, Moldova, Montenegro, Liechtenstein, Andorra, Armenia, Vatican City, the United Kingdom, Greece, Spain, and San Marino, there will be virtually no spread of the species.