Vilka trädarter kan inom 50 år bli invasiva i svenska städer?

Abstract: Our cities are growing more and more, people are moving in and the in the cities congestion is getting bigger (Boverket 2019). Buildings in combination with vehicle traffic and congestion affect air quality (Gustafsson et al. 2014). Research shows that trees, through their ecosystem services, can improve air quality and also affect temperature through these services and counteract the problems with poor air quality and dust particles (Dobbs et al. 2011; Gómez-Baggethun and Barton 2012). Alongside this, climate change is underway and the tree species we today and previously used in urban environments will find it more difficult to cope with the new conditions that come with climate change (Sjöman et al. 2016). It is not only the elevated temperature that causes problems for the city trees. Pests also increase with a warmer climate (Moraal and Jagers Op Akkerhuis 2011), and if you look at, for example, which trees are affected today, among others Aesculus hippocastanum - horse chestnut suffering from Pseudoonas syringae pv. aesculi – bleeding canker and Fraxinus exelsior - ash, afflicted by the ash dieback caused by the fungus Chalara fraxinea (Sjöman and Slagstedt 2015). The solution to this is to use exotic tree species to get a greater species diversity of trees in our Swedish cities so that pests should not spread as quickly as they would have done in a more monocultural population of trees (Sjöman et al. 2012). The problem is that some exotic tree species have become invasive in other countries, creating problems for the native ecosystems. Here in Sweden, this has posed problems, so far with only one species of Ailanthus altissima - god trees (County Administrative Board, Skåne 2019). Several sources warn of other tree species that have become invasive in various places in Europe. This, when Sweden is expected to have as many other places, a warmer climate, which means that the species that are invasive in Europe may also become invasive in Sweden. In the conclusion of this work, the final forecast is presented for which tree species may become invasive in Sweden's three largest cities Stockholm, Göteborg and Malmö with data from, different articles considering invasive species, the species database (artdatabanken) (Strand et al. 2018).