The Global Naturalized Alien Flora database: patterns and drivers of plant invasions

Humans have intentionally and unintentionally introduced many species from their native regions into regions where they did not previously occur. Some of these species have become naturalized, and some of those have become invasive. However, only in the last couple of years, the global extent and patterns of such biological invasions have started to emerge. This has been possible through large- scale collaborative initiatives such as the Global Naturalized Alien Flora (GloNAF) database, funded by the DFG and FWF. The GloNAF database currently includes entries of 13,977 alien vascular plant species in 876 non-overlapping regions. In this follow-up proposal, we want (1) to continue updating and expanding GloNAF, (2) to assess and explain geographic and taxonomic patterns in numbers of naturalized species, (3) to test whether different attributes and economic uses of species are related to invasion success, along different dimensions of invasion success and across time, and (4) to predict future invasions based on different scenarios of global investments, bilateral trade and global environmental change.

This project focused on understanding patterns and drivers of naturalized alien floras worldwide. A main task was the extension and publication of the GloNAF database so that it is freely accessible for everyone to use. Also, we tried to disentangle which socio-economic and evolutionary factors shape the distribution of alien plants globally and across continents and how the number of alien plants have change over time. We could show, that especially if a species was introduced to a new region for economic purposes (e.g., for food or medicinal purposes) its possibility to become established in that new regions significantly increases. Besides this cultivation history, the level of human development in a specific region and how similar the climates of the native and alien range of the species are influences how likely it is for the species to establish. But also, characteristics specific to the introduced species can increase its likelihood of establishing in the new region. For example, plant families with high rates of evolution of new species are more successful in naturalizing but also the life-history of species can be crucial, e.g., if a species has a short generation time and low environmental requirements. When looking back in time, the development of a global trading network because of the European exploration in the late 15th century has strongly shaped how species were and are now moved across the globe. Europe was hence a major driver of redistributing species across the globe, however this influence has changed following the disintegration of the European empires and the restructuring of the global economy and trade. By understanding these historic trends, we projected how alien species numbers and impacts are likely going to change in the future and found that by 2050 we expect an increase of alien species by 36% if current trends prevail. Also, the negative impacts of alien species on biodiversity will likely increase until 2050 across all different regions of the globe. Overall, the project provided crucial new insights into what shapes the distribution of naturalized alien plants worldwide.