Relative impact of native and non‐native plants on endangered species in a major European City

Abstract International policies increasingly call on decision‐makers to enhance urban biodiversity. While cities can support considerable biological richness—including rare and endangered species—the persistence of plant populations in urban habitats is often at risk. Identifying and prioritizing threats to endangered plants is essential for guiding effective conservation strategies. We analysed a unique dataset derived from expert assessments of threats to 1231 populations of 201 endangered species within Berlin's Flora Protection Programme. Threats were categorized and their relative importance quantified at both population and species levels, and across habitat types. Biotic threats were most prevalent—affecting 63% of populations and 78% of species, followed by threats related to agriculture, nutrient inputs, urban development and recreation. Among biotic threats, succession and expansive plant species were similarly important, each affecting 23%–25% of populations, followed by tree and shrub plantings (11.5%). Native species (primarily Calamagrostis epigejos and Phragmites australis ) threatened 16% of populations while non‐native species (mainly Solidago taxa and Prunus serotina ) affected 15.2%. The relevance of non‐native threats varied across habitat types, with woodlands hosting the largest number of affected populations. Despite Berlin's status as an invasion hotspot, non‐native species represented a comparatively minor threat relative to other biotic drivers, agriculture and nutrient inputs—consistently across major habitat types. Notably, no EU‐listed Invasive Alien Species were identified as threats to the target taxa—including the widespread Ailanthus altissima . Synthesis and applications. This first city‐wide assessment of threats to multiple populations of endangered plant species provides a foundation for targeted threat management in urban contexts. Maintaining habitat quality and optimizing land use will be most effective in protecting endangered species from competitive pressures. While existing non‐native threats should be addressed, their limited role suggests that urban conservation efforts should prioritize more pressing drivers of decline. In Berlin, many endangered native species likely co‐exist with non‐native species at broader spatial scales. Future studies should move beyond isolated assessment of invasion risks, compare the relative importance of different threats and apply this framework across cities in diverse biogeographical and socio‐economic settings.