Climate change aggravates bog species extinctions in the Black Forest (Germany)

Aim Bogs and transition mires in Central Europe have undergone tremendous changes in the last decades, declining in spatial extent and favourable conservation status. However, species extinctions have been documented only rarely because of a lack of reliable floristic data. Here, we assessed species losses of bog complexes and analysed their potential drivers. Location Black Forest, Germany. Methods We made use of the unique situation that the majority of bogs in the Black Forest (124 sites) had been systematically surveyed from 1972 to 1980 and resurveyed the flora of the same sites between 2017 and 2020. In addition, we included further data from the preceding decades. Results Out of 88 species for which we compiled site occupancy data, two species went extinct in the whole study area and 37 decreased from 1972 to 2020, losing on average 33% of their initial frequency. In contrast, 46 species displayed a positive trend. While decreasing species were characteristic of raised bogs, moorland ponds and base‐rich mires, increasing species were typical of poor mires, fens and wet meadows. Species losses were higher at low elevation, pointing to increasing temperature increase and decreasing precipitation as main drivers of extinction, while habitat area, distance to the nearest site and land use played no significant role. The mean altitude at which extinctions of populations occurred increased with time. Assuming a continuation of the observed negative trends for declining bog species, our models predict the extinction of further ten species by 2045. Main Conclusion Our study highlights the value of systematic and comprehensive past biodiversity surveys to assess biodiversity change. We demonstrated that low‐mountain habitats have already suffered biodiversity loss as a result of climate change. There are only limited management options against rising temperatures and decreasing precipitation.