DOI: 10.5061/dryad.mw6m905vj
title: Table S5: Occupancy change observations in bog species in the Black Forest (Germany) across all sites from 1972-2019

description: Aim: Bogs and transition mires in Central Europe have undergone tremendous
 changes in the last decades, declining in spatial extent and favorable
 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 analyzed 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.
description: <b>Study site. </b>The study area comprised the
 southern part of the Black Forest, an area of about 500
 km<sup>2</sup> (Figure 1). While the study area only covers
 about one third of all bog sites in the Black Forest, the vast majority of
 rare and regionally typical bog species occurred here. Within the study
 region, elevation ranges from approximately 300 m above sea level in the
 Rhine valley in the south to almost 1,500 m above sea level at the summit
 of the Feldberg in the northwest. This elevational gradient offers the
 opportunity to relate possible changes to climatic drivers, in particular
 to precipitation and temperature. The majority of the
 bog complexes is located in forested valleys and on slopes and not used
 for forestry, except for some marginal areas. Some other bog complexes are
 found on sloping valley floors or plateaus that are used for low-intensity
 agriculture. Almost all bog complexes have been affected by drainage
 ditches, which in most cases were created more than 50 years ago and are
 no longer maintained today. To our knowledge, in the past few decades, new
 drainage ditches have only been established in exceptional cases,
 affecting only small areas (von Sengbusch, 2015). As we were not able to
 collect water level data at all sites and drainage conditions did not
 change in almost all sites, we did not include them in the subsequent
 analyses. <b>Data compilation. </b>In
 total, species inventories of typical vascular plant species of bog
 complexes were compiled for 124 bogs with presence/absence. In particular,
 106 bogs were included that had been surveyed by Barbara Dierßen and Klaus
 Dierßen four to five decades ago in the study area (B. Dierßen &
 Dierßen, 1984). Locations of all sites of bog complexes (as listed in
 Appendix Table S1 in Supporting Information) were digitized as
 polygons. In addition to the bog sites surveyed by
 Dierßen & Dierßen themselves, B. Dierßen & K. Dierßen
 (1984) included a species list from one site from literature and eight
 further sites were included that had been recorded at the same time by
 Schuhwerk (1988). These records were made between 1972 and 1980 (Appendix
 Table S2 in Supporting Information). Further nine bog complexes were
 included that were only surveyed in the 1980s and 1990s. There are further
 bog sites inside the study region, which however, are either very small or
 mostly very species-poor, and thus, not considered in our study. From 2017
 to 2020, the first author resurveyed 123 sites, most of them twice. To
 complete these census species lists, we added occurrence data from habitat
 mapping campaigns carried out in these four years. For the period between
 1980 and 2017, we collected occurrence data from habitat mapping
 campaigns, expert reports for nature conservation value of some of the
 sites, the species protection programme of the federal state of
 Baden-Württemberg and unpublished records based on the expertises of local
 biologists (Appendix Table S2 in Supporting Information).
 Out of the species lists of all surveys, we selected 109 vascular
 plant species. On the one hand, the selected species can be considered
 typical of raised and quaking bogs, as well as mires and, in particular,
 transition mires. On the other hand, species were included that are common
 in peat woodlands, wet meadows and fens. Species from this second group
 are usually absent in undisturbed and intact bogs and mires, but are
 widespread in degraded stands. These species were included to detect
 effects of drainage and eutrophication (see species` habitat preferences
 in Appendix Table S3 in Supporting Information). We then checked for
 species with insufficient number of observations. From the initial pool of
 109 target species, we removed those without repeated records as well as
 those that were not recorded by the majority of the authors or whose
 identification by some recorders was questionable. For example, we
 excluded <i>Scutellaria minor</i> because the species has
 never been recorded by B. Dierßen & K. Dierßen (1984) although its
 presence had been documented in bog complexes at low elevation since at
 least 1961 (Sebald, O. et al., 1996). Species taxonomy follows Rothmaler
 (Jäger, 2017). We aggregated <i>Dactylorhiza traunsteineri</i>
 and <i>D. majalis</i> as <i>D. majalis</i> agg.
 because these species were not distinguished in all past surveys. Finally,
 88 species remained, with a total of 5076 occupancy change observations
 across all sites (for the data see Appendix Table S5 in Supporting
 Information). Across all sites, the mean number of occupancy change
 observations per species (that is whether a species was newly recorded at
 a site or no longer occurred) was 57.7 (min 1, max 118). Overall, the
 final database consisted of 814 species lists and a total of 72,268
 presence/absence (p/a observations, with on average 583 species records
 per site and 6.5 (min 1, max 16) repeated records per species per site.
 The lists vary in completeness. An exception is the most recent species
 inventory for the period 2017 to 2020, which can be considered nearly
 complete. The assessment of extinction events at the scale of hectares
 generally involves the difficulty that absences of every species have to
 be examined across the total area of every bog complex. Thus, even with
 the extensive data on which our study is based, past extinction events
 always pose a risk that species may have been overlooked (Beck et al.,
 2018). Thus, it is difficult to assess when exactly species that were
 absent in our last systematic survey from 2017 to 2020 went extinct. For
 example, <i>Carex frigida</i> went extinct at site 160
 (Quellgebiet Sägenbach) between 1973, when the species was recorded by B.
 Dierßen & Dierßen (1984) and 2018. Within this period, the
 extinction could have happened any time because we had no further survey
 data.
description: Site_ID: number used in the map in Figure 1 and in Appendix Table
 S1; Species: Taxon name; Year_first_obs: Year when the species was first
 observed at this site; Year_last_obs: Year when the species was last
 observed at this site; Occ_change: indicates whether a species went
 extinct (-1), remained occurring (0) or newly occurred (+1) at this site;
 Year_subsequent_survey: Year  of the subsequent survey in which the
 species was no longer detected at the site; Ext_event: refers to declining
 species and shows the extinction event (-1) that corresponds to the year
 of the subsequent survey.