Red-listed plants in semi-natural landscapes

Transcription

1 Red-listed plants in semi-natural landscapes Esgo Kuiper & Anders Bryn Norwegian Forest and Landscape Institute, PO Box 115, Raveien 9, NO-1431 Aas, Norway. Phone: , Abstract Forest regrowth in rural districts of Norway is currently leading to extensive landscape changes. We aim to quantify and understand the future impact of outfield forest regrowth following land-use abandonment on red-listed vascular plant species which are supposedly threatened by regrowth in Norway, i.e. species classified to habitats within the semi-natural landscape. Vascular plant species were defined by the Norwegian Red List and presence data was downloaded from the Norwegian GBIF-node, Artskart. A newly developed spatially explicit model of deforested semi-natural heaths and meadows in Norway was used to evaluate the vulnerability of red-listed plants to future forest regrowth. The results show that some red-listed species may be greatly affected, since they have most of their known populations within the modelled areas of future forest regrowth. The study also revealed that there are many methodological challenges in using museum databases for hypothesis testing. However, the use of such databases was clearly hypothesis generating, giving us many ideas for future studies. Introduction The rural landscapes of Norway have changed through time, and the 20th century marked the beginning of an on-going period of extensive forest regrowth on former outfields and abandoned agricultural land (Bryn & Daugstad 2001). The forest expansion is changing the previously open semi-natural heaths, meadows, and other habitats within the traditional semi-natural landscape of Norway (Fjellstad & Dramstad 1999). Semi-natural landscapes such as the coastal Calluna heaths, boreal heaths, and outfield grasslands are regarded as valuable ecosystems and provide habitats for many threatened species in Norway (Bryn et al. 2010). The threatened species of Norway are defined by the official Red List (Kålås et al. 2010a). This list is valuable for nature management in general, but especially for the needed management prioritizing of rare and highly threatened species. Currently, 369 vascular plant species (27%) of the 1355 evaluated species have a Red List category. Of all vascular plant species, 79 (21.4%) have semi-natural landscapes as one of their main habitats. Thus, a continuation of the forest regrowth in semi-natural landscapes will most probably have a negative effect on the red-listed plant species of Norway (Kålås et al. 2010b). Still, this future process is more or less unknown, since predictive studies of landscape development in Norway are lacking (Hemsing & Bryn in press). However, a newly developed high-resolution GIS model shows that as much as c.15.9% of the total land area in Norway has the potential for forest regrowth after abandoned or reduced human land-use (Bryn et al. in press). In other words, this new model is spatially explicit regarding areas of future forest 68

2 expansion. Also, from 2007 a high number of museum species data became available for digital download from the Norwegian GBIF node (Artskart 2011), including most of the red-listed findings from Norway. In this study we will examine the potential threat of future forest regrowth to the red-listed vascular plant species related to the deforested semi-natural landscapes of outfields in Norway. By doing this we will also determine whether the Norwegian GBIF database Artskart can be used for this kind of research. Material and method Material The study was carried out for the whole of Norway, covering c.323,800 km 2 and extending from 58 N to 71 N and from 5 E to 31 E. The topography rises from sea level to 2469 m a.s.l. and varies greatly in slope, height and age. The latest version of the Norwegian Red List for Species (Kålås et al. 2010a) was used to select vascular plant species (hereafter called species). All species related to the habitat category semi-natural landscape (K) were chosen, including all the Red List categories from Extinct to Near threatened. The registered findings of red-listed species (objects) in Norway were downloaded from Artskart (2011). This map server provides findings from 79 databases, currently containing more than 10,750,000 objects and 19,896 different species, and has recently been updated for red-listed species (9 November 2010). One species had a different name in the Red List (Aristavena setacea) than in Artskart (2011) (Deschampsia setacea). Also, Alchemilla taernaënsis had no objects in Artskart. The potential forest regrowth model has a spatial resolution of 25 x 25 m and covers the whole of Norway (Bryn et al., in press). Clear-cut logging fields, agricultural land, pasture land forests, and all area categories which do not support forest regrowth are not included in the model. Only deforested seminatural outfield landscapes such as coastal and boreal heaths beneath the potential climatic forest limit are included. All other habitats types, e.g. boulder fields, bare rock, mires and peatlands, existing forest, water, alpine regions, built-up areas, roads, and industrial areas were taken from the N50 map series of the Norwegian Mapping Authority, the AR50, or the AR5 map series from the Norwegian Forest and Landscape Institute (Table 1). 69

3 Table 1. Baseline in-put map layer information. All layers were originally in raster format, or converted from vector to raster format. NMA = Norwegian Mapping Authority, NFLI = Norwegian Forest and Landscape Institute. Data layer Data source Updated Raster resolution Data provider Forests, mires, agriculture, N50-series m NMA glaciers, waters, built-up areas, industrial areas, and alpine areas Intensively used agricultural land, agricultural land and grazing fields AR m NFLI Bare rock and boulder fields AR m NFLI Areas of potential forest regrowth according to a new model Bryn et al., in press m NFLI Method First, the downloaded species data from Artskart (2011) were cleaned for unnecessary information such as Institution Name, Basis of Record, and Day Identified. Second, two new columns with categorical data were added: a column for coordinate precision, and a column for year collected. All the objects from before 1950 were excluded from the analyses. Also, coordinates with a registered precision lower than 300 metres were excluded. Some findings did not contain a date or coordinate precision and were also excluded from the calculations. All GIS analyses were run in ArcMap (Version 10.0), including the Spatial Analyst extension. All maps and species coordinates were transformed to UTM zone 33. No map topics were spatially overlapping during the GIS analyses. The following standard GIS functions were frequently used in this study: project (used to transform coordinates to UTM 33), export map (to create a new layer with only the needed information from a specific map), overlay (used to find habitat types corresponding to the objects coordinates), and join (used to find distances from multiple points). After GIS processing the database was exported to Excel. By using a pivot table the results were displayed in graphs. To maintain the overview and save space, only a few random species are presented. Results We downloaded red-listed objects from Artskart (2011). After having excluded old objects (N = 11664) and objects with low precision (N = 20774) which overlapped greatly, we were left with 8086 (28%) objects for further analyses. The following information and analyses are based on the redefined database containing the 8086 objects. Most of the remaining objects have been registered in the 21st century with GPS precision. The species show very different spatial distributions, but most of them are found 70

4 within the nemoral and boreo-nemoral regions of the inner Oslo Fjord. The species also show very different spatial arrangements related to the deforested semi-natural landscapes. Of all registered red-listed species, c.19.2% were distributed within the deforested semi-natural landscapes, whereas c.2.7% were registered within 10 metres of the model. For example, more than 40% of the findings of species such as Gentiana pneumonanthe, Juncus foliosus, and Thalictrum simplex were within the model (± 10 m), whereas for example Campanula cervicaria, Carex pseudocyperus, and Silene nutans were mostly registered outside the model (Figure 1). Figure 1. The spatial relationship of some red-listed species to the deforested semi-natural landscapes of Norway. Distance from model in metres. The habitat distribution of all species reveals that many of the objects were mainly distributed either in deforested semi-natural landscapes (20%), or open areas above the potential climatic forest limit, or in habitats dominated by bare rock or boulder fields (24%) (Figure 2). The latter objects were thus registered outside the areas of potential future forest regrowth following land abandonment. In addition, 32% of the objects were registered in forests, whereas 6% were in mires, bogs, and peatland. Only 10% of the objects were registered within arable land. Altogether 7% of the findings intersected with water, although many of them were close to land. In most cases this was due to lower spatial precision (up to 300 metres). 71

5 1 % 32 % 6 % 24 % 20 % Open area Potential forest Arable land Sea Lake Mire Forest Built-up area 3 % 4 % 10 % Figure 2. The habitat distribution of all red-listed species. Discussion Red-listed species within the deforested semi-natural landscapes Many red-listed species within the semi-natural landscapes of Norway have had decreasing populations and decreasing spatial distributions in recent decades (Kålås et al. 2010a). One of the main negative drivers has been forest regrowth following land-use abandonment (Kålås et al. 2010b). Despite this, the future development of these species has rarely been assessed due to the lack of models of future forest regrowth (Bryn 2008; Hemsing & Bryn in press). However, the access to a newly developed high-resolution model of forest regrowth following land-use abandonment (Bryn et al. in press) has enabled us to study the future vulnerability of all red-listed semi-natural landscape species for the whole of Norway. The presented results document that a number of red-listed species will probably be exposed to future forest regrowth following outfield land-use abandonment. Species such as Leontodon hispidus (66.7% of objects), Comastoma tenellum (58.3%), and Gentiana pneumomanthe (48.1%) all have their main distribution within semi-natural outfield landscapes which have the potential for future forest regrowth. On the other hand, some species were registered outside the model, and are thus threatened by other processes than forest regrowth. However, since more than one-fifth (22%) of the objects were registered within the deforested semi-natural outfield landscapes which are changing rapidly throughout Norway (Bryn 2008; Hemsing & Bryn in press), we conclude that forest regrowth following land-use abandonment constitutes a major future threat to the redlisted semi-natural landscape species of Norway. Challenges and pitfalls when using museum databases for hypothesis testing During the analyses we encountered many challenges and found a number of pitfalls when implementing the museum databases (Newbold 2010). Since landscapes are constantly changing (Farina 2007), old objects had to be excluded from the analyses. The obvious question was then: How old should we allow 72

6 objects to be? Moreover, since some objects had low spatial precision, they also had to be excluded. This raised the question of what level precision is needed. Ultimately, we excluded as much as 72% of all registered objects, leaving only 8086 objects for further analyses. The narrowing of objects can often influence very rare species more than less threatened species and thus result in very few objects of rare species. In general, we believe that the narrowing of objects has increased the validity and reliability of the study, but will reduce opportunities to draw general conclusions regarding species. The data from Artskart (2011) are based on presence-data and do not provide absence-data for species. Also, the objects from the database show findings relating species, but do not provide information about the populations or their local spatial or temporal distribution. In addition, the gathering of species data is most probably biased towards areas with infrastructure, easy access, or many people with interest in biology. Furthermore, uncertainty and resolution challenges relating to the implemented maps and models will have induced potential errors in the study. From the present study we conclude that museum databases can be used with reservations for some general purposes (Newbold 2010). However, our main discovery is that the use of museum databases is highly hypotheses generating, leading to more questions than answers. Acknowledgements This article has been supported by the Research Council of Norway (project number ) and is a part of the scientific project Cultural Landscapes of Tourism and Hospitality (Cultour). References Artskart, (Data download 10 April 2011). Bryn, A., Recent forest limit changes in south-east Norway: Effects of climate change or regrowth after abandoned utilisation? Norwegian Journal of Geography 62, Bryn, A. & Daugstad, K., Summer farming in the subalpine birch forest. In: Wielgolaski, F.E. (ed.), Nordic Mountain Birch Ecosystem. UNESCO Man and Biosphere Series 27. Parthenon Publishing Group, New York, pp Bryn, A., Dramstad, W., Fjellstad, W. & Hofmeister, F., Rule-based GISmodelling for management purposes: A case study from the islands of Froan, Sør- Trøndelag, mid-western Norway. Norwegian Journal of Geography 64, Bryn, A., Dourojeanni, P., Hemsing, L.Ø. & O Donnel, S., in press. A national potential forest model for Norway: A high resolution spatially explicit GIS nullmodel for forest regrowth. Farina, A., Principles and Methods in Landscape Ecology: Towards a Science of Landscape. Springer, Dordrecht. Fjellstad, W. & Dramstad, W., Patterns of change in two contrasting Norwegian agricultural landscapes. Landscape and Urban Planning 45,

7 Hemsing, L.Ø. & Bryn, A., in press. Three methods for modelling potential natural vegetation (PNV) compared: A methodological case study from south-central Norway. Norwegian Journal of Geography. Kålås, J.A., Viken, Å., Henriksen, S. & Skjelseth, S. (Eds.), 2010a. The 2010 Norwegian Red List for Species. Norwegian Biodiversity Information Centre, Trondheim. Kålås, J.A., Henriksen, S., Skjelseth, S. & Viken, Å. (Eds.), 2010b. Environmental Conditions and Impacts for Red List Species. Norwegian Biodiversity Information Centre, Trondheim. Newbold, T., Applications and limitations of museum data for conservation and ecology, with particular attention to species distribution models. Progress in Physical Geography 34,