National Red Lists in Fennoscandian Conservation: how spatio-temporal dynamics of red-listed species and geographical scale matter for site selection and conservation priorities
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The Red List of threatened species is among the best tools available for management and conservation of species. In this thesis, I study nationally red-listed species at various geographical scales from fine-scale forest areas in Norway, to the region of Fennoscandia. I focus on the use of national Red Lists as a tool for assisting conservation priorities, for identification of important habitats for red-listed species, and for selection of sites for conservation.
For national Red List assessments, most species are assessed at a scale smaller than their distribution range, and the national status is therefore often based on assessment of parts of the total population. This might pose challenges to conservation, as the species can have a different status at broader scales. In the first paper of this thesis, I investigate the effects of geographic scale on nationally red-listed species in Fennoscandia. The national Red Lists of Finland, Norway and Sweden was used to create a dataset of 4830 nationally red-listed forest species from the three countries. From this dataset, a subset called “Candidates for a Fennoscandian Red List” was extracted, and for each country this set of candidates, representing the regional level, was compared with the nationally red-listed species not chosen as candidates. Our results showed that the set of “Candidates” from each country represented a similar composition of organism groups and species of similar forest associations, despite including a lower number of species.
In the second paper, the aim was to investigate if ecological documentation in national Red Lists could be sufficient to characterize general habitat associations and important ecological variables for red-listed species in Fennoscandia. The same Fennoscandian Red List dataset was used, and ecological information extracted for each species and used for analyses. Results showed that criteria documentation in national Red Lists can be used to identify habitat associations and important ecological variables for larger groups of red-listed species, and that the information can be arranged for various selections of species, defined either by geographical scales or by conservation interest. Results showed that the ecological information varied with different selections of species and with scale, highlighting the importance of using appropriate information for the selection or geographic scale of choice. Still, red-listed species is a heterogeneous group, and the results showed a course resolution of the data, not favourable for setting of conservation priorities per se. Even so, the information on red-listed species habitat affiliations and ecology can be valuable as a supplement to national Red Lists. Both these studies on Red Lists in Fennoscandia reveal that combined Red List data can be a source of complementary information that may assist national conservation priorities and assist conservation guidelines for the broaderscale region.
For the second part of the thesis, we scaled down to small-scale forest areas in Norway and investigated red-listed species spatio-temporal dynamics. Red-listed species are often used as target species for conservation sites, but how effectively sites capture red-listed species over time, is less well documented. Loss of effectiveness may be due to at least two different types of dynamics; dynamics caused by compositional changes in Red Lists due to updates, and population dynamics of red-listed species that over time may change both composition and spatial distribution.
In Paper III we investigated the effect of compositional changes in Red Lists for the effectiveness of sites in capturing red-listed species over time. We used occurrence data of red-listed species of bryophytes, macrolichens, polypore fungi and vascular plants from six forest areas in Norway, and four consecutive editions of the Norwegian Red List. We ran a site selection for each area, testing both a hotspot and a complementary site selection strategy. We then estimated the changes in effectiveness of these sites in capturing red-listed species with each new edition of the Red List. Results showed substantial impact of Red List updates on effectiveness of sites in capturing species. The complementary strategy was found to be more effective than the hotspot strategy, but the difference between them decreased over time.
For paper IV, the species occurrence data from two of the six forest areas used in paper III was used, together with data from a re-inventory of these two areas in 2014-15. We investigated spatio-temporal population dynamics of the red-listed species between the two inventories, and found it to be substantial despite an overall similar number of red-listed species. The turnover in species over time was found to alter site selection, as it caused a different set of sites to be selected based on species richness at the two inventories. We also combined the spatio-temporal population dynamics with changes caused by compositional changes in the Red List, and this was found to increase the estimated turnover in species between the two inventories. We therefore argue that both types of dynamics are important to consider when evaluating sites selected for conservation based on occurrences of red-listed species. Although a better understanding of spatio-temporal dynamics of target species has the potential to improve strategies for a more robust site selection, our studies also suggest that a moderate expectancy to the effectiveness and robustness of fine-scale sites based on snapshot occurrences of red-listed species is warranted.
The results from this thesis show that there is still unused potential in national Red Lists in terms of new ways to combine data to withdraw complementary information, and in terms of better understanding of temporal and spatial patterns of red-listed species that influence conservation based on national Red Lists.