Browsing by Subject "extinction risk"
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(2019)Not much attention is paid on the conservation of invertebrates despite their importance to the ecosystems in general and their benefits and ecosystem services to us, humans. This study is part of a project aiming to start the Sampled Red List Index (SRLI) for spiders. The IUCN Red List Index (RLI) is used for measuring the overall extinction risk of groups of species and the sampled approach is a way to evaluate the trajectory towards extinction of megadiverse groups without the need to assess every species of the whole group of interest. A random sample of 200 spider species were selected from the global checklist and assessed according to IUCN Red List Categories and Criteria. Given the availability of data, I was able to calculate the extent of occurrence and area of occupancy for 80 species, of which 70 species had an EOO above 20000 km² and 75 species an AOO above 2000 km², the thresholds below which species can be considered threatened. The trends in EOO and AOO were assumed to be stable for most species (49 species) given the inexistence of monitoring data for any taxon. Evidence of decline was found for only 10 species, usually inferred from habitat loss. Habitat data was collected for 118 species. The most common habitat type was forest (73 species), followed by grasslands (24 species) and artificial habitats (22 species). For 44 species the habitat trend was inferred to be stable, only declining, according to available knowledge, for 14 species and increasing for one species. For the remaining 141 species the habitat trend could not be inferred and was thus assumed to be unknown. The most commonly mentioned threat types were agriculture (11 species), fires (7 species) and logging (6 species). For 39 species there were no known threats and for the rest of the 132 species the threats were unknown. Conservation actions in place were observed for 104 species, most commonly site and area protection (100 species) and resource and habitat protection (88 species). Conservation actions such as education and awareness (8 species), resource and habitat protection (7 species) and site and area management (6 species) were to take into consideration. All the 200 species were estimated to be in need of further basic research especially on threats (143 species and distribution (140 species), but also on life history and ecology (135 species). Due to several knowledge shortfalls, including the Wallacean (distribution of species), Prestonian (population trends) and Hutchinsonian (response to environmental change), no threat category could be reached for the vast majority of the species. The results show that an IUCN category could be reached for only 59 species, of which 55 were assessed as Least Concern and a threatened category was reached for only 4 species (t as Critically Endangered and one as Vulnerable). The baseline SRLI at this first point in time was 0.95 (in a 0-1 scale, where 0 means all species are extinct and 1 for all species are Least Concern). We hypothesize however that among the 141 Data Deficient species there should be a higher proportion of threatened species than among the 59 evaluated. This would be due to two reasons. First, the scarcity of information on many species might in part be due to their rarity. Second, widespread species were often the only for which an assessment could be reached, creating a bias in the dataset towards a large base SRLI value. The strategy currently imposed by IUCN is therefore clearly inadequate for taxa with scarce information, which represent the vast majority of species. I propose the future use of a different, non-random, approach to the selection of species in the SRLI and its adoption for other taxa which represent in fact most extant and threatened species.
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(2018)The Red List Index (RLI) has widely been recognized as a useful tool in keeping track of extinction risk trends of large taxa. The RLI is an index based on IUCN’s threat categories. Functional diversity (FD) is a way of measuring biodiversity that describes species´ traits that are linked to species´ ecological roles. In this work I have mapped the spatial distribution of the RLI and functional diversity for Finnish vascular plants. I first produced species distribution models (SDMs) for all 1194 species of vascular plants in the Finnish Red List 2010 based on records from the Kastikka and Hertta databases and environmental data. A functional tree incorporating 971 of those species was calculated using seven functional traits. The traits that I used were life form, maximum plant height, seed mass, seedbank longevity, life span, specific leaf area (SLA), and leaf dry matter content (LDMC). The trait data was gained from the databases Leda and TRY. Based on the SDMs, the functional tree, and the Finnish Red List, taxonomic and functional diversity and RLI were mapped for the whole of Finland using 10 x 10 km cells. This was the first time FD and RLI were mapped for vascular plant species across Finland. Null models were used to compare observed values with the ones expected if species (and consequently traits) distributions were random accross the country. Taxonomic diversity (TD) was higher than expected in southern Finland and lowest in northern Finland, suggesting a strong latitudinal gradient. TD correlated with the same environmental variables as FD. Thus, it is likely that both TD and FD are dirven by the same environmental variables. FD was higher than expected in southern and western Finland and lower in the northern and eastern parts of the country. A strong environmental filtering in the north might cause low FD by limiting species´ distributions within many clades and favouring species with similar traits that allow them to survive in extreme conditions. In southern Finland, competitive exclusion might limit the co-existence of species with similar traits, thus increasing trait divergence. The RLI values were lowest in the Åland islands, along the southern coast, in a few sites in eastern Finland (e.g. Koli and Kuusamo areas), around Kemi and the Gulf of Bothnia and in Kilpisjärvi. Thus, these sites have high concentrations of threatened species. The low RLI sites correspond well with areas with either limestone or dolomite deposits, which explains why many of these areas are floristically unique and present high concentrations of threatened species. In addition, many of the sites with low RLI are geographical extreme areas in Finland, corresponding to the distribution limits of many species. The RLI was high in Ostrobothnia and in large parts of Lapland. In Ostrobothnia, centuries of forest management and a homogenous bedrock and topography have resulted in a vascular plant community based mostly on common species. It is possible, that regional extinctions have happened in Ostrobothnia already before red listing measures began, thus explaining the high RLI values today. On sites with more variety among habitats and bedrock, the RLI values were significantly lower than in the rest of Lapland, suggesting that the high RLI values for parts of Lapland are due to homogeneous plant communities in the northern boreal forests that host only few threatened species. The spatial distribution of the RLI and functional diversity for vascular plants in Finland were mapped for the first time. A strong latitudinal gradient was found for TD and FD. Low RLI values were found on calcareous soils and on geographic extremes in Finland. To track possible changes in the RLI it would be crucial to remap the RLI in 2019 when the next Finnish Red List is published. A comparision between this work and the remapping based on the 2019 assessment would track changes in the extinction risk across Finland. The current limitation with RLI is that it only considers taxonomic diversity. However, in future work it is possible to incorporate the functional tree used in this thesis into RLI to calculate a functionally weighted RLI.
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