Browsing by Subject "POPULATION TRENDS"

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  • Fraixedas, Sara; Linden, Andreas; Piha, Markus; Cabeza, Mar; Gregory, Richard; Lehikoinen, Aleksi (2020)
    The current loss of biodiversity has been broadly acknowledged as the main cause of ecosystem change. To halt this trend, several international agreements have been made, and various biodiversity metrics have been developed to evaluate whether the targets of these agreements are being met. The process of developing good indicators is not trivial. Indicators should be able to synthesize and communicate our current knowledge, but they also need to meet both scientific and practical criteria. Since it would not be practical to monitor all species, indicators are mainly built on the monitoring of some well-known taxa, such as birds. Here we systematically review the wide spectrum of bird biodiversity indicators (hereafter indicators) available to: i) evaluate recent methodological advances; ii) identify current knowledge gaps jeopardizing indicator interpretation and use in guiding decision-making; and iii) examine challenges in their applicability across different spatial and temporal contexts. We pay particular attention to indicator characteristics such as site and species selection, spatial, seasonal and habitat coverage, and statistical issues in developing indicators and tools to tackle them, to provide specific recommendations for the future construction of indicators. Several methodological advances have recently been made to enhance the process of indicator development, including multiple ways to select sites and species to increase their robustness. However, we found that there are strong spatial, seasonal and habitat biases among the selected indicators. Most of them are from Europe, using mainly census data from the breeding season and typically covering farmland and forest habitats. The major challenges that we detected in their applicability were related to the modelling of the statistical uncertainty associated to the indicator. We recommend the use of quantitative methods in site and species selection procedures whenever possible. Current indicators should be expanded to areas outside Europe and to less studied habitats and should not neglect monitoring work outside the breeding season. Time-series analyses studying temporal trends and using multi-species data should in general account for temporal autocorrelation as well as for phylogenetic correlation. Multi-species hierarchical models are a good alternative for analysing and constructing indicators, but they need to include annual random effects allowing for unexplained annual variation in the average status of the community, i.e. the indicator target. Despite methodological and context-specific differences in the indicators reviewed, most of them seem to highlight the urgent need of devising strategic climate and conservation policies to improve the status and trends of biodiversity.
  • Virkkala, Raimo; Lehikoinen, Aleksi (2017)
    Species richness is predicted to increase in the northern latitudes in the warming climate due to ranges of many southern species expanding northwards. We studied changes in the composition of the whole avifauna and in bird species richness in a period of already warming climate in Finland (in northern Europe) covering 1,100km in south-north gradient across the boreal zone (over 300,000km(2)). We compared bird species richness and species-specific changes (for all 235 bird species that occur in Finland) in range size (number of squares occupied) and range shifts (measured as median of area of occupancy) based on bird atlas studies between 1974-1989 and 2006-2010. In addition, we tested how the habitat preference and migration strategy of species explain species-specific variation in the change of the range size. The study was carried out in 10km squares with similar research intensity in both time periods. The species richness did not change significantly between the two time periods. The composition of the bird fauna, however, changed considerably with 37.0% of species showing an increase and 34.9% a decrease in the numbers of occupied squares, that is, about equal number of species gained and lost their range. Altogether 95.7% of all species (225/235) showed changes either in the numbers of occupied squares or they experienced a range shift (or both). The range size of archipelago birds increased and long-distance migrants declined significantly. Range loss observed in long-distance migrants is in line with the observed population declines of long-distance migrants in the whole Europe. The results show that there is an ongoing considerable species turnover due to climate change and due to land use and other direct human influence. High bird species turnover observed in northern Europe may also affect the functional diversity of species communities.
  • Yrjölä, Rauno A.; Tanskanen, Antti; Sarvanne, Hannu; Vickholm, Jorma; Lehikoinen, Aleksi (2018)
    Urbanization and other human activities can lead to decreasing animal populations in nearby areas. The impact of human activitiesmay vary depending on the characteristics of the areas and region or on the strength of the disturbance. We investigated forest bird population changes in an EU Natura 2000 area during the construction of the new Helsinki Vuosaari Harbour in southern Finland in 2002-2011 as part of an environmental impact assessment. We evaluated whether the changes observed were linked with the harbour construction work by comparing the populations at sites near the development with those corresponding values obtained from national common bird monitoring in southern Finland. Themean population changes of 23 boreal forest bird species that inhabited the Natura 2000 area and southern Finland were significantly and positively correlated, but the population inside the Natura 2000 study area also showed lower mean numbers (a mean decline of 9% occurred over the study period). Our case study emphasizes the importance of intensive monitoring before, during and after work at the construction site and in the surrounding areas to detect actual changes in the populations.
  • Lehikoinen, Aleksi; Johnston, Alison; Massimino, Dario (2021)
    Climate change and human land use are causing changes to species ranges and abundances. However, factors influencing the species-specific speed and direction of changes are not well understood. In addition, intra-specific variation in the responses has rarely been investigated and thus it is not known if the same species show similar population changes in different areas. We compared the rate of changes in range size (since the 1970s) and population abundance (since the 1980s) as well as shifts in mean weighted latitude of range (since the 1970s) and density (since the 1990s) among the same bird species in Finland and Great Britain, two countries that share similar north-south climatic gradients. Similar responses between countries could indicate that climate change is causing parallel changes in species' ranges and abundances in the countries. Furthermore, we tested whether the responses differed between habitat types, which could indicate that local habitat availability and land use may be more important than climate change. Wetland species showed parallel range size change in the wo countries, but no such connection was found in open and forested habitats. Population abundance trends were also parallel in both countries and northern species showed more negative population trends than southern species. The speed of change in species' average latitudes was positively correlated between the two countries when using occurrence data, but negatively correlated when using species density. Species that show similar changes in population sizes in Finland and Great Britain, that are likely caused by large scale population drivers, such as climate change. However, speed of latitudinal shifts in species' densities were not connected between the two countries. These potential differences are likely driven by spatial variation in land use changes and habitat availability.
  • Lehikoinen, Aleksi; Virkkala, Raimo (2016)
    There is increasing evidence that climate change shifts species distributions towards poles and mountain tops. However, most studies are based on presence-absence data, and either abundance or the observation effort has rarely been measured. In addition, hardly any studies have investigated the direction of shifts and factors affecting them. Here, we show using count data on a 1000km south-north gradient in Finland, that between 1970-1989 and 2000-2012, 128 bird species shifted their densities, on average, 37km towards the north north-east. The species-specific directions of the shifts in density were significantly explained by migration behaviour and habitat type. Although the temperatures have also moved on average towards the north north-east (186km), the species-specific directions of the shifts in density and temperature did not correlate due to high variation in density shifts. Findings highlight that climate change is unlikely the only driver of the direction of species density shifts, but species-specific characteristics and human land-use practices are also influencing the direction. Furthermore, the alarming results show that former climatic conditions in the north-west corner of Finland have already moved out of the country. This highlights the need for an international approach in research and conservation actions to mitigate the impacts of climate change.
  • Virkkala, Raimo; Pöyry, Juha; Heikkinen, Risto K.; Lehikoinen, Aleksi; Valkama, Jari (2014)
  • Couet, Josephine; Marjakangas, Emma-Liina; Santangeli, Andrea; Kalas, John Atle; Lindstrom, Ake; Lehikoinen, Aleksi (2022)
    Climate change is pushing species ranges and abundances towards the poles and mountain tops. Although many studies have documented local altitudinal shifts, knowledge of general patterns at a large spatial scale, such as a whole mountain range, is scarce. From a conservation perspective, studying altitudinal shifts in wildlife is relevant because mountain regions often represent biodiversity hotspots and are among the most vulnerable ecosystems. Here, we examine whether altitudinal shifts in birds' abundances have occurred in the Scandinavian mountains over 13 years, and assess whether such shifts are related to species' traits. Using abundance data, we show a clear pattern of uphill shift in the mean altitude of bird abundance across the Scandinavian mountains, with an average speed of 0.9 m per year. Out of 76 species, 7 shifted significantly their abundance uphill. Altitudinal shift was strongly related to species' longevity: short-lived species showed more pronounced uphill shifts in abundance than long-lived species. The observed abundance shifts suggest that uphill shifts are not only driven by a small number of individuals at the range boundaries, but the overall bird abundances are on the move. Overall, the results underscore the wide-ranging impact of climate change and the potential vulnerability of species with slow life histories, as they appear less able to timely respond to rapidly changing climatic conditions.
  • Gamero, Anna; Brotons, Lluis; Brunner, Ariel; Foppen, Ruud; Fornasari, Lorenzo; Gregory, Richard D.; Herrando, Sergi; Horak, David; Jiguet, Frederic; Kmecl, Primoz; Lehikoinen, Aleksi; Lindstrom, Ake; Paquet, Jean-Yves; Reif, Jiri; Sirkiä, Päivi M.; Skorpilova, Jana; van Strien, Arco; Szep, Tibor; Telensky, Tomas; Teufelbauer, Norbert; Trautmann, Sven; van Turnhout, Chris A. M.; Vermouzek, Zdenek; Vikstrom, Thomas; Vorisek, Petr (2017)
    Maximizing the area under biodiversity-related conservation measures is a main target of the European Union (EU) Biodiversity Strategy to 2020. We analyzed whether agrienvironmental schemes (AES) within EU common agricultural policy, special protected areas for birds (SPAs), and Annex I designation within EU Birds Directive had an effect on bird population changes using monitoring data from 39 farmland bird species from 1981 to 2012 at EU scale. Populations of resident and short-distance migrants were larger with increasing SPAs and AES coverage, while Annex I species had higher population growth rates with increasing SPAs, indicating that SPAs may contribute to the protection of mainly target species and species spending most of their life cycle in the EU. Because farmland birds are in decline and the negative relationship of agricultural intensification with their population growth rates was evident during the implementation of AES and SPAs, EU policies seem to generally attenuate the declines of farmland bird populations, but not to reverse them.
  • Mononen, Laura; Auvinen, Ari-Pekka; Packalen, Peter; Virkkala, Raimo; Valbuena, Ruben; Bohlin, Inka; Valkama, Jari; Vihervaara, Petteri (2018)
    Citizens' field observations are increasingly stored in accessible databases, which makes it possible to use them in research. Citizen science (CS) complements the field work that must necessarily be carried out to gain an understanding of any of bird species' ecology. However, CS data holds multiple biases (e.g. presence only data, location error of bird observations, spatial data coverage) that should be paid attention before using the data in scientific research. The use of Airborne Laser Scanning (ALS) enables investigating forest bird species' habitat preferences in detail and over large areas. In this study the breeding time habitat preferences of 25 forest bird species were investigated by coupling CS observations together with nine forest structure parameters that were computed using ALS data and field plot measurements. Habitat preferences were derived by comparing surroundings of presence-only observations against the full landscape. Also, in order to account for bird observation location errors, we analysed several buffering alternatives. The results correspond well with the known ecology of the selected forest bird species. The size of a bird species' territory as well as some behavioural traits affecting detectability (song volume, mobility etc.) seemed to determine which bird species' CS data could be analysed with this approach. Especially the habitats of specialised species with small or medium sized territories differed from the whole forest landscape in the light of several forest structure parameters. Further research is needed to tackle issues related to the behaviour of the observers (e.g. birdwatchers' preference for roads) and characteristics of the observed species (e.g. preference for edge habitats), which may be the reasons for few unexpected results. Our study shows that coupling CS data with ALS yield meaningful results that can be presented with distribution figures easy to understand and, more importantly, that can cover areas larger than what is normally possible by means of purpose-designed research projects. However, the use of CS data requires an understanding of the process of data collection by volunteers. Some of the biases in the data call for further thinking in terms of how the data is collected and analysed.