Abstract
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 1,100 km in south–north gradient across the boreal zone (over 300,000 km2). 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 10 km 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.
Highlights
Global climate change is a major threat to biodiversity (Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012; Pereira et al, 2010), already having a considerable effect on species populations and communities (Chen, Hill, Ohleműller, Roy, & Thomas, 2011; Hickling, Roy, Hill, Fox, & Thomas, 2006; Parmesan, 2006; Stephens et al, 2016)
We studied all bird species observed as breeders to look (1) at possible changes in species richness and composition in order to evaluate whether species richness has already increased in the northern latitudes as predicted by the bioclimatic modeling (Barbet-Massin et al, 2012; Huntley et al, 2007)
The present data are consistent with range shifts caused by climate warming in northern Europe, but there is no increase in bird species richness, at least not at the scale of 10 × 10 km
Summary
Global climate change is a major threat to biodiversity (Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012; Pereira et al, 2010), already having a considerable effect on species populations and communities (Chen, Hill, Ohleműller, Roy, & Thomas, 2011; Hickling, Roy, Hill, Fox, & Thomas, 2006; Parmesan, 2006; Stephens et al, 2016). Barbet-Massin et al (2012) and Huntley, Green, Collingham, and Willis (2007) predicted the changes in bird species richness by 2050 and by the end of 21st century in the whole of Europe based on bioclimatic modeling of each individual species, and Thuiller et al (2014) studied changes in functional diversity of European avian assemblages by 2080. We studied all bird species observed as breeders to look (1) at possible changes in species richness and composition in order to evaluate whether species richness has already increased in the northern latitudes as predicted by the bioclimatic modeling (Barbet-Massin et al, 2012; Huntley et al, 2007). Pöyry, Heikkinen, Lehikoinen, and Valkama (2014) showed that ranges of northern bird species had already changed in the same direction as the predictions of species- climate change models. Have resident versus migratory bird species gained or lost ranges and are there any patterns between different habitats with certain habitat including more species with expanding ranges and another including more species with contracting ranges?
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