Climate-driven changes in pollinator assemblages during the last 60 years in an Arctic mountain region in Northern Scandinavia

Abstract

Climate change is occurring more rapidly in the Arctic than elsewhere, and is predicted to have a large impact on biodiversity, since entire cold-adapted ecosystems are likely to disappear. Here, we highlight changes in the insect species richness and community composition of wild bees, butterflies and moths over 60 years in an area situated above the tree limit (Padjelanta National Park) in northern Sweden. Although there were changes in habitat availability, indicated by a significant decrease in the area of a glacier (from 22 km 2 in 1898 to 7.5 km 2 in 2009), and an increase in the area of birch forest in the National Park, we nevertheless found relatively moderate changes in the insect communities. Indeed, the observed number of species increased from 52 in 1944 to 64 in 2008. Remarkably, the mean number of butterflies and moths per site, but not wild bee species, increased significantly. Among the species that were recorded in both periods, the average altitude of 17 species had shifted downhill, 12 shifted uphill, and the altitude of the remaining 17 had not changed. While alterations in community composition were greater at the highest altitudes, changes in the insect community were smaller than expected, indeed much smaller than those reported from agricultural landscapes in North-West Europe. Interestingly, our results suggest that lower alpine altitudes (600-800 m a.s.l.) have become colonized by southern species, but also that high alpine areas (above 1,000 m a.s.l.) have recently become colonized by high alpine species previously absent from these sites, likely as a result of increasing habitat availability. We conclude that wild bee, butterfly, and moth communities in Arctic areas in northern Sweden are in flux, as a result of climate change and suggest that increased attention must be given to conservation planning in cold areas. In addition, we propose that monitoring programs should be established, because more pronounced climate-driven changes can be expected in the future.

Assessing abundance patterns of specialized bog butterflies over 12 years in northern Wisconsin USA

“…Warren et al (2001) noted that the ranges of many British butterfly species appear limited by factors other than climate, since they are not occupying all areas that are climatically suitable. Unexpected outcomes such as downhill expansion of some high arctic butterflies in a Swedish arctic alpine national park may result from the complexity of seasonal variation in both temperature and precipitation (Franzén and Ö ckinger 2012). The large variation in annual abundance of bog butterflies in this study, and uncertainty about longer-term effects of climate, highlight the value of longer monitoring periods than in our study (Thomas et al 2002).…”

Complex Messages in Long-Term Monitoring of Regal Fritillary (Speyeria idalia) (Lepidoptera: Nymphalidae) in the State of Wisconsin, USA, 1988–2015

“…Since Wisconsin is at the northern edge of the species’ range, this may be a possible consequence of climate change. Many butterfly species have been documented to increase in abundance in their northern range, and expand their range, in recent decades in association with warming climate [61,62,63,64,65,66]. …”

Grass-skipper (Hesperiinae) trends in midwestern USA grasslands during 1988–2013

“…This suggests that other factors besides climate, such as habitat quality and landscape conditions, contribute to these trends, both in that study and in ours (Warren et al 2001). Likewise, some field studies and models have produced unexpected results, such as alpine species expanding downhill (Franzén and Ö ckinger 2012), cooler areas increasing in butterfly richness more so than warmer places (Isaac et al 2011), and species from both the warm and cold ends of their range declining more compared to corerange species (Filz et al 2013). Since non-negative abundance trends facilitate butterfly species' range adjustments in response to climate change (Mair et al 2014), the many negative population trends in this study may contribute to these unexpected patterns relative to southern or northern ranges.…”