Abstract
Simple SummaryThe Alps are among the most vulnerable ecosystems to climate change, as these modifications take place at a faster pace at higher elevations. Since butterflies are ideal model systems to investigate species responses to climate and habitat changes, we monitored a butterfly community of the Valasco valley in the Maritime Alps (NW Italy) by three sampling events covering a period longer than 40 years. We observed an overall increase in mobile, tolerant and thermophilous species, which eventually might cause an overall loss of community distinctiveness. The variations observed in the butterfly community can be explained by the notable increase in maximum temperatures and the reduction of grasslands, along with the increase of woodlands, supporting the hypothesis that local warming and land-use changes have ultimately affected the butterfly community composition.Our work aims to assess how butterfly communities in the Italian Maritime Alps changed over the past 40 years, in parallel with altitudinal shifts occurring in plant communities. In 2019, we sampled butterflies at 7 grassland sites, between 1300–1900 m, previously investigated in 2009 and 1978, by semi-quantitative linear transects. Fine-scale temperature and precipitation data elaborated by optimal interpolation techniques were used to quantify climate changes. The changes in the vegetation cover and main habitat alterations were assessed by inspection of aerial photographs (1978–2018/1978–2006–2015). The vegetation structure showed a marked decrease of grassland habitats and an increase of woods (1978–2009). Plant physiognomy has remained stable in recent years (2009–2019) with some local exceptions due to geomorphic disturbance. We observed butterfly ‘species substitution’ indicating a general loss in the more specialised and a general gain in more tolerant elements. We did not observe any decrease in species richness, but rather a change in guild compositions, with (i) an overall increased abundance in some widespread and common lowland species and (ii) the disappearance (or strong decrease) of some alpine (high elevation) species, so that ‘resilience’ could be just delusive. Changes in butterfly community composition were consistent with predicted impacts of local warming.
Highlights
Climate studies strongly suggest that atmospheric alteration is already occurring and that changes in atmospheric composition are altering weather and climate processes.Warming of the climate system is unequivocal, as is evident from many observations of an increase in global average surface air temperatures [1]
Closer investigations reveal that during the second half of the 20th century and the beginning of the 21st century the climate of the western Alps has been characterised by an increase in maximum temperatures of up to 2 ◦C, a more modest increase in minimum temperatures and little or no trend in precipitation data, indicating that these changes are happening at a faster pace since the mid-1980s [5,6]
It falls within the Site of Community Importance (SCI: “Argentera” IT1110053) included in the Maritime Alps Natural Park and it is listed among the 32 Italian priority sites for conservation known as “Prime Butterfly Areas” [62]
Summary
Climate studies strongly suggest that atmospheric alteration is already occurring and that changes in atmospheric composition are altering weather and climate processes.Warming of the climate system is unequivocal, as is evident from many observations of an increase in global average surface air temperatures [1]. When observations at lower and higher elevations are compared, alterations are generally enhanced above 500 m [3,4]. Mountain ecosystems provide interesting and valuable models for the early detection of climate change and for investigating its indicators and impact on ecological systems [8,9,10]. Responses vary along with climate change rates, ecological conditions and biogeographical regions [12], global-scale effects of climate change on the biology of many plant and animal species in mountain ecosystems have already been observed [13]. Even if climate might be the main driver at a large spatial scale and its variations are modelled to tackle several general questions [14], smaller-scale factors can alter local species responses [15]
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