The great puzzle has been why some species of moth and butterflies have been increasing and spreading, whilst others have declined in the last 40 years. Now we know that most of the differences arise because each species responds in a different way to the climate. Some like it hot, some like it cold. Some like it hot in winter but not in summer. Some like it wet in spring, others dry in the autumn.
It has been repeatedly shown that organismal response to climate change varies greatly from species to species. Furthermore, this variability has been regarded as very complex due to the number of biotic interactions. This in turn has led to concerns that predictions of responses are inherently uncertain.
Variation among species is attributed to differing sensitivity to climate change, and also because species vary in how much the climate has changed for them (their ‘exposure’). Sensitivity is a measure of how much species’ numbers change as a result of year-to-year changes in the weather because each species is sensitive to different aspects of the climate, such as winter temperature or summer rainfall.
Researchers from the UK have now analysed how the abundance and distribution of 155 species of British butterflies and moths have changed since the 1970s. Using data collected by thousands of volunteers through ‘citizen science’ schemes, responses to recent climate change were seen to vary greatly from species to species.
It turns out that these 155 different species of butterflies and moth have almost 155 different ‘opinions’ on how much the climate has changed, and whether it has got better or worse. Climate change is causing massive alterations to our wildlife.
Results show that species such as the treble brown spot moth (Idaea trigeminata) and the speckled wood butterfly (Pararge aegeria) which are sensitive to climate, and for which the climate has improved the most, have experienced the greatest increases in their distribution size and abundance. Conversely, other species, such as the grizzled skipper butterfly (Pyrgus malvae), the September thorn moth (Ennomos erosaria) and the mouse moth (Amphipyra tragopoginis), have experienced deteriorating climates resulting in declines in abundance and distribution size.
Species are sensitive to different aspects of the climate, which results in species being exposed to different levels of climate change. Nearly two-thirds of the changes in abundance can be explained by these species-specific differences. This means that their responses to climate change may be more predictable than previously recognised.