Provide shady spots to protect butterflies from climate change, say scientists

https://www.eurekalert.org/pub_releases/2020-09/uoc-pss092220.php

News Release 24-Sep-2020
University of Cambridge

Researchers have discovered significant variations in the ability of different UK butterfly species to maintain a suitable body temperature. Species that rely most on finding a suitably shady location to keep cool are at the greatest risk of population decline. The results predict how climate change might impact butterfly communities, and will inform conservation strategies to protect them.

•••••

The results, published today in the Journal of Animal Ecology, show that larger and paler butterflies including the Large White (Pieris brassicae) and Brimstone (Gonepteryx rhamni) are best able to buffer themselves against environmental temperature swings. They angle their large, reflective wings in relation to the sun, and use them to direct the sun's heat either away from, or onto their bodies. These species have either stable or growing populations.

More colourful larger species such as the Peacock (Aglais io) and Red Admiral (Vanessa atalanta) have greater difficulty controlling their body temperature, but even they are better than their smaller relatives like the Small Heath (Coenonympha pamphilus).

The study found that some butterfly species rely on finding a spot at a specific temperature within a landscape - termed a 'microclimate' - to control their body temperature. Air temperatures vary on a fine scale: a shaded patch of ground is cooler than one in full sun, for example. These 'thermal specialists', including Brown Argus (Aricia agestis) and Small Copper (Lycaena phlaeas), have suffered larger population declines over the last 40 years.

All butterflies are ectotherms: they can't generate their own body heat. The populations of two thirds of UK butterfly species are in decline: habitat loss and fragmentation, and more monotonous landscapes have removed many of the microclimates butterflies need to survive. Climate change is compounding the problem by causing more extreme weather events and greater fluctuations in temperature.

Insects, including butterflies, pollinate around 85% of our food crops - providing a vital service worth billions of pounds globally. Protecting a diverse range of species will provide long-term resilience: if numbers of one species fall there are others to fill the gaps. Insects are also an important food source for many other species, including birds. 

•••••