by Eliane Bornoff and Josephine Tod –

As spring and summer have rolled around at Aigas we have seen the emergence of many species of moths and butterflies. The warmer weather has brought a surge of new moth species into our weekly moth traps, and bright sunny days has seen many a butterfly sunning their wings on the moor. This influx of Lepidoptera has been a learning curve for many of our rangers, providing an opportunity to think about how our changing climate may impact these charismatic invertebrates.

Climate change poses a major threat to species worldwide and the ecosystem services they provide. However, studies carried out over the last 20 years suggest it is not all bad news for our Lepidoptera species. Groups such as our butterflies and moths, which are sensitive to changes in temperature and rainfall, are indicators of these changes we are experiencing in the UK. Evidence suggests that effects of climate change are already impacting our Lepidoptera, both positively and negatively.

Many species are experiencing range expansions. This may be the result of changes to phenology, which is the alteration of an organisms life cycle as a result of environmental variation. With increased temperatures, species start emerging earlier in the year and may therefore produce more generations. This leads to population growth, increased dispersal and colonisation of new areas. Moth species, such as Burnished Brass, have started to adapt to these climatic changes. This has resulted in many individuals producing an extra generation within their yearly life cycle.

A few Lepidoptera species are simply taking advantage of the warming climate and expanding northwards. However, studies are showing that only the stable populations are thriving and expanding their range within the UK. This includes species such the Comma butterfly, which was recorded here at Aigas for the first time last year!

Whilst some species are able to thrive in a warming climate, most are experiencing population declines. Species that are adapted to cooler conditions, such as the Small Pearl Bordered Fritillary, are seeing considerable reductions as a result of temperature change and habitat loss. Warmer climates can decrease availability of food plants and impact specific microclimates that butterflies rely upon. The changing climate also results in increased vegetation growth; creating cooler, shaded conditions at ground level, often impacting butterflies during their larval stage.

Warmer winters and wetter springs have seen species such as the Garden Tiger moth decline by 92% in the last 40 years. Extreme climatic events such as drought can have longer lasting impacts on the following years future Lepidoptera populations. For example, butterfly monitoring in the year following the 1976 drought saw one of the biggest UK population crashes in recent history, with 54 species of butterfly undergoing severe declines that year.

The impacts of climate change on both wildlife and people are starting to be recognised and brought to light across the world. The future of our Lepidoptera is yet another reason for us to make a change and preserve these species for the future.

by Eliane Bornoff and Josephine Tod