Are butterflies our local ‘canary in the coal-mine’?

Invertebrates (or more specifically insects) are a widely studied group of animals throughout the globe, with more studies than you can ‘poke a stick at’. These studies range from understanding more about individual species or populations in a given area through to particular guilds of insects or landscape/continental scale changes, such as in pollinator declines. All of this research is aiming to give other researchers and perhaps more importantly land managers a view of how things are faring.

Photo of a Marbled Xenica, a butterfly species distributed across southern Australia.

The UK and northern hemisphere scientists seem to have started monitoring many years before southern hemisphere countries, so our northern counterparts have much data to share. The interesting aspect of this though is that people all over the globe seem to be saying the same thing: “We need to change our practices otherwise things are going to get grim” – even though they already are!!

‘Vertebrate insectivores’ such as birds are also often monitored in studies as a proxy for how healthy an environment or landscape is. Many of these studies are telling us that declines are happening everywhere. Recent wildfires and extensive droughts are also adding to this declining trend.

A dear friend (Chris Wilson) who came to Australia in 2000 introduced me to monitoring insects, especially butterflies, and he and I set up the Penambol Conservation Park Butterfly Walk – which still runs today – 20 years on. Long term monitoring datasets are a key management tool and we simply don’t have enough of them in Australia to be able to inform decisions about our amazing wildlife and biodiversity and whether our restoration actions are working and/or if populations of our wildlife species are self-sustaining.

Butterflies can be used as habitat quality indicators whereby the abundance in a particular area can be a surrogate for condition reporting in a similar way frogs are for wetlands or birds are in a general sense of how healthy an environment is. After nearly 20 years now I believe insects are telling us something about our environment, particularly as potential indicators of climate change, which for us (south-eastern South Australia / south-western Victoria) includes the impacts of drought; for others it might be impacts of floods or wildfires.

I have talked about the Penambol Conservation Park Butterfly Walk before – mentioning how I walk it once a week for 20-25 weeks of the year identifying and counting all of the butterflies seen. The walk takes about 20 minutes to complete … so not a daunting task and most of the time some well needed exercise after a busy period in the office.

The data I have gathered could be telling us something interesting about the health of butterfly populations in that district, especially when looking closely at the Marbled Xenica. Here are some initial thoughts:

The common and widespread species ‘Marbled Xenica’ (Geitoneura klugii) displays a very consistent first emergence (late December to early January). Late emergence in 2006/07 and 2019/20 are possibly very closely linked to drought, as explored in my previous post.

Marbled Xenica showing a consistent start to its flight period each year except for the drought years (2006-07 & 2019-20).

When considering the abundance of Marbled Xenica over the same period, there was some recovery following the severe 2006-2007 drought, as seen in the chart below. But as you can see since 2017 the abundance measured has remained quite low leading into the drought from 2019. Will the population be able to recover again?

Abundance of Marbled Xenica showing sharp decline following sever drought years.

One species has completely disappeared – Orange Ochre (Trapezites eliena). This species was observed at the beginning of the monitoring (in 2000) and recorded sporadically during each year; however, it was last seen in December 2011.

Orange Ochre – almost 10 years since it was last seen at Penambol Conservation Park.

And finally, the Splendid Ochre (Trapezites symmomus). This enigmatic species is emerging earlier in the summer than it was in the early 2000’s.

Splendid Ochre showing an obvious trend towards flying earlier since monitoring began.

Splendid Ochre.

So, monitoring is critical to track changes in our landscape and to help inform decisions about how to best manage land and changing situations; making us better custodians in the long-term! Because even in my short life – ‘things are a changin’!

If you’d like to look into this subject a little more I encourage you to watch this YouTube video of a talk by Akito Kawahara speaking at an Entomology Conference held in St Louis (USA) late last year. Akito offers guidance towards our future thinking and actions, especially in the education space, to transfer this scientific knowledge and to gain greater momentum towards curriculum-based interactive outdoor learning activities from K- Year 12; thus informing and empowering our young generation.

Bryan Haywood
Bryan Haywood