The butterfly effect: a farewell from Matthew Oates

Matthew Oates taking visitors on a wildlife walk in the grounds of Osterley Park, Middlesex.

After nearly 30 years as the National Trust’s butterfly expert, Matthew Oates reflects on the meaning of butterflies in his life and ponders what their future might hold.

Whole lives have been dedicated to butterflies – including my own. When I was a schoolboy, I ran around the West Sussex countryside with a net, trying to catch and collect butterflies.

On a sublime morning in mid-May 1968, I first encountered a pearl-bordered fritillary on a woodland path. That was the first butterfly to catch my heart, and I’ve loved them ever since.

Creating safe havens

The National Trust looks after huge tracts of butterfly-rich landscape. This is important as most butterflies need to be able to colonise new areas of habitat as it becomes available, and they die out in patches that deteriorate. They need to wander.

We care for many chalk and limestone grasslands where over half of all the UK’s butterfly species occur. The huge areas on the western Isle of Wight, on Purbeck, Dorset, and along the North Downs escarpment either side of Dorking are examples of intact butterfly landscapes.

It was this natural wealth, and the challenges of butterfly conservation, that lured me into coming to work for the Trust nearly 30 years ago. Much of what has happened with butterflies and their habitats could not have been anticipated then, most notably climate change.

The challenges of a changing climate

Today’s combination of milder winters, early springs and damper summers has radically altered the pace of vegetation growth. Many of the butterflies, bees and other beneficial insects that breed in warm pockets of bare ground are being swamped out by coarse grasses, bracken and bramble.

In places, vegetation is now closing over so fast that some butterflies are no longer able to complete their breeding cycle, from egg to adult, because the cool conditions associated with dense grass growth slow down caterpillar growth and reduce breeding success.

Duke of Burgundy butterflies are faring well on our downs thanks to rangers' conservation efforts
Duke of Burgundy - Hamearis Lucina
Duke of Burgundy butterflies are faring well on our downs thanks to rangers' conservation efforts

It’s not all bad news

The good news is that we know what’s going on. British butterflies are well monitored through the UK Butterfly Monitoring Scheme, established in 1976 and coordinated by the charity Butterfly Conservation.

This means that the health of our butterfly population helps us understand the wider health of our countryside and nature.

Last spring, Butterfly Conservation produced a report for the Trust on how butterflies are doing on our land. The report showed that, overall, the scarcer butterflies are performing better on Trust land than off it.

What happens next?

The challenge for the future of UK butterflies, and for biodiversity in general, is to enable wildlife-rich places to be bigger, better and more joined-up.

The Trust has set itself two targets: to increase populations of rare butterflies on Trust land and to radically increase butterfly numbers on Trust farmland, both by 2025. Of course, butterflies don’t recognise Trust boundaries, so it’s important for us to work with other landowners and partners. We are starting to do this successfully, for example on the Isle of Purbeck, Dorset.

No one has loved a job more than me, but I am retiring to, rather than from, butterflies. I am writing a book on the purple emperor, by far my favourite butterfly and one that could have a rosy future if we can better understand it.

Heath fritillary perched on fern leaf

Holnicote Estate a stronghold for the heath fritillary

Many of the best sites for single rare species of butterfly are cared for by the National Trust. On the Holnicote Estate in Somerset, we’ve halted a decline of the heath fritillary, which now flourishes in some of the heath-covered combes radiating off Dunkery Beacon.

Pearl Bordered Fritillary, male at Oakley Wood, Gloucestershire

Pearl-bordered fritillaries find refuge at Cwm Soden

Cwm Soden, an isolated combe on the Ceredigion coast, is one of the last places in Wales where the pearl-bordered fritillary still thrives. They're recognisable for the two large silver 'pearls' and row of seven outer 'pearls' on the underside hind wing. Flying close to the ground, they stop regularly to feed on spring flowers.