Generally speaking, insects are in big trouble. The 2019 report Insect Declines and Why They Matter drew together evidence showing that insects may have declined by up to 50% since 1970, and data collected by the UK Butterfly Monitoring Scheme (UKBMS) in 2020 showed that almost a third of UK butterfly species are in long term decline. This deterioration in insect abundance is thought to be largely due to habitat loss and increased use of pesticides and herbicides.
But thankfully it seems there's a glimmer of hope as London’s butterflies might actually be considered something of a success story.
In 1987 The London Natural History Society published The Butterflies of the London Area by Colin W Plant which was the result of years of research and monitoring of butterfly species across the capital but most specifically 1980-86. At this point there were 22 generalist species present in inner London and it was thought this number had been stable for around 100 years:
• Small, Essex & Large Skippers
• Brimstone, Orange-tip, Large, Small & Green-veined Whites, Clouded Yellow
• Small Copper, Common Blue, Holly Blue
• Red Admiral, Painted Lady, Comma, Small Tortoiseshell, Peacock, Speckled Wood, Wall, Gatekeeper, Meadow Brown, Small Heath
UKBMS data from 2019/20 estimates that the city is now home to ~30 species with the addition of the following species:
• Brown Argus, Small Blue, Brown, Purple and Green and White-letter Hairstreaks
• Purple Emperor, Marbled White, Ringlet, Silver-washed Fritillary
The Wall is the only butterfly species to be found in London during the 80s that can longer be seen. Whilst researching for the 33 Butterflies challenge, I was surprised at how abundant the London records were for the Wall but it has suffered severe declines in recent decades and is now mainly found in coastal regions.
White-letter and Purple Hairstreaks are canopy species with the former favouring Elm and the latter Oak. Both species have shown significant increases in abundance in recent years with targeted research by London branches of Butterfly Conservation confirming how widespread populations have become. An increase in disease-resistant elms having been planted across the city could account for the White-letter Hairstreak’s increases. I am lucky enough to have populations of both species just up the road on Streatham Common, Lambeth so come July, when they are at their most active, I will have my binoculars trained to the treetops in the hopes of catching sight of them flitting between the branches.
With its chequerboard wings, the Marbled White is one of the most striking of British butterflies and populations across the south of England have increased in distribution and abundance over the last decade. Its inclusion in Butterfly Conservation’s annual Big Butterfly Count has also helped reinforce the evidence for this species’ trends; climate change could be a significant factor in the upturn.
The diminutive Brown Argus’s adaptability has been instrumental in its increased success in London, and nationally. Once restricted to chalk grassland where its favoured larval foodplant, Common Rock-rose, grows it has now increased its range significantly by including geraniums into its diet, especially the widespread Dove’s-foot Cranesbill.
Diversification of foodplants and an increase of suitable habitat e.g. Elm trees has doubtless contributed to the upswing of some London butterflies but considering the city as a whole, in many ways, it is an ideal place for butterflies.
With 3.8 million gardens and other stable green spaces such as cemeteries, brownfield sites and parks, almost 50% of the city is considered to be green. Many of these green spaces are being more sensitively managed with few, or no, chemical interventions being used and areas being left specifically for wildlife. More and more borough councils are starting to take account of campaigns such as Plantlife’s Road Verge Campaign to ‘cut less, cut later’ in order to allow wildflowers and their associated wildlife to thrive. The road verges, waterways and railways that criss-cross the city provide important corridors for butterflies and all manner of other species to expand their ranges and develop new populations. London is also an urban heat island meaning that it maintains a warmer temperature than surrounding rural areas and butterflies fare far better in hotter climates.
Large scale projects in the capital are also helping to create butterfly habitats and promote awareness of them throughout local communities:
Brilliant Butterflies - a 2-year (2019-2021) partnership project between London Wildlife Trust, Butterfly Conservation and the Natural History Museum to restore and create chalk grassland habitats across South Croydon and Bromley.
Big City Butterflies – a 4-year (2021-2025) project by Butterfly Conservation to inspire Londoners to discover butterflies and moths and connect with their local green spaces.
Of course, there’s always more that can be done and there’s no denying the ecological crisis facing the planet but with increasing numbers of Londoners supporting butterflies by recording sightings on apps such as iRecord; planting pollinator-friendly plants in gardens and window boxes; engaging with their local greenspaces and supporting changes to mowing regimes, the good news story of London’s butterflies can hopefully continue.
Further details on London’s butterflies can be found HERE.
*With special thanks to Simon Saville (Butterfly Conservation) whose presentation on London’s butterflies 2020 inspired this blog