The UK is one of the world’s most nature-depleted countries – in the bottom 10% globally and last among the G7 group of nations, new data shows. It has an average of about half its biodiversity left (53%), far below the global average of 75%, a study has found. A figure of 90% is considered the “safe limit” to prevent the world from tipping into an “ecological meltdown”, according to researchers. The assessment was released ahead of a key UN biodiversity conference. (https://www.bbc.com/news/science-environment-58859105)
Here I will take the UK’s butterflies to see how depleted her species list has become. The British race of the Large Copper butterfly was lost forever in the 1860s, a victim of habitat loss when its wetlands were drained. By the start of the twentieth century, Britain held 62 butterflies which comprised resident breeding species and the regular migrants, which also breed in Britain. Some areas were so rich in butterflies as to be meccas for Victorian and Edwardian collectors. The New Forest, in Hampshire, was a butterfly paradise. For over a century, gentlemen, usually from the upper and professional classes, flocked to the forest’s boarding houses and inns for a collecting holiday. Treasured specimens and livestock were traded, and an unusual specimen could pay for the entire holiday.
Local people were gainfully employed in late spring and in July especially, selling insects, acting as guides, providing accommodation, food, drink and transport (pony hire). In some years butterflies were remarkably abundant. Sydney Castle Russell describes a visit during the hot summer of 1892:
As I walked slowly along, butterflies alarmed by my approach arose in immense numbers to take refuge in the trees above. They were so thick that I could hardly see ahead and indeed they resembled a fall of brown leaves.
The summer of 1893 was even better. One recorder reported mass abundance:
...the said bed of the stream for more than a mile was literally crowded with butterflies, the bulk of them being adippe (High Brown Fritillary, now extinct there), paphia (Silver-washed Fritillary) and sibylla (White Admiral).
The great figure of British butterflies in the late nineteenth and early twentieth century, FW Frowhawk (1861-1946) first visited the forest in July 1888. He was stunned by the abundance he witnessed:
I shall never forget the impression it made…Butterflies were in profusion. A. paphia (Silver-washed Fritillary) were in hordes, the variety valezina was met every few yards, as were A. adippe (High Brown Fritillary). L. camilla (White Admiral) were sailing about everywhere…N. polychloros (Large Tortoiseshell) was of frequent occurrence.
Butterfly paradises also existed on the rolling chalk grasslands of southern England, where collectors sought unusual varieties of the Chalkhill Blue or the rarer prize, the Large Blue. The time of plenty and carefree innocence was not to last. World War I killed many butterfly collectors, whose activities had little or no effect on butterfly abundance. The decisive blows were inflicted by modern silviculture, which removed native broadleaved trees for non-native, fast-growing conifers. Coppicing virtually ended in remaining native woods, darkening the woodland floor, shading out foodplants. Chalk grassland was ploughed up for intensive agriculture, with grasslands comprising Rye-grass and White Clover and crops replacing precious species-rich butterfly habitats.
Changes in the ways remaining chalk and wet grassland were managed also took their toll.
The Mazarine Blue, still widespread and common in Europe, went extinct in 1903. The Black-veined White followed in 1922. The Large Tortoiseshell, still found in Northern France and most of Europe, vanished in the late 1940s, the Chequered Skipper became extinct in England in 1976, the Large Blue followed soon after, in 1979. The Heath Fritillary almost vanished in the 1980s and is now confined to ground comprising c.1km square. The High Brown Fritillary is in very serious trouble, despite some efforts to conserve it, and this large fritillary may well be lost. The Pearl-bordered Fritillary might yet be lost.
Consider the views of Professor Jeremy Thomas on the likely fate of the High Brown Fritillary and Duke of Burgundy:
The most notable casualties (of the deteriorating habitats in woodland) are the Duke of Burgundy, and the High Brown and Pearl-bordered Fritillaries. Despite some local conservation successes, it is a moot point whether the High Brown Fritillary or the Duke of Burgundy is the next most probable butterfly to become extinct in the British Isles (Thomas and Lewington, 2014).
Most of the attempts to restore extinct species have failed. One species, the Large Blue, has been reintroduced but from Swedish stock. The British race is extinct. An attempt is currently underway to return the Chequered Skipper to a single woodland site in England but the butterflies being used are from Belgium.
Many other species, while not endangered, have retreated. Data from the UK that covers the period 1976-2014* shows a worrying picture. A range of species including the Dingy Skipper, Grizzled Skipper, Wall Brown, and Small Heath have declined. The local extinction of Wall Brown colonies across a huge tract of southern Britain is reflected in a 77% decrease in occurrence (distribution) and an 87% decrease in abundance (population size) 1976-2015. Only six other butterfly species show a greater long-term decrease in occurrence and only three have more severe population declines in the UK.
Regarding the Small Heath, the new fine-scale assessment of distribution data (this species appears to be holding its own if one only considers its presence in 10 km squares) shows that the Small Heath has decreased by 57% since 1976, while its abundance on monitored sites has also more than halved over the same period. To put this into context, the Small Heath has fared worse than the Grizzled Skipper, Small Blue, Northern Brown Argus or White Admiral, despite being much more widespread than any of them (Small Heath is the 11th most widespread UK species based on occupied 10km squares in the 2010-2014 BNM survey).
Overall, the UK Butterfly Monitoring Scheme (which monitors population abundance annually on sites) results show that 57% of individual species had decreased in abundance since 1976, although not all these trends are statistically significant. Among the 33 species with statistically significant long-term trends, 61% decreased over the period.
Analysis of the Butterflies for the New Millennium recording scheme data reveals that 70% of species decreased in occurrence over the period 1976-2014.
The destruction and deterioration of habitats because of land-use change (e.g., intensification of agriculture, changing woodland management) are still considered the prime causes of long-term decline among habitat specialist butterflies (species restricted to specific habitat types) in the UK. However, the factors responsible for the decreases of wider countryside species are not well understood.
The figures for the UK include Northern Ireland, where the Brimstone became extinct in the 1980s, where the Wall Brown may be extinct, with just a single individual recorded during the years 2015-2021. The Dingy Skipper and Small Blue are highly restricted in their distribution in Northern Ireland.
How healthy are butterfly populations in the Republic of Ireland? We probably lost one species, the Small Mountain Ringlet, late in the nineteenth or early in the twentieth century. We have not lost a butterfly species in the Republic of Ireland since the loss of the Small Mountain Ringlet if that species really did exist in our western mountains. Considerable doubt exists concerning this species past occurrence in Ireland.
There is much less data available for the Republic of Ireland’s butterfly populations, underlining the poorly funded state of voluntary conservation bodies and official disinterest. There are currently 35 species present in the Republic of Ireland, including three regular migrants. However, the Irish Butterfly Monitoring Scheme (this involves butterfly transects, which monitors annual population abundance on sites) run by the National Biodiversity Centre and the casual recording schemes (records from various parts of the island, not from transect counts) administered by the National Biodiversity Data Centre, the Northern Ireland Environment Agency, the Northern Ireland branch of Butterfly Conservation UK and Butterfly Conservation Ireland are accumulating this data, to be published in The Atlas of Ireland’s Butterflies 2017-2021.
Indications of the status of some species are available. Preliminary findings published in 2020** indicate a change during 2008-2019 in the Small Heath of -51%. The small number of monitored sites for the other species we really need data about means we simply do not know the status of our scarcer species as regards abundance, which is the data captured by the Irish Butterfly Monitoring Scheme.
While individual observations cannot be applied to make a confident assessment of the conservation status of our butterflies, observations in the form of casual records submitted to the databases of Butterfly Conservation Ireland and the National Biodiversity Centre suggest that some species are in strong decline. The Wall Brown is certainly in trouble, declining in occurrence and very likely in abundance. The Gatekeeper/Hedge Brown appears to have a shrinking distribution, and this appears to be the case for the Grayling which seems missing from some areas of the coast it was known from in the past. The Large Heath is quietly sliding into oblivion, alongside the Curlew, as its bogs are destroyed. Another species that relies strongly on bogs, the Green Hairstreak, is also being impacted by the mass destruction of bogs, wet heaths and other wet places.
However, while it must be admitted that while we simply lack comprehensive, scientifically robust, confirmatory data of butterfly abundance decline for most of our scarcer species, we can see the habitats used by butterflies being damaged and destroyed. Across vast areas of our landscapes, our semi-natural grasslands, to take just one example of habitat, are so modified by drainage, chemical inputs, ploughing and re-seeding as to squeeze butterflies and many species else to the few edges and corners that remain, if any suitable habitat remains, leaving sink populations that eventually disappear.
Where agricultural intensification occurs without chemical inputs, such as clearing the land of rock or rock outcrops, importing topsoil or increasing stocking rates of cattle and sheep, the vegetation also changes, making the habitats less or even unsuitable for butterflies. In many areas where habitat is not destroyed, it is neglected and changes so it loses much of its biodiversity. Neglect takes many forms, including allowing invasive, non-native plants to encroach, land abandonment, which sees traditional biodiversity-friendly management practices cease, which changes the character of the vegetation resulting in a decline in the number of species over time. The negative impacts of these changes can be experienced on adjoining land, even where the adjacent habitats have not been directly altered.
Less visible forces are likely to be exerted pressure on our butterflies. Pollution such as atmospheric nitrogen deposition and rising Carbon Dioxide levels are changing soils, vegetation, and grassland temperatures. The impact of these influences on our butterfly and moth populations will, one hopes, become clear over time. If the findings of European research pertaining to these factors apply here, we will need to consider pollution as an influence on the fate of our butterflies.
Of course, butterflies don’t exist independently of their habitats or other species. Sites poor for butterflies and moths are generally low in biodiversity. In that sense, butterflies are a great indicator of the biological health of our country. Cherish butterflies, and you cherish biodiversity. Areas healthy for butterflies are healthy for other wildlife, and for human life.
A place without butterflies is a bad place. A place without nectar, bees, grasshoppers, orchids, birds, clean soil, clean water, clean air. If a place lacks butterflies, it lacks so much more. Turning our backs on butterflies is turning our backs on ourselves.
Perhaps we should think about that?
*Fox, R., Brereton, T.M., Asher, J., August, T.A., Botham, M.S., Bourn, N.A.D., Cruickshanks, K.L., Bulman, C.R., Ellis, S., Harrower, C.A., Middlebrook, I., Noble, D.G., Powney, G.D., Randle, Z., Warren, M.S. & Roy, D.B. (2015). The State of the UK’s Butterflies 2015. Butterfly Conservation and the Centre for Ecology & Hydrology, Wareham, Dorset.
** Judge, M and Lysaght, L. (2021) ‘Butterfly populations still declining’, The Irish Butterfly Monitoring Scheme Newsletter, Issue 13.