Butterfly Conservation's Policy Advocate Officer, Kieran Thomas, explains why hedgerows are such a critical habitat for butterflies and moths and what we can do to help them thrive.
Imagine you’re a butterfly, one that is capable of flying to great heights – perhaps you’re a Painted Lady, flying thousands of feet above the countryside on your summer migration, or a Holly Blue circling around treetops looking for nectar and sap. From your vantage point you have a ‘butterfly-eye view’ of the surrounding landscape. You see cultivated fields, meadows, ancient trees, woodland patches, ditches, and more.
And joining them all together you see hedgerows: tens of thousands of miles of them, criss-crossing the landscape, forming a network between the otherwise disparate habitats, the capillaries of the countryside. Now look closer at the hedgerows. Perhaps you’re a Brimstone butterfly, flying alongside a hedgerow to find your way between woodland patches. From this vantage point you can see that the corridor you’re using is not a mere highway; it is itself teeming with life.
Hedgerows are both paths and destinations for so much of the UK’s wildlife, including many of our butterfly and moth species (64% of our butterfly species can be found at hedgerows, for example) – they provide shelter and sustenance, as well as links between different habitats.
Many species use hedgerows as we use roads; they are an identifiable route between destinations, with amenities along the way, (such as nectar sources and branches to rest on). Some species live in close proximity to hedgerows, in surrounding pastures and meadows. For these species, hedgerows may act as a windbreak or offer refuge from the extremes of hot and cold, wet or dry, in the more stable microclimate of its shadow. Other species live in the hedgerows themselves – they may be hedgerow born-and-bred, or seasonal visitors finding overwintering sites or summer nectar sources.
Let’s dive in to two of our hedgerow species and explore just how important hedgerows are for supporting wildlife, as well as how we can support them to thrive.
Brown Hairstreak
The Brown Hairstreak is one of Butterfly Conservation’s priority species. This previously widespread species is now one of the UK’s rarest butterflies and one of the species most closely associated with hedgerows – indeed the severe decline in Brown Hairstreak numbers over recent decades is almost entirely attributable to a loss of hedgerows across the country and to intensive hedgerow trimming that destroys much of their habitat.
The reason for Brown Hairstreak’s close association with hedgerows is that its caterpillar foodplant, Blackthorn, is a common hedgerow plant. Eggs are laid on young growth parts of the plant – these are the parts most susceptible to removal and destruction by hedgerow trimming. Frequent (annual) trimming severely limits opportunities for Brown Hairstreak to lay their eggs and for the eggs to hatch.
Conservation efforts for this species tend to be focussed on ensuring young Blackthorn growth has several years undisturbed. Leaving longer between each trim and leaving parts of the hedgerow uncut during each trim, greatly benefits Brown Hairstreak, giving them a better chance to establish robust colonies at each site.
In addition to changing how we maintain existing hedgerows, Brown Hairstreak also benefits from habitat creation. Creating new hedgerows, containing a good proportion of Blackthorn, allows existing populations to colonise new patches and improves the population as a whole. Coppicing and laying existing hedgerows produces the young growth so important to this species.
Conservation efforts can be further enhanced by avoiding the spraying of agrichemicals, such as pesticides, close to hedgerows, as these can be harmful to caterpillars, as well as to many other types of wildlife.
Barberry Carpet
The Barberry Carpet is a moth that is limited to a small number of sites across the UK and is afforded the highest levels of legal protection due to its precarious status. As its name suggests, this moth, specifically its caterpillars, feed on Barberry (a plant in the Berberis genus, hence the species name), which is commonly found in hedgerows.
Barberry Carpet suffered initial declines in the UK during the 19th Century, when Barberry plants were removed due to their role as a host plant for stem rust, a fungal disease affecting wheat. Since the advent of resistant wheat strains, efforts have been made to bolster Barberry populations across the UK, owing to its high wildlife value, particularly for the now rare eponymous moth.
Indeed, Barberry planting efforts were the basis of the Back from the Brink project aimed at Barberry Carpet, with new planting linking isolated colonies of the moth in Dorset, Gloucestershire and Wiltshire, and over 4,000 plants planted over the four-year course of the project, a task that involved members of Butterfly Conservation branches in these areas.
As with Brown Hairstreak, trimming regimes have a significant role to play in protecting this species. Caterpillars feed on Barberry plants well into the autumn, so trimming later in the year, and leaving areas untrimmed, is hugely beneficial to this species. Unfortunately, most advice on hedgerow trimming suggests September cuts, which is potentially very damaging to this and many more butterfly and moth species. Find out more about what Butterfly Conservation is doing about this here.
Protect our hedgerows
Hedgerows are a vital part of the ecological infrastructure of the UK. They are homes and highways, providing habitat for many species and providing corridors between habitats for many more. Hedgerows provide food for caterpillars and adults, roosting sites, overwintering sites, seasonal resources and shelter; they are important not only for their permanent residents, but those species in the wider landscape as well.
As well as benefitting butterflies and moths, hedgerows support thousands of other wildlife species across the UK, they are part of the environmental culture of our countryside, they benefit farmers and landowners in myriad ways, and they are one of our best tools in fighting the nature and climate emergency.
Find out about what Butterfly Conservation is doing to protect hedgerows across the UK here.