What are the biggest threats to butterflies and how can gardeners help?

An expert offers tips in the run-up to the Big Butterfly Count

Time is running out to save some of Britain’s best-loved insects, with recent findings revealing a 26% increase in the number of butterfly species threatened with extinction, according to wildlife charity Butterfly Conservation.

Last year’s Big Butterfly Count – in which the public is asked to record the number of butterflies and day-flying moths over two weeks in July and August – recorded its lowest level since the count began 12 years ago, despite more counts being submitted than ever before.

“Like much of our wildlife, butterflies are in decline. Three-quarters have either declined in abundance and/or in distribution since 1976,” says Dr Zoë Randle, senior surveys officer at Butterfly Conservation.

So, what are the biggest threats to our beautiful butterflies and how can gardeners help?

Habitat loss

“The biggest driver of change is habitat loss and land use. A lot of land is being lost to urbanisation and agriculture,” says Randle. “Land is being dug up and removed for housing and building development and other things to benefit human beings.”

Artificial grass has also reduced habitat for wildlife, while the commercial use of peat has also affected the landscape for insects.

What gardeners can do?

Stop using peat-based compost: “Peat-based compost is an absolute no-no. A lot of peat bogs, where the peat is extracted from, are really important habitat for lots of species including the large heath butterfly. Gardeners should go peat-free.”

Reduce habitat fragmentation: “There may be a patch of land that has lots of lovely species in it, but if something happens and it is no longer habitable, species need somewhere local to move to. Ideally you need a network – you could form it through a community – for those species to eat, sleep and feed, so if they lose one habitat, there is another one close by to relocate to.”

Pollution

“There’s nitrogen pollution from agriculture but also from vehicle fumes, which are entering the atmosphere and then precipitating down on to plants, which has a knock-on effect to the soil make-up and structure,” says Randle.

What gardeners can do?

Consider planting hedges: These can act as a barrier to vehicle pollution and some are a magnet for butterflies, which love blackthorn, hawthorn and older buckthorn (brimstone butterflies lay their eggs on these), Randle suggests. Their flowers provide nectar and shelter. Older buckthorn is the larval foodplant for brimstone butterflies. Plant honeysuckle and jasmine in your hedgerow to attract more butterflies.

Avoid chemicals: Don’t use chemicals which may kill your beneficial insects as well as your pests. Let nature take its course, she advises.

Climate change

More extreme weather events in the future, with heavy rains and droughts becoming more frequent, could have a devastating effect on butterflies, research has found. Some species are moving further north, but relatively sedentary species and those with decreasing population trends are seemingly less able to colonise new areas despite the warmer conditions.

What gardeners can do?

Provide food and shelter: Plant nectar-rich plants in sunny, sheltered spots and select a range of plants for different species. Leave a pile of logs for butterflies, moths and caterpillars to shelter in out of the elements.

“Some species are faring well as a result of climate change,” says Randle, “such as the peacock, comma and speckled wood butterfly. The climate further north is becoming more habitable for them.”

Excessively tidy gardens

Perfectly manicured beds and borders and lawns mown to within an inch of their life are not good for wildlife, says Randle. “There’s nothing for butterflies to feed on and nowhere to shelter from the elements.

“In summer, a lot of butterflies will be nestling into the long grass and the vegetation to stay out of the rain. If you over-manicure the lawn and remove all weeds like daisies and dandelions, there will be no nectar and no shelter,” she explains. “If the butterflies have laid eggs on grasses in the lawn, they will end up in the grass cuttings basket. They could also be decimated in the blade.”

Raking up leaves from the lawn in autumn and then burning them could also affect populations, as they overwinter on plants in our gardens. Some spend the winter as eggs stuck to the bark of trees and shrubs, hatching out the following spring when the plants begin growing again. Others spend the winter wrapped in the safety of a chrysalis or cocoon on a leaf, waiting until spring or summer to emerge as a butterfly or moth.

What gardeners can do?

Leave an area wild: Leave a patch of grass that can grow long and wild. This will encourage ox-eye daisies and butterflies can shelter there, she suggests. Allow some weeds to grow and don’t cut everything back too much at the end of the season. Rewilding part of your garden could be the answer, leaving nettles, thistles and brambles which are a great nectar source – Painted ladies lay their eggs on thistles.

Not choosing sufficient plants for pollinators

Gardeners may opt for the prettiest plant – but double-flowered types are often not rich in nectar and are difficult for the insect to access.

What gardeners can do?

Choose butterfly-friendly plants for each season: Plant a variety of nectar-rich plants which will last through to autumn and winter. “Butterflies and moths need nectar for energy. The plants should start flowering as early as possible – in spring – and have a variety of nectar plants to flower throughout the year, so there’s constantly something there for them to feed on.”

Aubrieta, bluebells, clover, primroses, forget-me-nots are all good nectar sources in spring. Summer plants for butterflies include buddleia, Verbena bonariensis, lavender, nepeta, French marigold, Michaelmas daisies, mint, red valerian, thyme and perennial wallflowers. Ivy flowers in October and November provide a rich source in cooler months.

“Make sure you have the food plant that the caterpillar lives on, and where the butterfly lays its eggs,” says Randle. “The peacock, small tortoiseshell and comma all lay their eggs on or near stinging nettles.”

The Big Butterfly Count runs from Jul 15-Aug 7. For more information visit bigbutterflycount.butterfly-conservation.org

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