The summer heatwave in 2018 helped UK butterflies bounce back following several poor years, a study revealed on Monday.
More than two-thirds of species were seen in higher numbers than in 2017 with two of the UK’s rarest butterflies, the Large Blue and Black Hairstreak, recording their best years on record.
But 2018 was still an average year for two-thirds of UK butterflies that have been declining since records began 43 years ago.
Farming intensification, break-up of the countryside, air pollution and climate change are said to be causing the decline.
Professor Tom Brereton, associate director of monitoring at UK wildlife charity Butterfly Conservation (BC), said: “If butterflies are struggling it’s quite an alarm bell.”
Butterflies are recognised by the government as an indicator of biodiversity because their response to environmental changes is likely to reflect responses in other insects.
Insects make up more than 50% of life on land and provide services crucial to our food supply like pollination and pest control.
Professor Brereton said he enjoys seeing butterflies on country walks or sitting in the garden and that they are a big part of his quality of life.
He said: “To see butterfly biodiversity gradually get eroded year after year is quite depressing, isn’t it?
“The last time I went to London on a sunny day I didn’t see a single butterfly.”
In 2017 BC reported that butterflies are declining faster in urban areas due to increasing pressure from development, habitat loss and climate change.
But Professor Brereton said there is cause for hope.
“If we change our policies and put more resources into conservation, butterflies can and will come back. It’s in our hands, really,” he said.
Londoners can find butterflies from mid-March to the end of September in large commons and further afield in the North Downs, Epping Forest and Langdon Hills in Essex.
And there are a few things that people living in cities can do to help butterflies thrive.
In summer BC holds the Big Butterfly Count, a UK-wide citizen science campaign that Londoners can do from anywhere.
Professor Brereton said if you have a garden or a bit of green space, leave a few patches unmown and plant things like lavender, marjoram and ivy.
He also said people should cut down on insecticides and pesticides that kill butterflies and other insects and disrupt the food chain.
“We complain about farmers but I think per unit area we put more pesticides and insecticides on gardens than we do on farmland,” he said.
More than 3,000 people monitor butterflies for BC at 2,800 sites across the UK during butterfly season.
At the end of the year BC collates the data and produces annual and longer term trends.
The study published on Monday is led by BC, the Centre for Ecology & Hydrology (CEH), British Trust for Ornithology and Joint Nature Conservation Committee.
While the heatwave in 2018 did help butterflies, the extreme weather patterns increasing under climate change are damaging to them.
Professor Brereton said it remains to be seen what the knock-on effects of the 2019 heatwave will be.
Butterfly ecologist Dr Marc Botham at CEH said that thanks to ongoing habitat management many threatened species can benefit from good weather like that of summer 2018.
But he said that more needs to be done to improve the condition of the countryside so other species can also take advantage.
To volunteer or become a member with Butterfly Conservation visit https://butterfly-conservation.org