A recent study in the U.K. finds that in the past two decades, huge strain on butterflies in cities has been out by pesticides, paving and higher temperatures.
According to the study, in the past two decades, compared to the countryside, butterflies have vanished from towns and cities more rapidly.
Urban butterfly abundance fell by 69% compared to a 45% decline in rural areas over 20 years from 1995 even as industrial agriculture has long been viewed as the scourge of butterflies and other insects but city life is worse.
According to the study published in the journal Ecological Indicators, butterfly species such as the small copper and small heath have suffered particularly disastrous urban declines.
While small copper abundance fell by 75% in urban areas compared to 23% in the countryside, numbers of small heath fell by 78% in urban areas compared to just 17% in the countryside, found scientists at Butterfly Conservation, the University of Kent and the Centre for Ecology and Hydrology.
The neglect of parks and pesticide-wielding gardeners who have also turned lawns and flower beds into driveways and patios, heightened effects of climate change in cities, building on urban green space, council cuts and the neglect of parks and building on urban green space are the causes of this phenomenon, said Prof Tom Brereton, head of monitoring at Butterfly Conservation and one of the study’s co-authors.
He said: “Urban areas are under massive pressure. People are paving over gardens for drives or patios and putting more pesticides on their gardens per area than are put on farmland. Bigger gardens are being sold off for development and councils have less resources for managing green spaces.”
The study found that most urban butterflies are emerging earlier and are longer-lived than the same species living in rural areas and essentially compares trends for 28 species in urban and countryside environments.
Compared to their country cousins, city butterflies emerge two days earlier on the average. Compared to those found in rural locations, urban brimstones are on the wing five days earlier.
The urban heat island effect: human activities make towns and cities warmer than the surrounding countryside, is the probable cause of the earlier emergence and longer flight periods, researchers said.
“Warming is generally quite good for a lot of sun-loving butterfly species but some species don’t like warm winters and warm springs and these effects are more pronounced in big cities,” said Brereton.
Brereton said gardeners also bear responsibility for recent declines with 87% of people having gardens or access to them – and gardens covering a greater area than all the UK’s national.
“When I was growing up in Manchester in the 1970s, no one used chemicals and everyone had a lawn and flowers and we used to see loads of greenfly as kids – you don’t really see them anymore. We need to be more tolerant of nature.”
While also allowing native “weeds” such as ivy, which is a food source for the holly blue and provides vital autumnal nectar for red admirals and other insects, butterfly Conservation advises gardeners to cut out weedkillers and pesticides and grow some native wild flowers.
“Improving the urban environment is something many of us can make a real contribution to, leaving bits of garden as wild areas, using less chemicals and gardening with wildlife in mind,” Dr Nigel Bourn, director of conservation science for Butterfly Conservation, said.
(Adapted from The Guardian)