Janice R. Andrews
The latest results from the yearly scientific count of butterfly populations show that the little tortoiseshell butterfly has seen its fastest fall on record in England, plummeting by an astounding 82% across the UK since 1976.
Scientists are puzzled by the startling decrease in the population of this formerly popular garden butterfly, and it appears that climate change is the likely cause. In 2023, the small tortoiseshell had its worst year in England, its second worst in Wales, and its joint-fifth worst in Scotland, despite having its second-best year in Northern Ireland.
The UK’s butterfly populations are depicted in mixed light by the UK Butterfly Monitoring Scheme (UKBMS), the largest and most established scientific butterfly dataset in the world. At the monitored sites, half of the 58 species had an above-average year, and the other half had below-average results.
Some species showed encouraging signs of progress in conservation: the huge blue butterfly, which was reintroduced, had its best year to yet, and the checkered skipper, which was brought back to England in 2018 after going extinct in the 1970s, had its best year to date.
But certain species, like the ringlet and the green-veined white, are still suffering from the effects of the 2022 drought. Less caterpillars survived to become butterflies as a result of the drought killing their food plants.
The small tortoiseshell’s precarious situation in southern Britain is being exacerbated by climate change, in contrast to its comparatively better summertime fortunes in northwest regions. However, other species have benefited from global warming. For example, the red admiral had its best year ever last year as a result of more birds overwintering in the UK.
A butterfly ecologist at the UK Centre for Ecology and Hydrology (UKCEH), Dr. Marc Botham stressed the use of butterfly data in determining environmental health. He emphasized that in order to protect these important species and their habitats, conservation activities and monitoring must be ongoing.
The UKBMS, which currently gathers data from more than 3,000 sites yearly, is an essential resource for comprehending changes in insect populations and how they relate to climate degradation. Long-term butterfly patterns are significantly impacted by human activity, including habitat destruction, pesticide use, pollution, and climate change, according to Dr. Richard Fox, head of science at Butterfly Conservation. He emphasized that keeping an eye on these patterns offers vital information about how local species is affected by climate change and other variables.
