Butterfly Numbers Saw Record Lows This Summer In The UK

A Small Tortoiseshell butterfly, one of the worst-hit species in the study. colin robert varndell/Shutterstock

Usually a staple of balmy British summer days, the UK's butterfly populations have faced an alarmingly dramatic decline this summer. New figures show butterflies have hit a record low, in what’s being called “a shock” and “a mystery.”

Among the worse hit species are gatekeepers, small tortoiseshells, peacocks, commas, and holly blues. Compared to last summer, these species have had a 40, 47, 42, 46, and 48 percent decline, respectively. 

The figures come from a citizen science project called the Big Butterfly Count. Over 36,400 people participated in the big count by taking a photograph of butterflies spotted, recording their location, and then uploading the results. There is an interactive map of the results that shows the sightings by species, date period, or habitat type.

The results are mysterious as the weather this summer in Britain was favorable for butterflies; overall on the warm side with fewer cold wash outs.

In a post on their website detailing the results, the Big Butterfly Count explained: “While the long-term trends of butterflies and moths tend to result from human activities such as habitat destruction and climate change, short-term changes, from year to year, butterfly generation to generation, are typically caused by natural factors such as the weather and populations of parasites. So, in cold, wet summers, such as in 2012, butterfly populations often crash, while in good summers, such as 2013, they bounce back.

“The results of big butterfly count 2016, however, don't fit this pattern.”

It wasn’t all bad news, however. Red Admiral numbers were up 70 percent and Green-veined Whites were up 58 percent compared to the summer of 2015.

Richard Fox, of Butterfly Conservation, which runs the Big Count, remains unsure of what caused this bizarre flip, although he speculated it could be related to Britain's unusually mild winter.

“The drop in butterfly numbers this summer has been a shock and is a bit of a mystery,” Fox said in a statement.

“The summer months were warmer than usual, yet most Big Butterfly Count participants saw fewer butterflies. Perhaps the very mild winter had a negative effect, or the cold spring, or perhaps the impacts of intensive farming and pesticides are really hitting these common species now," he added.

Whether these numbers will bounce back remains to be seen. However, butterfly conservationists are hoping projects such as the Big Butterfly Count could at least help push public awareness of the problem.

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