PARIS (AFP) - Only aggressive efforts to rein in global warming coupled with a rethinking of the British countryside will save many native species of butterfly, according to a study published Monday.
"Widespread, drought-sensitive butterfly population extinction could occur as early as 2050," scientists reported in the journal Nature Climate Change.
Under a business-as-usual scenario of continued greenhouse gas emissions, the odds that certain British Isles species will make it beyond mid-century are "around zero", the study concludes.
Protecting wilderness areas - and especially reducing the fragmentation of natural habitats - would give some of these gossamer creatures at least a slim chance of survival.
Such measures combined with a 2 degrees Celsius cap on global warming would boost their odds to about 50 per cent, the researchers said.
The two-degree target, benchmarked to pre-industrial times, has been embraced by the 195-nation UN forum tasked with delivering a climate-saving pact in Paris in December.
Nowhere, perhaps, have butterflies been more intensely scrutinised over the last century than in Britain.
Scientists led by Tom Oliver of the NERC Centre of Ecology and Hydrology in Britain examined some of the resulting data from 129 sites to see how 28 species responded to a severe drought in 1995.
The researches suspected that occasional bouts of drought were at least as devastating to some species as gradually rising temperatures.
While 1995 was the worst on record, such hot-and-dry spells are predicted to become more common as global warming sets in.
More than a fifth of the species, they found, experienced major population collapses during that period.
Among those hit hardest were the Ringlet, the Speckled Wood and the Large Skipper.
As critical, the researchers discovered a direct link between landscape and recovery: the more fragmented the habitat, the longer it took for populations to revive.
"Conservationists increasingly recognise the importance of reducing fragmentation of natural habitats rather than simply managing protected 'islands' in a hostile landscape of intensive farming," Oliver said by email.
Butterflies in other countries with a high degree of industrial farming that face similar climate change scenarios may also be in danger.
In areas "that are already hotter and drier, the impacts of drought may be much more severe", said Oliver.
The significance of the findings goes beyond the intrinsic beauty of butterflies and their value as part of Earth's natural heritage.
Butterflies are frequently used as a "canary-in-the-coal-mine" indicator for other types of insects.
If warming-enhanced drought has a similar impact on other species such as bees, dragonflies and beetles, Oliver said, a significant slice of our biodiversity could be under threat.
"Many of these other species provide essential functions for humans such as pollinating crops, eating pests, and decomposing waste."
The three other butterfly species that experienced population collapse in 1995 were the Small and Large Cabbage Whites, along with the Green-veined White.