(AP) -- Global warming is rescuing the once-rare brown Argus butterfly, scientists say.
Man-made climate is threatening the existence of many species, such as the giant polar bear. But in the case of the small drab British butterfly, it took a species in trouble and made it thrive.
It's all about food. Over about 25 years, the butterfly went from in trouble to pushing north in Britain where it found a veritable banquet. Now the butterfly lives in twice as large an area as it once did and is not near threatened, according to a study in Friday's issue of the journal Science.
Decades ago, the brown Argus "was sort of a special butterfly that you would have to go to a special place to see and now it's a butterfly you can see in regular farmland or all over the place," said study co-author Richard Fox, an ecologist at Butterfly Conservation, a science and advocacy group in the United Kingdom.
Global warming helping the brown Argus is unusual compared to other species and that's why scientists are studying it more, said study co-author Jane Hill, a professor of ecology at the University of York.
Biologists expect climate change to create winners and losers in species. Stanford University biologist Terry Root, who wasn't part of this study, estimated that for every winner like the brown Argus there are three loser species, like the cuckoo bird in Europe. Hill agreed that it's probably a three-to-one ratio of climate change losers to winners.
As the world warms, the key interactions between species break down because the predator and prey may not change habitats at the same time, meaning some species will move north to cooler climes and won't find enough to eat, Root said.
"There are just so many species that are going to go extinct," Root said.
What makes the brown Argus different is that it found something new to eat, something even better than its old food, the less common rockrose plant, Hill said. The new food is a geranium and it is more widespread.
"It's almost like the whole of the buffet is now open to it," Hill said.
Explore further: British butterfly popuation is decreasing
"Temperature-Dependent Alterations in Host Use Drive Rapid Range Expansion in a Butterfly," by R.M. Pateman; et al. Science: http://www.sciencemag.org