The deadly butterfly effect: humanity sets an evolutionary trap
How farming creates a dependence among these beautiful creatures - and then causes their extinction
Where have all the butterflies gone? Go and ask the homo sapiens.
These beautiful creatures, lauded by human beings in poetry, textile design, art and literature, have fallen into what’s called “an evolutionary trap” created by us.
A new study, just published in Nature, shows how the human hand changes a butterfly’s environment, creating its dependence on what farming practices bring to an area, only to cause its extinction when those practices change.
The international team and lead researcher Professor Michael Singer, of the University of Plymouth in the UK, have used more than 30 years of research to fully document an example of this process.
They showed how, in North America, a “large, isolated population” of a certain type of butterfly “evolved complete dependence” on a weed that was introduced from Europe.
After some time, the butterfly’s existence depended on the availability of the plant and, when the plant was then eradicated, the butterflies died out.In 1993, other research – also published in Nature – made this prediction, and the new research confirms it.
So why was the weed introduced in the first place? It happened 100 years ago when cattle ranching began in this part of Nevada, and it was then that the human beings had set an “eco-evolutionary trap that the insects obligingly fell into”, and “the trap was sprung when humans suddenly removed the cattle”, withdrawing their “gift”, and driving the butterflies to extinction.
In the hay that came from Europe, there was an alien plant. The caterpillars of the local butterfly population “thrived better on it than their traditional host” and by the mid-2000s, they had abandoned their old favourite for the new.
When cattle ranching ceased the “new” plant died out. The old plant friend still existed in abundance, but it was too late.
“If the butterflies had not evolved so rapidly in response to the introduction of the plantain, they would most likely have survived,” say the researchers.What ground does this study break? A statement from the university said: “European conservation biologists have long believed this to be the process underlying many local extinctions across Europe.” The study provides “the first hard evidence of that process”.
The results are similar to those seen in British species such as the large blue butterfly, “which went extinct across southern England following a reduction of grazing by both rabbits and sheep”.
Said Singer: “This is a clear example of how humans are able to change habitats faster than even rapidly evolving species can change their behaviour.
“This cannot be an isolated phenomenon, so unless we become aware of the potential consequences of such actions we will continue to inadvertently cause population extinctions of native species, without recognising what we are doing.”