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The Decline of Butterflies May Bring Dire Consequences for Life on Earth

Entomologist Josef H. Reichholf has been watching butterfly populations decline over the past 50 years.

A butterfly is seen on the green grass in Ratchaburi province, Thailand.

Butterflies are a symbol of beauty and metamorphosis, and one of few universally beloved insects. Indeed, few would think twice at squashing a fly or spider, yet butterflies inspire reverence. Both ancient Egyptians and Aztec believed that butterflies would greet the virtuous in the afterlife; multiple cultures around the world associated butterflies with the soul. In Western culture, they’re an eternally popular (if clichéd) tattoo decision.

So embedded are butterflies in human culture that it is hard to imagine a planet without them. Yet that seems like the kind of world that we are headed for, at least based on current ecology trends.

“In the last 50 years, our moth and butterfly populations have declined by more than 80 percent,” writes Josef H. Reichholf, an entomologist who recently penned a book, The Disappearance of Butterflies. “Perhaps only older people will recall a time when meadows were filled with colorful flowers and countless butterflies fluttered above.”

Reichholf’s recent book is a paean to these beloved insects. In it, he regards butterflies not merely as a symbol for sensuality or visual splendor, but as animals with personalities. As Reichholf explains, they experience a complicated life cycle, their bodies constantly transforming and changing, an existential ordeal likely incomprehensible to the human mind.

They are also, Reichholf says, astonishingly sophisticated in unappreciated ways. For instance: their penchant for drugs.

“Butterflies can get drunk to some degree by sucking substances with psychopharmacological effects,” he told Salon.

I interviewed Reichholf over email about his book and the future of butterflies. As always, our interview has been condensed and edited for print.

Can you explain the contrast between butterfly populations when you started studying them in the late 1950s with what they are now? What have you personally observed?

Quite vividly. I remember the lots of butterflies flying over the meadows when I was walking towards the river to observe birds [at] the River Inn in southeastern Bavaria in the early 1960s. The butterflies were of all the different kinds, from swallowtails to the then-very abundant blues, not only cabbage whites as now it is the case. However, studying diversity and abundance of night-flying Lepidoptera, the “moths,” revealed the ongoing trends over the next decades.

While average species diversity decreased roughly by half in the last ten years, abundance fell to a level as low as 15 percent, compared to the numbers of the years from 1969 to 1979, at the margins of the village in the southeastern Bavarian countryside.

Whereas this place of study borders directly the agricultural landscape, which had been exposed to extensive changes in use and input of fertilizers as well as in agrochemicals, there happened no significant changes in species diversity and abundance of Lepidoptera and other insects in the river and forest close by, where I kept running the same type of light traps in the same nights from the early 1970s onwards. And similar investigations which I made in the city of Munich in the 1980s and from 2002 to 2010 revealed no decrease despite some major fluctuations in the abundance of night-flying insects. It is important to note that now in Munich the level abundance of insects is higher than on the countryside dominated by the agricultural landscape.

At one point you describe how purple emperors get drunk, literally, on toad poison. Can butterflies get “drunk” in the same way that we do? Why do they do this?

Not only butterflies can get drunk to some degree by sucking substances with psychopharmacological effects, but as it is well known also to beetle collectors that many beetle species can be lured with alcohol-containing saps, some of which develop naturally if sugar-containing sap ferments by virtue of microbes present in nature. A number of mammals “like” alcohol-containing fruits, and birds do that as well. They have an enzyme in their livers which enables the decomposition of the alcohol, called alcohol-dehydrogenase.

Can you break down the life cycle of the average butterfly? Most people believe that it’s as simple as a caterpillar creating a cocoon and transforming into a butterfly, but your book complicates that a bit.

We have to look a bit closer into the life cycles of the butterflies and moths, which are much more dominated by the needs of the caterpillars than by those of the adult flying stage. The caterpillars are the “feeding stage,” which precedes the “mating stage” of moths and butterflies when they emerge from the pupae. There are two very basic requirements of the feeding stage — namely the proper food plants, as many Lepidoptera are quite specialized in their food choice; and a favorable microclimate in their habitat, conditions of which can be very different from that officially measured at the meteorological stations.

For completing the annual cycles, the different species also must be able to survive through the winter, which may be in either stage as an egg, a caterpillar, a pupa or even as a hibernating butterfly (like the brimstone). General meteorological trends, therefore, reveal little about the weather’s real influence on the insects.

Like so many ecological catastrophes, this one can be linked to industrial agriculture. What can we do to save them?

My studies reveal, like so many others, the overwhelming influence of agriculture on insect populations. It is better now for butterflies and moths to try to live in cities than on a countryside dominated by agriculture.

Reducing the amount of pesticides, however, as necessary and desirable as it certainly is, will not be followed closely enough to become convincing by increases of insect abundance. The predominating factor, at least here in Central Europe, is the over-fertilization of the landscape. The availability of nitrogen compounds in wide excess of the real demand favors the growth of a few plant species besides the field crops, thus reducing food plant diversity, and creating much wetter and cooler microclimates than normal for the sites due to the excessive growth of vegetation. Greatly reduced food plant diversity and too cold a microclimate are the key factors in the demise of butterflies and of most moth species and a lot of other insects, which aren’t agricultural pests.

Reducing the amount of fertilizers, therefore, would be paramount in the political strategy for more insect conservation. Our nature reserves are too small and too subject to side effects from the modern agriculture to enable thriving populations of butterflies, moths and other desirable insects.

Confronted with the fact, that more than a third of the agricultural products which people in Germany by in the supermarkets are disposed into the garbage, a lowering of the agricultural production level by some 25 per cent would not influence the food security for people, but greatly reduce the amount of fertilizers and pesticides used for maintaining the now so extremely high production level.

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