Berlin environment blog: Reveling like only moths can | Global Ideas | DW | 30.06.2017
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Berlin environment blog: Reveling like only moths can

If you think it's only humankind that gets to party in Berlin, think again. High up in the branches of an indigenous tree, a boundless indulgence is taking place. And changing the face of the city in the process.

By my reckoning, there are eight streets in Berlin bearing the name Kastanienallee. Thus christened, it would be nice to think, for their namesakes, the horse-chestnut trees that lined their pavements, not with gold, but a glorious green, the likes of which only nature could create.

The oldest of these boulevards dates back to 1826 and has, in the past two decades, become a place synonymous less with arboreal than tourist and indeed hipster delights. But if, when passing in and out of their doors, you were to stop and look – I mean really look - at the Aesculus hippocastanum trees - which were replanted at the end of the 1990s, their leaves would reveal a level of activity every bit as hedonistic as that of the pleasure-seekers who walk beneath them.

The difference though, is that the revelers who sit atop the foliage are on a destructive mission. Cameraria ohridella are leaf mining moths. Don't be fooled by the prettiness of their name, for their larvae have been systematically wreaking havoc on Berlin's horse chestnut trees since they arrived in the capital sometime in the nineties.

Bildergalerie Biergärten in Deutschland (picture-alliance/ZB)

The green before the brown

First discovered in Macedonia in 1984, they have made themselves at home here. As they eat through the green goodness of the leaf tissue, they render them brown and withered. And they don't only pick a few leaves. No, no. They go for whole trees. Whole streets of whole trees. A whole city of whole trees. They go for maximum damage.

Autumn in August?

The first time I saw this phenomenon was several years ago, when I was living on the aforementioned Kastanienallee. It was summer and I remember coming back to the city after a while away and being gutted to see autumn had got there before me. We had collectively begun the slow slide into the unforgiving cold of winter.

Except we hadn't. Because on closer inspection, the only trees to have yielded their chlorophyll were the horse chestnuts. These poor old conker trees, tall and proud, stripped of their beauty and stature by gazillions of hungry little caterpillars. They put up a good fight, producing rich new foliage year after year, and sometimes, if the larvae get to them early enough, several times in a single season.

But no matter how often they recreate their beautiful gown, the moths are always waiting to strip them back to their bare branches. And so far, the human hand has failed to intervene with a successful cure. So far...

An old lady with a solution

Last weekend, I found myself sitting in a big old barn out in Brandenburg listening to 90 year-old Eva Ullrich, former pediatrician and long-standing tree aficionado talk, among other things, about her profound love of the conker tree and sadness at their prolonged illness. But she also offered a simple solution: Red horse chestnuts.

Brown leaves of an infected horse chestnut tree

Not the sign of autumn come early, but of a tenacious pest

I confess, I didn't even know there was such a thing. I do now though. Just as I now know the leaf miners with the voracious appetites apparently have none for this sister species. 

After her talk, I asked Ullrich if there was a move afoot to plant these, the more resistant of the horse chestnut relatives, in Berlin. She looked at with a mixture of frustration and sadness. "Of course not," she said. When I asked why that is, she shrugged. "That," she said, "I don't know."

And so, the eight streets that take their names from the trees that line them, will likely continue to be the scene of leaf carnage. Of a host that can't get rid of unwanted guests. Of insect parties, which true to Berlin form, go on. And on. And on...