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A recent report from the charity Butterfly Conservation and the agricultural research station Rothamsted Research has cast a revealing light on the status of Britain’s moths.  The report is based on analysis of data from light traps, to which the insects are attracted (like a moth to a flame…) and safely held so they can be identified before release.  The study uses trapping records dating back to 1968 from a nationwide network of traps, and thus represents a uniquely comprehensive overview of trends in moth populations.

Unfortunately, it’s not good news.  The report reveals that populations of two-thirds of Britain’s macro-moths declined since 1968, with some suffering drastic declines, and 62 species suffering extinction in the 20th Century.  Population declines were more marked in southern England than in northern areas of the British Isles.  The study also identifies a (much smaller) influx of previously unrecorded species, with 27 new moths found here since 2000.

Garden Tiger (Arctia caja) : 92% decline in 40 years

Garden Tiger (Arctia caja): 92% decline in 40 years

There are several factors thought to be driving this general decline, notably urbanisation and habitat loss, and increased use of agricultural and garden pesticides.  It also seems that climate change – an increasingly significant pressure on biodiversity – is exerting a measurable effect on moth populations; for example, warmer conditions in the north of Britain may contribute to the less drastic population declines there relative to the south (which has also suffered the most intense habitat depletion).  Climate change is also thought to be encouraging the colonisation of southern areas by continental species new to the UK.

Although this significant report did attract some mainstream media attention, it’s fair to say that this decline will, in practice, not trigger widespread concern.  Although UK moth species outnumber butterfly species by over 40 to one, moths are much less appreciated than their more glamorous relatives.  Popular interest in nature conservation all too often foregrounds more attractive or charismatic species, and neglects the less prominent or “important”, a bias also reflected in conservation biology research.  Moreover, despite the essential role moths play in ecosystems – the Rothamsted report estimates a mind-boggling 35 billion caterpillars are eaten by chicks of Blue Tit (Cyanistes caeruleus) in Britain every year! – moths are easily overlooked and unappreciated.

This is a shame.  Moths are a fascinating group, with names that seem to evoke the world of the 18th Century naturalists who first named them.  True Lover’s Knot, Figure of Eighty, The Confused, Archer’s Dart, Green Horned Fairy, The Sprawler, Merveille du Jour, Scarce Silver Lines, The Lackey, Maiden’s Blush, Dark Dagger, Angle Shades, Red-Necked Footman: it reads like a list of characters from some fantasy novel.  For me, moths have a definite air of mystery about them, an association reinforced by the fact that most fly only at night.

Most of us are familiar with the classic sight of a disorientated moth fluttering around a candle or lightbulb, perhaps to its doom; it is drawn to the many artificial light sources with which humans have blitzed the night, and is suddenly blind to the moon its ancestors have followed for millions of years.  When one of these mysterious, less-appreciated Lepidopterans careers confusedly towards the light, we’re seeing a mysterious denizen of the natural world colliding headlong with the inhospitable human-dominated one, and often coming off worst.

However, the same phenomenon can be used deliberately and benignly to study moths via light traps, and thus inform measures to conserve them and their habitats.  I hold out hope that the light shone on the moth decline by this recent report may increase the will to address it.

“If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos.”

E. O. Wilson

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