Non-native moths on the rise – with no sign of slowing
Over 100 moth species have become established in Britain since 1900 – and the trend continues upward, say scientists from Butterfly Conservation
The charity Butterfly Conservation reports that the rate at which moth species have become newly established in Great Britain has continued to rise steadily – at around 21 % more species per decade – and shows “no sign of saturation”.
In a major review covering 1900 to 2019, the organisation found that of 116 moth species that had established in Britain, 67 % arrived by natural colonisation, while 33 % arrived with human assistance. Butterfly Conservation states that “in each decade 21 % more moth species became established than in the decade before”.
“The United Kingdom is one of the most ecologically degraded nations on Earth,” the charity notes, pointing out that while new arrivals can intrigue naturalists, a minority of non-native species can become invasive and threaten native biodiversity.
The analysis showed that species arriving naturally — so-called immigrants — accounted for the bulk of new arrivals, with a steady increase of around 22 % per decade. Those adventive species arriving aided by humans rose even more sharply, at approximately 26 % per decade. The charity writes, “collectively … the number of non-native moths establishing has increased over the last 120 years and shows no sign of slowing down”.
Butterfly Conservation goes on to say that the patterns suggest long-term environmental change is a key driver: “The rate … most closely matched by natural colonisers feeding on native host plants suggesting that long term changes in climate, as opposed to recent rapid anthropogenic warming, are playing a role.”
The charity emphasises that even though some new species may appear beneficial for species diversity, the accelerating rate of establishment raises real concerns: “In the future … we can expect more non-native species to establish in Great Britain. This will … result in greater moth species diversity, but also an increased risk of invasive species with detrimental impacts.”
In light of their findings, Butterfly Conservation stresses the urgency of improved biosecurity: “Therefore, the accelerating rate of establishment found here highlights the importance for effective biosecurity measures for imported goods.”
October 2025
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