The State of Britain’s Larger Moths 2013 report published at the beginning of February revealed dramatic declines in moth populations. Analysis of 40 years worth of nightly moth count data from the Rothamsted Insect Survey showed that the total abundance of larger (macro) moths (all species lumped together) has decreased by 40% in southern Britain since the late 1960s. Devon moth recorders contributed to the report through the National Moth Recording Scheme and via several Rothamsted Insect Survey traps in the county.
Two thirds of the 337 common and widespread moth species analysed had decreased in abundance, with many familiar garden moths undergoing severe declines. Numbers of the Small Square-spot decreased by 87% over the 40 years (1968-2007), those of Heart and Dart by 76% and Garden Carpet by 75%. The most severe decline, a 99% decrease, was suffered by the V-moth. This once widespread ‘garden’ moth is now thought to be extinct in Devon and several other counties in southern England.
The main cause of the declines is thought to be the loss of wildlife habitats such as hedgerows and flower-rich field margins as a result of the intensification of agriculture and urbanisation. Reduced woodland management is also believed to be a factor, leading to the loss of open sunny habitats such as glades.
Some species have bucked the trend however. An amazing 27 new moth species have colonised Britain this century and others have increased their previous distributions, perhaps in response to climate change. Here in Devon, we’ve seen species such as the Vine’s Rustic, Jersey Tiger and Dingy Footman become much more widespread in recent decades and new species such as Portland Ribbon Wave become established.
The full report can be viewed or downloaded online from the Butterfly Conservation website.