Following the well documented discoveries of declines in bee and butterfly populations, ecologists from Rothamsted Research Institute and charity Butterfly Conservation have revealed that two-thirds of common larger moth species have declined by up to 99 percent in less than 40 years, with some species having been entirely wiped out.

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The State of Britain’s Larger Moths 2013 found that the Orange Upperwing, Bordered Gothic and Brighton Wainscot have all become extinct in the last 10 years; extinction of these three species follows on from the loss of a further 62 species of moth during the 20th Century.

The report on 'macro-moths' revealed that some once-common garden species, including the V-moth, Garden Tiger Moth and Spinach Moth decreased by over 90 percent between 1968 and 2007. The V-moth, Garden Dart, Dusky Thorn and Hedge Rustic declined by between 97 and 99 percent over the period studied. Losses were much greater in the southern half of Britain than the north.

By examining continuous records running from 1968 to 2007 (the longest running national population trends of insect species known anywhere in the world), the researchers were able to see that, while some species enjoyed dramatic increases, two-thirds of the species recorded declined over the 40-year study, and populations of over 37 percent were more than halved.

In Southern Britain, larger moth populations decreased by an average of 43 percent, compared to 11 percent in the North. The researchers suggested "ongoing habitat loss and the deteriorating condition of the countryside" are major factors in the observed declines.

Although populations declined by 40 percent overall in the South, researchers suggested that some effects of climate warming have proven beneficial to moths in the north, ensuring the abundance of moths remained unchanged, although many individual species still suffered declines. They added that greater habitat loss in the South has likely wrought the dramatic losses seen in this half of Britain.

Loss of moths indicates widespread environmental degradation

The researchers commented that moths, which play a role as insect pollinators, are key indicator species for assessing the health of the environment. They said their findings "point strongly to a wider insect biodiversity crisis and mirror declines of butterflies, bees and carabid beetles," adding that declines could have a knock-on effect for plants reliant on these species for pollination and animals reliant on moths for food, such as garden and woodland birds, bats and small mammals.

While many moth populations declined substantially over the last few decades, the period also saw an unprecedented influx of new moth species to Britain. More than 100 species have been recorded for the first time in Britain this century and 27 species colonised Britain from the year 2000 onwards. Climate change is seen as a major driver for these new colonisers as conditions become more suitable for continental species.

Nevertheless, despite the number of moths increasing their range to encompass the UK, the overall steep decline in moths, especially in the South, lead the study's authors to make gloomy pronouncements. Butterfly Conservation Surveys Manager and lead report author Richard Fox said last week, "This report paints a bleak picture about Britain's biodiversity. Much has been made of the decline of butterflies and honeybees but moths represent the massive, but largely un-noticed diversity of insects that form the vast majority of animal life in Britain. The severe declines are a damning indictment of how recent human activity has devastated our native wildlife."

Chris Packham, Butterfly Conservation Vice-president said in a statement "As well as being important pollinators, moths are an absolutely vital cog in the food chain for other species such as birds and bats. The dramatic and ongoing loss of moth abundance highlighted in this report signals a potentially catastrophic loss of biodiversity in the British countryside."