Oak Eggar - Iain Leach

Butterfly Conservation warns that Britain’s biodiversity is under threat following analysis of data from the National Moth Recording Scheme (NMRS), which has collated more than 16 million moth sightings dating back to 1769. Significant population falls from 1970 to 2010 can be attributed to our changing landscape, including agricultural intensification and urban spread, as well as climate change.

The study by Butterfly Conservation, the Centre for Ecology and Hydrology and University of York, published in the Journal of Applied Ecology, is the first to examine long-term trends for all of Britain’s resident larger moth species; common and scarce, nocturnal and day-flying. Trends for 673 species were calculated, 60% of which showed a significant change over the 40-year period. Two thirds more species declined than increased.

Moths are a key part of the food chain and act as pollinators for plants. The substantial declines revealed by this study provide further evidence of a wider crisis in insect biodiversity with knock-on effects for many species such as birds and bats and ecosystem services such as pollination.

Declines among widespread moths were most severe in the southern half of Britain which has seen greater agricultural intensification and urban spread over the last four decades. In contrast, these same widespread species showed no overall decline in northern Britain, where land use changes have been less pronounced.

A further indication of the negative impacts of intensive land use came with the finding that moths associated with low nitrogen environments (based on the preferences of the plants on which the moth caterpillars feed), such as Cistus Forester and Oblique Striped, declined in relation to those that inhabit more fertile habitats, such as the Snout and Mocha. Nitrogen enrichment of the environment (eutrophication) is a problem particularly associated with intensive farming.

Black Arches MothClimate change appears to be a much more important driving force for moths species that are restricted to warm or cold parts of Britain. Moths restricted to northern Britain, such as Northern Dart and Small Dark Yellow Underwing, tend to have declined over the 40-year study. Land use changes have been less severe in northern Britain, suggesting that the warming climate is the most likely cause of problems for this group of moths that are adapted to cool climates.

But climate change also had some positive effects. Many moths at the northern limit of their range in southern Britain, such as Jersey Tiger, Pine Hawk-moth and Black Arches, increased over time, most likely in response to warming temperatures.

Conservationists believe that the best way to safeguard the UK’s moths against the threats of climate change and changes in land use is by protecting and restoring habitats suitable for resident species and those shifting their range.

Richard Fox, lead author of the paper and Butterfly Conservation Surveys Manager said: “These results highlight the enormous importance of amateur naturalists in gathering data and underscore the damage that has been done to Britain’s wildlife over recent decades. Moths have been much maligned and under-valued but play very important roles in ecosystems, as well as acting as indicators for the fortunes of countless other insect species, and society should be concerned by the results we’ve discovered. The next step is to develop evidence-based management practices to restore habitats in farmland and forests for moths and other ‘hidden’ wildlife.”

Read the abstract or subscribe to the full report on the Journal of Applied Ecology website.