Records used in the report came from both the BDS Recording Scheme and the Centre for Environmental Data and Recording (CEDaR) in Ireland.
‘State of’ reports have previously been produced for well-studied groups like birds and butterflies, and there have been other, similar reports revealing shocking declines in wildlife, both here and abroad. These indicate the profound effects inflicted on a wide range of species as a result of human activity on the planet.
The State of Dragonflies 2021 report converts half a century’s worth (1970-2019) of mostly ad hoc recording by dragonfly enthusiasts – that’s 1.4 million records from 17,000 observers – into trends. These dedicated citizen scientists have enabled researchers at the Biological Records Centre, part of the UK Centre for Ecology & Hydrology, to run occupancy-detection models that reveal significant changes in the fortunes of more than half of our 46 regular breeding and migrant dragonflies and damselflies.
No less than 19 species increased significantly (41%), whereas only 5 species (11%) declined overall in Britain and Ireland combined. A further 5 species increased and 3 species decreased in at least one of the constituent countries.
(Note: Dainty Damselfly, Southern Emerald Damselfly and Vagrant Emperor, all resident or regular migrants, each had less than 250 records in the analyses, so were considered ‘data deficient’ and excluded from our overall results, although they are discussed in the text).
On the face of it, the results we are presenting in State of Dragonflies 2021 might seem to be a good news story, but if we delve into the reasons behind the species trends, the reality is somewhat darker.
In temperate countries like ours, many flying insects, such as dragonflies, benefit as adults from hot weather – it improves their survival and helps them to find new breeding sites. So it’s not surprising that there are correlations with changes in our climate. With mobile adults and aquatic larvae, dragonflies are excellent indicators of the effects of climate change on our wetlands.
Average temperatures have risen by almost 1 degree Celsius in summer during the last 50 years. This has allowed the generalist species, with less stringent habitat requirements, to colonise new areas, most notably by expanding their ranges northwards, with some colonising England from Continental Europe and others colonising Scotland and Ireland from England or Wales.
At the same time, it seems that some of our upland and northern species are retreating. The reasons for this are less clear, but again most likely due to changes in the climate, coupled with habitat changes. While we might have predicted range contractions in Common Hawker and Black Darter, which are species typical of upland bogs, the largest decline came as a surprise: quite why Emerald Damselfly should have declined the most in occupancy is a bit of a mystery.
While climate undoubtedly does have a major influence on the distribution of insects in general, so too does the abundance and quality of the habitats where they live – which of course is wetlands in the case of dragonflies.
Three in every four ponds were lost in England and Wales in the 20th century; many boggy areas were drained; and rivers have suffered pollution from agriculture and industry. That said, many ponds and lakes have been created in recent years and efforts have been made to clean up rivers and streams. Wetlands have also been recreated in former arable areas such as the Great Fen project in East Anglia, and peatlands have been restored after forestry, for example in the Flow Country in the Scottish Highlands.
Unfortunately, the ecological condition of most of our wetlands is poor and only those dragonfly species with a wide tolerance of water quality – the ‘generalists’ – have been able to take full advantage of new wetlands such as reservoirs, farm ponds and flooded mineral workings. In this way, many species have expanded their ranges and powerful fliers, such as Emperor Dragonfly and Migrant Hawker, have even been able to colonise Scotland and Ireland.
There have also been significant range expansions in the Red Listed Norfolk Hawker and Scarce Chaser, and localised species such as Red-eyed Damselfly and Hairy Dragonfly.
Since 1995, we have seen eight species reach Britain for the first time and at least two further species have reappeared after long absences. Six species have recently established breeding populations and another, Dainty Damselfly, has recolonised after being lost in the floods of 1953. In the case of Small Red-eyed Damselfly, which first appeared in 1999, the spread has been spectacular and it now occurs from County Durham to South Wales and Cornwall. More recently, Willow Emerald Damselfly and Southern Migrant Hawker have spread over much of south-east England.
Conversely, one former regular migrant, Yellow-winged Darter, an eastern rather than southern species, has declined, and occupancy has not changed very much among most of the resident ‘habitat specialists’, which are always going to be limited by their strict habitat requirements.
Increasing species include:
Emperor Dragonfly 56%
Migrant Hawker 28%
Ruddy Darter 26%
Black-tailed Skimmer 24%
Small Red-eyed Damselfly 23%
Broad-bodied Chaser 20%
Hairy Dragonfly 20%
Declining species are:
Emerald Damselfly -14%
Black Darter -12%
Common Hawker -8%
Scarce Blue-tailed Damselfly -2%
Small Red Damselfly -2%
(Yellow-winged Darter -10%)
You can find the full report on the BDS website.