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Dragonfly species are colonising Britain 'at a greater rate than ever before'
Six new species of dragonflies and damselflies have arrived in Britain since the late 1990s, while a seventh has returned after being wiped out in the 1950s, according to research carried out for the British Dragonfly Society (BDS).
While the population size and diversity of dragonflies and damselflies are increasing in much of Britain, some species have seen declines, with the potential for more damaging climate impacts in the future.
The BDS' annual State of Dragonflies report lays out the details of the 56 different dragonfly and damselfly species found across the UK and Ireland. Of these, 19 species have seen 'significant increases' in their population size since 1996, while five others have 'significantly declined'.
Brian Walker, BDS Chairman, says, 'This report shows that dragonfly diversity in Britain and Ireland has increased and that many species have spread further north in recent years. One of the main reasons behind these changes is a response to climate change.
'New species and range expansions sounds like good news for dragonflies, but the speed at which new species are arriving and colonising should actually be taken as further warning about the danger of rapidly changing climate conditions.
'The evidence suggests that species favouring cooler conditions are contracting their range and certain habitats such as bogs are drying out and this is having an adverse effect on the species which rely on them.
'Dragonflies are highly mobile and can react to changes more readily than other groups, but as the report shows, even some dragonfly species seem to be adversely affected by the changes.'
The small red-eyed damselfly arrived in Britain in the 1990s. © Pam Taylor
New dragonfly species are coming to Britain
Dragonflies and damselflies, collectively called Odonata, consist of around 5,900 species. Within the order are the 'true' dragonflies, the damselflies, and a small group of dragonfly-like insects known as Anisozygoptera.
In the UK and Ireland, 56 species have been observed, of which 46 are residents or regular migrants, while the rest are rare 'vagrant' species, often where an individual is blown off course or carried by some other means to the British Isles.
Of these species, six have colonised Britain for the first time since 1996. Among these are the small red-eyed damselfly, first seen in 1999, and the willow emerald damselfly, which began colonising the UK in 2007.
The small red-eyed damselfly began its move to Britain in the late 1990s, arriving in Essex and the Isle of Wight. Since then it has spread across England, being found from Cornwall to County Durham as it pushed north.
Meanwhile, the willow emerald damselfly had only ever been found twice in Britain before the new millennium, but from 2007 onwards it has expanded rapidly northwards at a rate of around 15-20 kilometres a year.
It's not just new species that are doing well, as the emperor dragonfly, which was formerly limited to southern Britain, has also expanded its range by 56% since the 1990s to cover much of England, Wales and Ireland, with infrequent sightings in Scotland.
Climate change is attributed as one of the major factors for these new arrivals and the population growth of Odonata species. Warm summers allow for more egg-laying, while speeding up the maturation of eggs and juveniles. For newcomers, warm winds from the continent help new species cross the English Channel.
While climate change is important, a number of other factors have also been attributed to the increase in species. The restoration of wetlands, bogs and other habitats has helped species to grow in strength, alongside improvements in water quality.
The emerald damselfly has lost 14% of its population since 1970. © Iain Leach
It's not all good news
While many species have grown in number as the climate warms, the impact hasn't been beneficial to all. The report also highlights the five species which have declined across the British Isles in general, while three others have declined in specific areas.
The hardest hit is the emerald damselfly, which has seen its population fall by 14% since 1970. The species favours shallow ponds and bogs, which have begun to dry out earlier in the year as the climate warms.
Specialist species are also taking a hit, with the black darter declining by 12%. The darter is typically found in acidic bogs, pools and lakes in the northern British Isles, but bogs drying out and land management changes are having an impact.
The report warns that while climate change is broadly positive for British species at the moment, it may soon begin to have a negative impact.
Extreme weather events causing flooding and droughts can kill juvenile dragonflies, while rising sea levels can inundate important coastal wetlands. The dainty damselfly was lost from the UK in 1953 thanks to the sea flooding its breeding grounds and it only returned in 2010.
There is also a possibility that non-native species may be introduced accidentally, and if the climate becomes suitable for them then they could pose a threat to the native dragonflies and damselflies.
Organisations like the BDS are working to give native dragonflies as good a chance as possible to adapt to the changing climate. For instance, reintroduction projects of specialists like the white-faced darter to new areas of England are being carried out, while projects aiming to restore former habitats and protect existing ones are underway.
