Sunday, April 27, 2008

Habitat loss and climate change hit dragonflies

By Paul Eccleston
Last Updated: 12:01am BST 21/04/2008

Britain's dragonflies are on the move from a twin threat posed by habitat loss and climate change.

The survival of some species is in doubt mainly because they have been ousted from their traditional haunts by human activity.

Southern hawker (left) and Common darter (right)

The British Dragonfly Society (BDS) says 36 per cent of the 39 dragonfly species are in decline.

And three species - Dainty damselfly, Norfolk damselfly and Orange spotted emerald - have disappeared altogether in the past 50 years.

Increasing loss of their wetlands home and the arrival of competing species from Europe and even north America is leading dragonflies to move further northwards to find new breeding grounds.

Dragonflies are sun-lovers and normally the more southerly species, which are not equipped to deal with lower temperatures further north, would stay put. But warmer temperatures are encouraging them to chance their luck further afield.

But this is in turn is putting pressure on resident and mainly endangered species found in Scotland who are being squeezed and left with nowhere else to go.

BDS Conservation Officer Katharine Parkes said: "Dragonflies have been around for 300m years and have survived the extinction of the dinosaurs and several ice ages...but can they survive the increasing pressures imposed by mankind?

"Understanding where and how quickly our dragonflies are moving will help us to plan for the future, with particular regard to the way in which conservation is carried out - it will be very important to make sure we are providing our wildlife with the best opportunities to react to changes. They are temperature-sensitive, making them useful for climate change impact studies."

The BDS is looking for volunteers to help record dragonfly activity in their own area and says it will provide full training and instruction.

The data collected will be used to make conservation decisions and to monitor endangered species and to help them recover. Records of breeding activity are of particular importance for identifying key sites.

Migrant hawker (left) and Common blue damselfly (right)
Migrant hawker (left) and Common blue damselfly (right)

The BDS says a new national atlas is urgently required because the range and number of species is changing rapidly. When the last dragonfly atlas was published in 1996, the Small red-eyed damselfly had never been seen in the UK but now has breeding colonies from Devon to Norfolk and is continuing to spread.

As well as the threat posed by alien invaders new fish species introduced into ponds and lakes are also taking their toll either by eating the dragonfly larvae or by muddying waters as they forage for food which disrupts larvae development.

Dragonfly facts

  • Dragonflies do not sting or bite humans!
  • They eat vast quantities of mosquitoes and midges.
  • They are useful indicators of both aquatic and terrestrial habitats due to their life cycle.
  • They are visual hunters and can see in colour as well as ultraviolet light and polarised light, which enables them to see reflections of light on water. They spend at least a year as a larva under water, then feeding/roosting/mating above ground as adults for up to two months.
  • They are voracious predators. Adults feed on flying insects, especially small flies, midges and mosquitoes. Some of the larger species, such as the Emperor, will take butterflies and damselflies.
  • They can fly at over 25 mph.
  • They have been around for over 300 million years.
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