What is it about?

I analysed an extensive dataset of sightings of dragonflies and damselflies (Odonata) over a 50-year period in the UK. These 450,000 sightings were of around 40 species and provided a detailed record of dates on which different Odonata species were emerging from their aquatic habitats. I found that there was a significant shift towards earlier emergence which was consistent with that observed in terrestrial species. I further demonstrated that there was a difference between two groups of species that varied in what stage they over-wintered. Those species that sat in the water over winter as eggs did not show a response to climate change while those that were larvae over winter did show a response. I infer from this that the response to climate change is caused by a decline in mortality associated with cooler temperatures in the more vulnerable larval stages.

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Why is it important?

A number of studies have demonstrated an effect of climate change on the phenology of animals and plants. This study showed that the signal was present even for animals that occupy aquatic habitats, suggesting that temperature changes influences aquatic and terrestrial ecosystems in much the same way.


A variety of responses to climate change have been detected in a variety of taxa. Among these is a change in phenology – the timing of the life cycle (like the emergence of an adult dragonfly from its larval case as shown on the right). Since some species use temperature as a cue for when to develop, as the environment warms there is a signal of earlier development in these species.

Dr Christopher Hassall
University of Leeds

Read the Original

This page is a summary of: Historical changes in the phenology of British Odonata are related to climate, Global Change Biology, April 2007, Wiley,
DOI: 10.1111/j.1365-2486.2007.01318.x.
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