For some years, the British Dragonfly Society and the Dragonfly Recording Network have focussed attention on changes in dragonfly distribution and on identifying key sites for our rarest species. While distribution mapping can show graphically how species have spread in recent years, it is a blunt instrument for monitoring dragonfly populations. It is hoped that the British Dragonfly Monitoring Scheme will yield counts from a large number of sites to provide national population indices. It will also allow Britain to contribute to a Europe-wide dragonfly monitoring initiative.
How are dragonflies doing? Will the numbers of river-dwelling species like Demoiselles Calopteryx increase with improving water quality required under the EU Water Framework Directive? Will the White-faced Darter Leucorrhinia dubia decline and other species increase as a result of climate change?
To answer these kinds of questions the British Dragonfly Society piloted the Dragonfly Monitoring Scheme in 2009. This pilot allowed us to evaluate the likely uptake by dragonfly recorders and to gauge the statistical power of the data gathered. It also collate any existing transect counts obtained using broadly similar methods.
The main aim of this monitoring is to keep a record of changes in numbers – it can be regarded as a thermometer from which you can read how well or how badly dragonflies in a country or a particular area are faring. After we have found out the cause of these changes we can begin appropriate conservation measures for dragonflies.
As well as determining national trends, the data can also be used for a particular area. Is Small Red Damselfly Ceriagrion tenellum faring better in Wales compared with the south-east of England? Is the sudden increase in Scarce Chaser Libellula fulva in south-west England due to warmer springs or has improved water quality in rivers played an important role? At the level of an individual site, the methodology can be used to monitor the effects of wetland management.
Monitoring Schemes need to have a long time span and robust dataset. The longer a project is running, the more reliable the data are. For individual sites the same applies: the longer a transect is active, the more insight one gets into the changes and developments at a particular site. Some dragonfly recorders have been diligently counting along fixed transects for a number of years, so building up valuable datasets. In combination, retrospective data may provide a potentially powerful tool to assess past changes; part of this initiative is to capture these datasets.
Tha map opposite shows the sites which were monitored during the 2009 dragonfly flight season.
The full Dragonfly Monitoring Manual and the three transect recording forms can be downloaded here:
Further information on the British Dragonfly Monitoring Scheme can be obtained from Steve Prentice, Dragonflies in Focus Officer.