 |
||||||||||||||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
||||||||
Development of Butterfly Monitoring in the UK
The Butterfly Monitoring Scheme
Detailed population monitoring of butterflies commenced at a national scale in the UK in 1976 with the launch of the Butterfly Monitoring Scheme, co-ordinated by the Centre for Ecology and Hydrology and Joint Nature Conservation Committee.
Under the scheme, observers make counts of butterfly numbers at specific sites by weekly recording along a fixed route (transect) under favourable weather conditions throughout the main butterfly flight period (Pollard and Yates 1993).
Transect monitoring required a significant commitment: ideally 26 transect walks per year, each of which might take 1-2 hours to complete, over many years. For this reason (and because of the limited capacity to co-ordinate the scheme centrally) the number of BMS sites was constrained.
Initially, the scheme involved 34 sites across the UK, but this increased steadily to 134 sites in 2004. Most of the BMS transects were carried out at protected sites, such as nature reserves, with semi-natural habitats (biotopes). All of this effort has proved extremely valuable. It provides a standardised annual measure of the changing status of butterfly species, which can be used to generate short-term trends; something that cannot be derived from distribution recording.
Furthermore, BMS data have played a key role in many of the advances in knowledge of butterfly ecology in the UK over the past three decades (Pollard and Yates, 1993). Through the data, scientists have unravelled the dependence of butterfly populations on the climate (e.g. Pollard 1988, Pollard and Yates 1993, Roy et al. 2001). Not only has this paved the way for assessments of the impact of global warming on our biodiversity, but has greatly helped our understanding of how landscape, land-use and habitat changes affect butterflies.
The analysis of BMS data can allow for the over-riding influence of the weather, thus enabling other influences on particular butterfly populations to be detected. For example, site managers can assess the impact of small-scale habitat management and policy makers can monitor the effectiveness of national-scale agri-environment schemes (Brereton et al. 2006)
With an output of over a hundred scientific research papers and improvements in analysis of the data, the BMS went from strength to strength. Nevertheless, improvement were needed in two main areas.
Firstly, because of the limited number of sites in the scheme, insufficient data was available to generate population trends for some of the rarer species.
Secondly, most BMS sites were protected areas that are managed, at least in part, with biodiversity conservation objectives.
As a consequence, the national population trends generated by the scheme may not have been representative of the landscape as a whole. Both of these limitations are now being addressed under the UKBMS project and the future of butterfly monitoring is brighter than ever.
Butterfly Conservation's Transect project
Although the number of sites contributing to the BMS has remained limited, the scheme's transect methodology developed by Dr Ernie Pollard has been taken up by many conservation organisations, landowners and amateur naturalists.
The number of transects operating outside the BMS grew steadily at first, but increased rapidly after 1990. By 2003, over 500 transects were being recorded by more than 1000 recorders, with 80 new ones established in that year alone (Brereton et al. 2006). Although some local co-ordination of results was already being undertaken by pioneering Branches of Butterfly Conservation, national collation and analysis of all these independent transects only commenced in 1998.
Since then, support from the Department of the Environment, Food and Rural Affairs (Defra) and its predecessor, the Ministry of Agriculture Fisheries and Food (MAFF) has enabled Butterfly Conservation to co-ordinate independent transects (and other standardised survey data e.g. timed counts).
This has not only allowed the collation and analysis of an important new data set, but has encouraged and trained the people who walk transects (most of whom are volunteers). It has also streamlined the flow of data, instigated new transects in under-recorded regions and led to the development of new analysis techniques and software.
Although most transects co-ordinated by Butterfly Conservation were started relatively recently and do not have the benefit of long time-series of data, the large number of monitored sites has enabled the calculation for the first time of reliable population trends for many of the rare and threatened species, which are of greatest concern to conservationists.
Most of these will shortly be published on this website for the first time.. In addition, although like BMS transects, much of the independent monitoring is carried out on protected sites, there is a much greater range and representation of different habitat and land-use types in the Butterfly Conservation data set. Indeed, the initial impetus to collate the data was to enable an assessment of the impact on butterfly populations of agri-environment schemes in the farmed landscape.
The future of recording and monitoring
To fully utilise the large effort devoted to recording transects throughout the UK, the Butterfly Conservation Transect project and the BMS have been merged into a single scheme. With funding from a multi-agency consortium led by Defra, the UK Butterfly Monitoring Scheme (UKBMS) commenced in spring 2006.
The population data used in this website are based on this full set of transects. Over the coming years, work will continue to enhance butterfly monitoring in the UK and to develop butterfly biodiversity indicators.
Development of a suitable method for monitoring populations of common butterflies in the wider landscape (akin to the Breeding Birds Survey run by the British Trust for Ornithology) is also underway and, further afield, efforts are being made to integrate transect data from other countries to produce European butterfly trends and an international biodiversity indicator.
References
Brereton, T., Roy, D., Greatorex-Davies, N., 2006. Thirty years and counting. The contribution to conservation and ecology of butterflymonitoring in the UK. British Wildlife 17, 162-170.
Pollard, E., 1988. Temperature, rainfall and butterfly numbers. Journal of Applied Ecology 25, 819-828.
Pollard, E., Yates, T.J., 1993. Monitoring butterflies for ecology and conservation. Chapman & Hall, London.
Roy, D.B., Rothery, P., Moss, D., Pollard, E., Thomas, J.A., 2001. Butterfly numbers and weather: predicting historical trends in abundance and the future effects of climate change. Journal of Animal Ecology 70, 201-217.
