Botham, M.S.; Brereton, T.; Harris, S.; Harrower, C.; Middlebrook, I.; Randle, Z.; Roy, D.B.

United Kingdom Butterfly Monitoring Scheme: species trends 2018

This dataset provides linear trends, over varying time periods, for the UK Butterfly Monitoring Scheme (UKBMS) collated Indices of individual butterfly species across the UK. The main statistical values derived from a linear regression (slope, standard error, P-value) are presented for the entire time series for each species (1976 to 2018), for the last 20 years, and for the last decade. In addition a trend class, based on slope direction and its significance, and a percentage change for that time period are provided to describe the statistical trends. These trend data are provided for 59 UK butterfly species. Trends across different time series allow us to determine the long and short-term trends for individual species. This enables us to focus conservation and research and also to assess species responses to conservation already in place.

The UK Butterfly Monitoring Scheme is organized and funded by Butterfly Conservation (BC), the Centre for Ecology & Hydrology (CEH), the British Trust for Ornithology (BTO), and the Joint Nature Conservation Committee (JNCC). The UKBMS is indebted to all volunteers who contribute data to the scheme.

This work was supported by the Natural Environment Research Council award number NE/R016429/1 as part of the UK-SCAPE programme delivering National Capability.

Publication date: 2019-11-01


Study area
Temporal extent
2018-04-01    to    2018-09-30

Provenance & quality

Trends are calculated by performing a linear regression on the annual Collated Indices for each species. Indices are calculated for all species (across WCBS squares and traditional UKBMS sites) using the Generalised Abundance Index (GAI) method developed in 2016 with an additional modification that the data from each site in each year is weighted in the final stage relative to the proportion of the species flight period surveyed that year for that site. They give a statistical measure of how the abundance of each species has changed on monitored sites since 1976, over the last 20 years, and over the last decade. Because the Collated indices are only calculated for each species in years in which there was sufficient data available, the starting year for the series is later than 1976 for a number of rarer species.

Supplemental information

Correspondence/contact details

Marc Botham
UK Centre for Ecology & Hydrology
Maclean Building, Benson Lane, Crowmarsh Gifford
OX10 8BB
Tom Brereton
Butterfly Conservation


Botham, M.S.
Centre for Ecology & Hydrology
Brereton, T.
Butterfly Conservation
Harris, S.
British Trust for Ornithology
Harrower, C.
Centre for Ecology & Hydrology
Middlebrook, I.
Butterfly Conservation
Randle, Z.
Butterfly Conservation
Roy, D.B.
Centre for Ecology & Hydrology

Other contacts

NERC EDS Environmental Information Data Centre
NERC Environmental Information Data Centre

Additional metadata

Topic categories
annual,  Biodiversity Biodiversity Biodiversity butterflies,  England Lepidoptera,  Northern Ireland Scotland UK Butterfly Monitoring Scheme UK-SCAPE,  United Kingdom Wales
Species Distribution
Natural Environment Research Council Award: NE/R016429/1
Spatial representation type
Tabular (text)
Spatial reference system
OSGB 1936 / British National Grid
Last updated
12 April 2022 12:51