Official Statistics

Butterflies Development Plan

Updated 2 February 2024

Applies to England

Butterfly Statistics: Development plan February 2024

In line with our commitment to the Code of Practice for Statistics, we have published our plan for developing these statistics further. This plan outlines what we hope to do to improve our publications in future. This plan is informed by responses to a recent user engagement exercise for the Biodiversity Indicators and an assessment of these statistics by the Office for Statistics Regulation. We are keen to hear feedback from users of these statistics, please send your feedback to: Enviro.Statistics@defra.gov.uk.

We will look to update our development plan at least annually.

1 Developments planned for the next statistical release to be published in 2024:

• Review the species to be included in all measures and incorporate any additional species where data availability allows.

As data becomes available for more species, we will incorporate them into the indicators wherever possible, providing users with a better understanding of how butterflies are faring.

• Consider adding assessments of the indices for the UK and England ‘all-species’, and the species of butterfly in the wider countryside on farmland and in woodland in the UK.

Currently these indices are not assessed (for example, as improving or deteriorating over different time periods), and we will explore with the data provider whether this is possible. This approach will provide users with a more comprehensive understanding of how butterflies are faring, as well as allowing more meaningful comparison across the indices.

• Consider combining both the UK and England releases into a single release.

Currently, we produce two separate releases, but we believe consolidating the UK and England statistics in to one single release would enhance the user experience. We are keen to hear from users on whether this change would be welcomed.

• Consider the ordering of the indices in the release to simplify interpretation.
• Review the species-level commentary and attempt to present it more clearly, possibly in table form or as a bullet list.

We believe we can enhance the interpretation of the statistics by presenting the species-level commentary in a different format.

• Provide further information on sampling intensity and bias, including the number of sites monitored since 1976.

Information, including a map of sampling sites, was added to the 2023 release but we are exploring additional information that can give users a better sense of how representative the latest year’s sample is compared with previous years.

2 Longer term development plans:

Below are actions we are advancing with the data providers. This work will take slightly longer and will be part of post-2024 statistical releases.

• Review the performance of the Freeman method for butterfly data and consider how to adapt it further if appropriate.
• Consider alternative methods for assessing change in the indices. For instance, consider basing assessments on the annual average rate of change.
• The standard time periods for assessing the indicators are from the beginning of the time series to the current data point (long term), and the last five years of the time series (short term). Review these time periods with the data provider and consider introducing alternative time period which might be more appropriate to butterflies.
• Carry out some follow up user engagement work to gauge the impact of our developments on the value of the statistics for their users.