1. Nick Isaac Arco van Strien*, Tom August & David Roy Biological Records Centre, Centre for Ecology & Hydrology *Statistics Netherlands Extracting trends from citizen science data @drnickisaac #BES12

2. Biological Recording as Citizen Science Perring, F H, & Walters, S M, eds 1962 Atlas of the British Flora. Thomas Nelson & Sons, London

3. Atlases: Stock & change in distribution

5. Where are we now? Atlases provide a rather static view of biodiversity Increasing demand for quantitative information The unstructured nature of the data makes square counting unreliable New methods for estimating trends are being developed

6. Detecting and attributing change Trends in the distribution of 8 common ladybirds A majority show substantial negative response to arrival of Harlequin ladybird Similar patterns in GB & Belgium Roy, HE, Adriaens, T, Isaac, NJB et al. (2012). Invasive alien predator causes rapid declines of native European ladybirds. Diversity and Distributions, 18(7), 717–725 Mike Majerus

7. Talk outline Counting squares is unreliable Comparison of candidate methods Simulations of recording behaviour Which methods are useful for detecting trends? Applications: which species are declining?

8. Extracting trends from biological records

9. Recording intensity has increased over time

10. Most lists are incomplete For most groups, ~50% of lists are single species

11. Lists lengths are not constant over time

12. Recording is biased in space Orthoptera 1970-2011: top 4 recorders made 14% of all visits

13. Talk outline Counting squares is unreliable Comparison of candidate methods Simulations of recording behaviour Which methods are useful for detecting trends? Applications: which species are declining?

14. Simulations Aims: 1.To compare the performance of different methods for estimating range change under realistic scenarios of recorder behaviour 2.To discard methods that are inappropriate 3.To derive rules of thumb for when other methods are appropriate

15. Type I Error Rates Even Recording Change Index 0.003 nRecords 0.027 List Length 0.055 Visit Rate 0.058 MM2sp 0.069 MM4sp 0.064 Frescalo 0.023

16. Type I Error Rates Even Recording Increasing Intensity Change Index 0.0030.017 nRecords 0.0270.998 List Length 0.0550.046 Visit Rate 0.0580.047 MM2sp 0.069 MM4sp 0.0640.068 Frescalo 0.0230.121

17. Type I Error Rates Even Recording Increasing Intensity Incomplete even Incomplete increasing Change Index 0.0030.0170.0010.004 nRecords 0.0270.9980.0420.884 List Length 0.0550.0460.050.056 Visit Rate 0.0580.0470.0560.9 MM2sp 0.069 0.0430.481 MM4sp 0.0640.0680.070.08 Frescalo 0.0230.1210.0480.061

18. Power to detect a genuine decline Even Recording Change Index0.574 nRecords0.642 List Length0.713 Visit Rate0.739 MM2sp0.665 MM4sp0.615 Frescalo0.612 A 30% decline is detectable in ~60% of datasets

19. Talk outline Counting squares is unreliable Comparison of candidate methods Simulations of recording behaviour Which methods are useful for detecting trends? Applications: which species are declining?

20. Odonata trends 1970-2011 Broad agreement between methods 14/32 species show significant increases under both methods 2/32 show significant declines under both methods

21. Odonata trends: winners Wikipedia Commons Small red-eyed Damselfly (Erythromma viridulum) Scarce chaser (Libellula fulva) Emperor Dragonfly (Anax imperator)

22. Odonata trends: losers Variable damselfly (Coenagrion pulchellum) Blue-tailed Damselfly (Ischnura elegans) Common Blue Damselfly (Enallagma cyathigerum)

23. Past, present and future Attributing changeDescribing changeBiodiversity Indicators

24. Past, present and future Attributing changeDescribing changeBiodiversity Indicators

25. Conclusions We have the tools to model biodiversity change using citizen science data The simulation provides a framework for comparing methods under a range of recording scenarios We’re only just beginning to exploit the potential of these historical data

26. Acknowledgments Colin Harrower, Helen Roy, Michael Pocock, Gary Powney, Chris Preston Mark Hill @drnickisaac #BES12