International Journal of Biometeorology

, Volume 58, Issue 10, pp 2159–2163 | Cite as

Citizen science: best practices to remove observer bias in trend analysis

  • Alemu GonsamoEmail author
  • Petra D’Odorico
Short Note


Citizen science, time series records over long periods of time, and wide geographic areas offer many opportunities for scientists to answer questions that would otherwise be impractical to investigate. Citizen scientists currently play active roles in a wide range of ecological projects; however, observer biases such as varying perception of events or objects being observed and quality of observations present challenges to successfully derive interannual variability and trend statistics from time series records. It is recommended that citizen science records, particularly those involving events such as plant phenology, should not be directly averaged across sites. The interannual variability expressed as an anomaly and trend expressed as a regression slope should be calculated for each site. Only the site level anomaly and regression slopes should be averaged to suppress observer biases.


Anomaly Citizen science Observer bias Phenology Trend analysis 



We would like to thank and commend the persistent work of John O’Keefe at Harvard Forest Experimental Forest for collecting and cataloging the unique field phenology data. We extend our thanks to the thoughtful and constructive comments of two anonymous reviewers.


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Copyright information

© ISB 2014

Authors and Affiliations

  1. 1.Department of Geography and Program in PlanningUniversity of TorontoOntarioCanada
  2. 2.Grassland Science Group, Institute of Agricultural SciencesSwiss Federal Institute of TechnologyZurichSwitzerland

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