Abstract
Whilst volunteer monitoring has many benefits for both volunteers and professionals, volunteer data must be validated to understand the value and potential applications of information from volunteer monitoring programmes. Our study aimed to assess the concordance between volunteer and professional data, including state and trend assessments. We compared macroinvertebrate data collected by volunteers using a simplified identification protocol to data collected by professionals following standard national protocols for collection and identification. We found that volunteer and professional macroinvertebrate data expressed as summary indices of ecological health were significantly correlated. However, the coarser level of taxonomic identification in the volunteer dataset limited the use of taxon richness as a biodiversity measure. We also demonstrated that the ability of volunteer data to detect long‐term trends in ecological health is comparable to professional data. Overall, stream monitoring data collected by volunteers provided an assessment of stream health that was concordant with assessments based on data collected by professionals, indicating that volunteer data could be used to support professional monitoring programmes.