Biologists. land managers. and policy makers increasingly utilize volunteer-generated data to supplcmenl their own data collection efforts and to identify hahitat dsgradztion or land management stratepie?. However, many professionals who muld potentially benefit from valuntcel- dafs are con- cerned about the quality of such data. This study examined forest data from one of the largest vahcnteer monitoring programs in the Midwestern United States. Ulinois EcoWatch Network recrulls volunteers lo collect statewide trend dara on the lhahitat quality ol' forests hy monitoring strucrural dynamics (changcs in the dominant trcc spccies) and the density and spread of scvcn invasive shrub species known to adversely impact native flora. In order to asscss the accuracy of volunteer data collection efforts. botitnists collected parallel data at 14 sites fix comparison to volunteer sampling of tree and shrub iJentilicatir>n, abundance. and size class placements. We fol~nd no sipniticant difference lor 12 out of 20 species identilied by volunteers at thesc sites (P> 0.05). Volunteer accuracy rates tbr I? (om of 1.51 tree genera were 80% or higher. However, spccies within the Ulnlr,s and Qrtrrcus genera presented greater difficulty la the volunteers. We also detcctcd large discrepancies in the shruh survey counts or highly ahundant species such as Riber nzi.~sotmricnse Nutt In spite OF these discrepancies. we suggest the data can provide valuahle informittion for measuring lone-term changes in forest hnhilat quality. Improvements in data oollccti~~n mrthoda and training in cornbination with strat?*rs lo inrorm usen of potential dara limitations should enhance the usefulness of vulunteer-cullected data fb,r mmnst natural resource dccisioo-making processes.
