Patterns in forest plant phenology: Can citizen scientists accurately assess phenological changes?

Background/Question/Methods

Phenology, the timing of life-cycle events and seasonal activities of organisms, is an area of study that is particularly relevant for scientists investigating the effects of global climate change. Currently, the ability to track phenological change is compromised by the lack of data across space and time. To ameliorate this lack, data gathered by citizen scientists is increasingly being used to track large and small-scale phenological trends across taxa.  Scientists’ ability to confidently analyze data collected by citizen scientists hinges upon demonstration that these data are reliable and accurate. Here, we employ the use of a citizen science initiative to evaluate accuracy and consistency in citizens’ observations along a “phenology trail” in a forested reserve in Portland, Or. Volunteers were trained in methods of plant and phenophase identification and encouraged to make observations once a week. Approximately 11,000 observations were recorded over the course of one field season by 28 citizen and student scientist volunteers and compared to observations made by a professional field ecologist to evaluate accuracy and consistency across observations and observers. 

Results/Conclusions

Preliminary analysis shows that volunteers consistently identified phenophases correctly (approximately 90% accurate) for the 19 different species observed. There was a slight improvement in observers’ accuracy over the course of the season, suggesting that observers improved their ability to correctly identify phenophases as they gained experience. Observers most frequently identified fruit phenophases correctly and showed the least accuracy identifying emerging leaves. Observer accuracy level further varied by functional type; accuracy was generally highest for forbs and shrubs and lowest for large trees where flowering and fruiting bodies were over observers’ heads. This level of fine-scale detail will aid in future program development for citizen scientist initiatives focused on plant phenology. Overall, these findings demonstrate the legitimacy of data collected by citizen and student science volunteers, an important finding for analysts relying on data collected by non-scientists, such as participants in the USA National Phenology Network’s Nature’s Notebook phenology observing program.