Global Learning and Observations to Benefit the Environment (GLOBE) is an international science and education program for primary and secondary students with 112 participating countries and more than 50000 GLOBE-trained teachers representing over 20000 schools. GLOBE’s mission is to promote the teaching and learning of science, enhance environmental literacy and stewardship, and promote scientific discovery. Students engage in research investigations on atmosphere, hydrology, soils, land cover and/or phenology at their schools, in collaboration with teachers, scientists, and community members. GLOBE students have used scientifically standardized methods and contributed more than 20 million  measurements to the GLOBE database. Since 1999, GLOBE students from more than 300 schools around the world have made over 200,000 phenology measurements at their schools. This data set, largely untapped for scientific purposes could provide a means of field validation of satellite-derived phenology data. 

Results/Conclusions

GLOBE, Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) data were used in monitoring start of season (SOS) in Alaska. Results indicated differing processing and spectral characteristics of AVHRR and MODIS sensors restrict continuity between the normalized difference vegetation index (NDVI) datasets for Fairbanks, Alaska. The AVHRR and MODIS regression models resulted in significantly different NDVI curves and subsequently different start, peak and length of growing seasons in three land cover groups. NDVI, while useful for its spatial coverage, has limitations in boreal regions due to snow, the large extent of conifers, and clouds which restrict the composite period.  

In collaboration with the GLOBE program, students measured urbanization effect on leaf budburst timing in native deciduous trees in seven cities in Asia, Europe, Africa and North America. Using Landsat satellite imagery from each city, sites within each study area were classified as rural or urban, and land surface temperature (LST), vegetation fractional cover (Fr), and impervious surface area calculated. Timing of budburst, measured by students using GLOBE protocols, was statistically different within all cities. Only one city followed the classic urban phenology paradigm, which proposes higher LST, lower Fr, and earlier budburst in urban areas. Urban budburst was earlier in three of four temperate cities but in only one of three tropical cities. Results suggest that while vegetation phenology is consistently different between urban and rural areas, a consistent paradigm based on the explanatory variables in this study did not emerge.

GLOBE student data have proven useful in phenological studies and would similarly be useful to climate change studies.