According to scientific studies, spring is beginning earlier due to climate change. We can help scientists research this issue by collecting data about when trees sprout their leaves across Europe. In this project, students will select tree species that grow in the regions where their schools are located, identify specimens of those species in their school grounds or close to them, observe when they sprout their leaves in spring, and record their observations on the citizen science app called iNaturalist. In line with UN’s Sustainable Development Goals No. 4, 13, 15, and 17, through this project, students will contribute to research a real global problem, as iNaturalist shares the observations with scientists; they will realise that “ordinary” citizens can contribute to global issues; they will learn and reflect on the effects of climate change; and they will become aware of the differences between the North and the South of Europe regarding the arrival of spring.