Advances in imaging technology are helping scientists understand how trees respond to climate change. High-resolution images taken by cubesats, small devices launched into orbit, are making it possible to study both the entire forest and individual trees. In Washington D.C., new research by Prof. Michael Alonzo raises questions about the role of heat in the early onset of urban forest growing seasons. Previous studies using pixelated satellite images suggested that urban heat advanced the “green up” of trees, but Alonzo’s work with cubesat imagery challenges this understanding.
The urban heat island effect, where cities are hotter than nonurban areas, is often cited as the reason for longer growing seasons in cities. However, Alonzo suggests that the importance of urban heat may be overstated. Pixelated images from satellites do not allow scientists to study different species individually, and the technology does not provide daily imagery. Cubesat imagery, on the other hand, allows for the monitoring of continuous changes, such as the development of leaves during the growing season.
Alonzo and his colleagues analyzed cubesat imagery of tree crowns in Washington, D.C., from 2018 to 2020. They monitored the timing of green up and leaf loss for each tree and considered factors like species, planting location, air temperature, and impervious surface cover. The findings of the study have implications for urban and nonurban areas and different types of trees.
Cubesats are not only used by NASA or the private space industry, but also by a small group of scientists studying trees. Alonzo uses various tools, including drones and satellites, to analyze tree health. In the future, he plans to use cubesat imagery to monitor agricultural activity in Nigeria and forest changes in Haiti, collaborating with professors in the School of International Service.
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