Seasonal phenological changes recorded at ground level in New Hampshire's Bartlett Experimental Forest (left image) and by satellite sensors for the northeastern U.S. and southeastern Canada (right image). Photographs courtesy of Dr. Andrew Richardson
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A Longstanding Tradition
Phenology is not a new science. The Chinese are credited with keeping the first written phenological records, which date back to nearly 1000 BC. In Japan, accounts of when cherry tree blossoms were at their peak each year have been maintained for the last twelve centuries. Swedish botanist Carolus Linnaeus and British landowner Robert Marsham both kept precise and systematic phenological records in the 1700s. Their work did much to shape modern phenological observations, which are today aided by internet technology. In the United Kingdom, for example, Nature's Calendar integrates over two million seasonal change sightings made by adults and schoolchildren each year. The USA National Phenology Network brings together citizen scientists, government agencies, educators and others to monitor the impacts of climate change on plants and animals across the U.S.
Remote Sensing Phenology - A Unique Perspective
Remote sensing phenology—the use of satellites to track phenological events—complements ground observation networks. Satellites provide a unique perspective of the planet and allow for regular, even daily, monitoring of the entire global land surface.
Because the most frequently used satellite sensors for monitoring phenological events have relatively large "footprints" on the land surface, they gather data about entire ecosystems or regions rather than individual species. Remote sensing phenology can reveal
broad-scale phenological trends that would be difficult, if not impossible, to detect from the ground. And, because data collection by satellite sensors can be standardized, the data are reliably objective. Remotely sensed phenological data are useful for assessing crop conditions, drought severity, and wildfire risk as well as tracking invasive species, infectious diseases, and insect pests. Because phenological events are sensitive to climate variation, these data also represent a powerful tool for documenting phenological trends over time and detecting the impacts of climate change on ecosystems at multiple scales.