Researchers Map Seasonal Greening in U.S. Forests, Fields, and Urban Areas
In contrast to field observations that track leaf emergence for particular species of trees or herbaceous plants with each new growing season, the ForWarn tool captures the response of the actual mixture of vegetation that can be seen from space. Just prior to the beginning of the 2015 growing season, ForWarn researchers from the Eastern Threat Center released three maps detailing the start of seasonal greening, or “greenup,” in forests and grasslands, agricultural lands, and urban areas. The maps were featured as news items in more than 40 media outlets.
To develop the maps, researchers used nationwide satellite imagery collected between 2000 and 2013 to quantify the seasonal progression from dormancy to peak greenness using a common scale from 0 to 100 percent, and then picked the median date over those 14 years that was associated with 20 percent greenup at each location as a common reference point signaling a clear launch of the growing season. The maps’ median greenup dates are particularly useful for managers of mainly deciduous forests, grasslands, and crops; knowing more precisely the onset and timing of spring green-up allows for earlier detection and recognition of disturbances such as those from wind, hail, frost, and fire, and allows earlier recognition of pests such as defoliating insects that become active when leaves appear. The greenup maps and other weekly maps that can help users track the growth and development of vegetation throughout the growing season are available via ForWarn’s recently upgraded Forest Change Assessment Viewer, which can also be viewed on smart phones and tablets.
Right: A ForWarn map shows the median greenup dates across all lands to help land managers anticipate and plan for the impacts of disturbances. Click to enlarge.
Forest Service Partners/Collaborators: Western Wildland Environmental Threat Assessment Center
External Partners/Collaborators: NASA Stennis Space Center; Department of Energy Oak Ridge National Laboratory; University of North Carolina Asheville National Environmental Modeling and Analysis Center; U.S. Geological Survey Earth Resources Observation and Science Center
Contact: William Hargrove
