When is it Spring? Scientists Map Seasonal Greening with ForWarn

When will it be spring in your neck of the woods? That's a good question and now, you may be able to check with a simple map. Scientists have created a system that tracks the median "greenup" dates for natural vegetation to help land managers anticipate and plan for the impacts of disturbances.

Using the assessment tool ForWarn, researchers can monitor the growth and development of vegetation that signals winter's end and the awakening of a new growing season. Forwarn represents a way to more precisely characterize the beginning of seasonal greening, known as greenup, and compare its timing with that of the 14 previous years.

"In contrast to field observations that track leaf emergence for particular species of trees or herbaceous plants, ForWarn's LSP maps capture the response of the mixture of vegetation that can be seen from space," said William Hargrove, one of the researchers, in a news release.

The researchers used nationwide satellite imagery collected between 2000 and 2013 in order to quantify the seasonal progression from dormancy to peak greenness using a common scale from 0 to 100 percent. Then, the scientists picked the median date 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.

"The start of the annual growing season is among the most important climate-sensitive measurements that ForWarn can provide," said Steve Norman, one of the researchers. "Just as gardeners look to climate data to determine the typical last frost date, the typical greenup dates provides a baseline for land managers to establish expectations for seasonal duration and productivity."

The researchers have released three maps detailing the greenup in forests and grasslands, agricultural lands and urban areas.

To learn more about ForWarn, you can visit its website.

Want to see the maps for yourself? You can check them out here.

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