Climate Change is Intensifying Drought in Southern California

Caitlin Dempsey

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Normalized difference vegetation index satellite images of the state before and during the drought. | Image courtesy Chunyu Dong/UCLA.

A team of researchers from UCLA and Columbia University have found that the most recent 2012–16 drought had a greater impact on Southern California than it did in parts of the state to the north.

Glen MacDonald, a UCLA climate scientist and one of the co-authors of the paper published in Geophysical Research Letters noted, “Southern California is more prone than the northern part of the state to getting severe droughts, but that difference seems to be increasing.”

The study analyzed changes in normalized difference vegetation index (NDVI) which is a calculation of vegetation greenness from satellite data.  The health of vegetation, as measured in greenness, can be measured by calculating  the ratio of visible light absorbed and near-infrared light reflected by those plants.

Picture of dead and dying conifer trees in California, October 16, 2015.
Dead trees viewed from the Colony Mill Trail in Sequoia National Park, photographed in 2015 during severe drought in California.. Photo: Nathan Stephenson, USGS . Public domain, October 16, 2015.

As vegetation becomes stressed by increased heat and drought, greenness declines.  As climate exacerbates drought conditions, particularly in Southern California, satellite data has been able to captured the decline in the normalized difference vegetation index (NDVI).

Normalized difference vegetation index satellite images of the state before and during the drought. | Image courtesy Chunyu Dong/UCLA.
Normalized difference vegetation index satellite images of the state before and during the drought. | Image courtesy Chunyu Dong/UCLA.

The study

Dong, C., MacDonald, G. M., Willis, K., Gillespie, T. W., Okin, G. S., & Williams, A. P. (2019). Vegetation Responses to 2012‐2016 Drought in Northern and Southern CaliforniaGeophysical Research Letters.





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Caitlin Dempsey

Caitlin Dempsey is a geographer, writer, and founder and editor of Geography Realm. She holds bachelor's and master's degrees in Geography from UCLA and a Master of Library and Information Science (MLIS) from San José State University.

For more than two decades, she has written about geography, maps, geographic information systems (GIS), remote sensing, satellite imagery, and environmental science. Her work focuses on making geography accessible to a broad audience through articles, tutorials, and educational resources.

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