Drought and Vegetation

About this map

While many California native plants are adapted to the region’s dry Mediterranean climate, long periods of intense drought (like the 2012-2016 California drought) can have a significant impact on native vegetation. This map shows how vegetation greenness was affected by drought from 2000-2017: dark red indicates highly affected areas, while less impacted areas are shown in blue.

In the Los Angeles region, you can see pronounced effects in coastal mountain ranges (e.g. the Santa Monica mountains) and other areas with chaparral vegetation. Chaparral is a common vegetation type in Southern California that includes evergreen shrubs with deep roots and tough leaves—characteristics that allow plants to survive drought conditions. However, chaparral is extremely vulnerable to the combination of prolonged drought and extreme temperatures.

As temperatures continue to warm, California’s native plants (including endemic species that are found nowhere else in the world) are increasingly at risk of losing suitable habitat.

About this Map

In order to study how vegetation responds to drought, researchers compared the normalized difference vegetation index, or NDVI (a measure of greenness), to the Palmer Drought Severity Index, PDSI (a measure of how intense a drought is) from February 2000 to April 2017. White/blank areas in the study extent indicate an insignificant relationship between NDVI and PDSI or data gaps due to snow or cloud cover.

Data source: NDVI-PDSI layer derived from Dong et al. (2019) in Remote Sensing 11(24) [link]. Burned area layer derived from CA FIRE FRAP, Fire Perimeters, updated May 2020. Fire hazard data from California Department of Forestry and Fire Protection. Retrieved from frap.fire.ca.gov.

Acknowledgements: We would like to thank Chunyu Dong for sharing this NDVI-drought research.