Vegetation cover change during a multi-year drought in Los Angeles
David L. Miller, Erin B. Wetherley, Dar A. Roberts, C. Tague, J. P. McFadden
Abstract
Vegetation in urban areas can provide many ecosystem services, such as cooler temperatures. In water-limited climates, maintaining benefits from vegetation during droughts requires significant water inputs and can be challenging due to the uneven effects of drought on vegetation. Here, we tracked changes in vegetation cover in Los Angeles, California using airborne hyperspectral imagery acquired annually from 2013 to 2018 and coinciding with the exceptional 2012–2016 California drought. Subpixel fractions for trees, turfgrass, non-photosynthetic vegetation (NPV; e.g., senesced plant material), and non-vegetated urban surfaces were mapped at 18 m spatial resolution using Multiple Endmember Spectral Mixture Analysis. We quantified cover changes through time, comparing how different physiographic regions of the city experienced vegetation change and assessing changes based on income and outdoor water use. From 2013 to 2018, overall turfgrass cover decreased (−17%) and NPV cover increased (+22%). Tree cover was more stable but decreased in 2018 (−6%). The inland valleys consistently lost more turfgrass than coastal areas. Higher income and water use areas had larger absolute changes in vegetation cover, likely due to their higher baseline of vegetation cover.