Tree canopy change in coastal Los Angeles 2009-2014

Los Angeles, California is prone to extreme climate events—e.g. drought, wildfires, and floods—that are only expected to increase with climate change. The establishment of green infrastructure, including a stable urban forest, is a strategy to improve resilience not only to these events, but also to contribute to other environmental, social, and economic goals. To this end, cities throughout Los Angeles County have tree planting programs and policies aimed to grow and maintain their urban forests. Despite the policy objectives and management goals of such programs, we know surprisingly little about the spatial distribution of the existing urban forest, how and where the canopy has changed over time, or the composition of the population living in places of canopy change. To examine these questions, we conducted an analysis of the Los Angeles Coast based on land cover data derived from high-resolution aerial imagery and LiDAR. In addition to characterizing the overall percentages of existing and possible tree canopy in 2014, we also characterized the change in tree canopy from 2009 to 2014 with five measures of tree canopy and change: total canopy, persistence, loss, gain, and net change. We used market segmentation data to analyze the relationship between tree canopy and the composition of communities. Results indicated that tree canopy covered about 15% of coastal Los Angeles, but this cover was unevenly distributed throughout the study area. The parcel-level analysis of change indicated that while the canopy did not change much from 2009-2014, the changes that did occur were localized and would have been missed at a coarser scale of analysis. Using geodemographic segments, we found that higher-income lifestyle groups tended to have more tree canopy and less loss over time. Change within land uses was consistent with overall change. These high-resolution, high-accuracy data and analyses can support valuable tools to guide decision-making about urban forests, especially as it relates to social equity.