We’re working to understand which trees provide more cooling to Los Angeles and minimize water loss.

The Earthwatch Urban Resiliency Program is characterizing the variation in growth, ecosystem services, and water use associated with different tree species in various micro-climates throughout the greater Los Angeles metropolitan region.

We’re assessing the current extent and condition of urban forests within Southern California, and refining priority areas for future tree plantings and maintenance. The data we are collecting will help:

  • Develop tree management plans by identifying which trees will grow best in LA over the next 50 years with increasing climate change.
  • Guide improved investment in the right green infrastructure by increasing the confidence by managers in assessments of biomass, CO2 stored, annual CO2 sequestration, and emissions avoided due to urban forests.
  • Report on a range of environmental benefits including heat island mitigation and cooling for humans and buildings.
  • Determine priority areas for tree planting using tree canopy and impervious data, as well as updated demographic, climate, and air pollution data.

Why the science is important

Trees in cities provide a large number of benefits, such as improved human health and well-being, and wildlife habitat. Choosing where, which, and how many trees to plant and steward depends on the motivations of many people, but also on our understanding and confidence in the benefits they provide. Many of these benefits can be quantified in dollars. The economic models depend on accurate knowledge of how trees are growing, using water, and surviving, as well as how they are being impacted by threats including drought, pollution, emerging pests and diseases, soil compaction, and shading by buildings. By gaining an improved understanding of the value of urban forests and threats to them, we can provide local tree managers, policy makers, and the general public with new tools to make better decisions on which trees to plant where.

Geographic focus of the program

Since August 2014, the program has grown out of five centers: Los Angeles, Long Beach, San Gabriel Valley, Riverside, and Palm Springs. These communities were strategically chosen based on their ability to invest in green spaces, and/or the need to build resiliency to climate change.  In Southern California, where the number of extreme heat days is projected to be greater than 30 each year, there is an acute need for research on urban resiliency and climate change mitigation.

The LA Urban Area contains species of trees from almost every global biome across a comparatively small yet dramatic climate gradient. Because of this, we are able to examine the diversity of growing strategies, and the flexibility and adaptability of each species across changes in climate. To date, we have collected data from over 40 parks and green space across the region, involving over 600 people to collect data on over 1,200 trees.

Study Region Map




The four study regions of Resilient Trees 2.0

Operation Resilient Trees (July 2015 – present)

During Resilient Trees 1.0 (July 2015-May 2016), citizen scientists collected measurements on 10 different tree species across a 150 mile-long geographical gradient in order to better understand each species’ water use, cooling benefit, and physiological performance in each climate zone.  Resilient Trees 2.0 (July-December 2016) continued this work with almost 400 tree measurements on a new set of 10 species.  Resilient Trees 3.0 (January-June 2017) will focus on another set of 10 species, culminating in valuable research on 30 species of urban trees that are potentially “climate-ready.”


Operation Tree Canopy (August 2014-2015)

Citizen scientists collected on-the-ground data to corroborate NASA aerial imagery of the study region. Recording tree species, health, size, and taking a physical sample of each tree’s leaves, citizen scientists provided essential ground-truthing for the climate, land cover, and temperature models being developed from NASA’s data.

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