PROJECTS
Evaluating impacts of trees on residential thermal conditions using community science
Heat-health risk can be mitigated by trees, but there are critical gaps in knowledge that Dr. Alan Barreca and I investigated through an empirical study funded by Accelerate Resilience L.A. We engaged residents in southeast Los Angeles County to host sensors in their homes during the COVID-19 pandemic. Participants contributed continuous half-hourly readings for indoor (bedroom and living room) and outdoor (eave) temperatures for a period of 11 weeks, including the hottest day ever recorded in Los Angeles County.
On average, we found that indoor temperatures in treehouses warm 1.1°F less on hot days compared to non-treehouses. If homes in heat-vulnerable parts of Los Angeles were 1°F cooler we could reduce heat-related deaths by 10-20%, and with additional tree canopy and solar reflectance increases the number of lives saved could grow to 30% or more. However, we also find that trees provide relatively less benefit at night, a finding that is consistent with other studies but warrants further investigation for its potential impact on public health.
Rx for hot cities: Climate resilience through urban greening and cooling
Extreme heat causes more deaths in the United States than all other weather-related causes combined. In Los Angeles, the groups expected to see the largest increases in mortality as the climate warms are elderly, Black , and Latinx communities.
To address this, Dr. Larry Kalkstein and I co-founded the Los Angeles Urban Cooling Collaborative, a multi-disciplinary, national partnership of researchers and expert practitioners working with communities, nonprofit organizations, academia, and government toward the goal of understanding and implementing urban cooling strategies.
Our research found that roughly one in four lives currently lost during heat waves could be saved, largely in low-income communities and communities of color. We also found that climate change-induced warming could be delayed approximately 25 to 60 years under business-as-usual and moderate mitigation scenarios, respectively. Project funded by the USDA Forest Service and Harvard-Westlake School.
Closing the urban forest equity gap in Los Angeles
The systemic lack of green spaces in lower income communities and communities of color links to disproportionate exposure to extreme heat, poor air quality, and related public health risks. In many neighborhoods, race-based historical planning decisions invested in parks and street trees within whiter and wealthier areas, creating environmental injustices elsewhere in the city.
Working closely with City Plants and CAPA Strategies, in 2020 we co-founded the LA Urban Forest Equity Collective, with funding from Accelerate Resilience Los Angeles, the LA Center for Urban Natural Resources Sustainability, and the US Forest Service. We are assessing urban forest equity conditions, developing a tiered planting process to create a pathway for planting in densely-populated neighborhoods that have limited space, and developing a framework to dismantle the physical, political, and social barriers that perpetuate urban forest inequity.
Check out the equity assessment report, design guidebook, and infographic from phase 1.
Fostering tree stewardship and community resilience
Providing establishment-period care to young trees is a challenge to increasing urban forest equity -- particularly in arid and semi-arid regions like Los Angeles. This study sought to produce a replicable approach to engaging residents in environmental justice communities to actively care for young street trees planted in front of their homes. Using Community-Based Social Marketing in the community of Huntington Park (Los Angeles County, California), we investigated socioeconomic and cultural characteristics to barriers and motivators around tree stewardship and developed an outreach program strategy accordingly. We then pilot-tested and evaluated the program for effectiveness in changing behavior, testing active, in-person engagement against more passive outreach, where program materials were left at the doorstep. Project funded by the L.A. Center for Urban Natural Resources Sustainability.
Building off of this project, we are expanding the research scope into the City of San Fernando to determine whether environmental stewardship programs can be an effective portal to increase heat-risk awareness and boost community resilience to a variety of stressors. Project funded by the California Department of Forestry and Fire Protection.
Read the article in the Journal of Arboriculture and Urban Forestry.
Stormwater solutions for Los Angeles
The City of Los Angeles’ first-ever Stormwater Capture Master Plan looks at existing stormwater capture and quantifies how to maximize its potential as a way to reduce reliance on imported water. The Plan process was initiated by my colleague Deborah Bloome, and she and I served as advisors to the Los Angeles Department of Water and Power staff and consulting engineers — an unusual role for an NGO representative to have. We used research-based advocacy to ensure inclusion of progressive targets and approaches, helping create a more ambitious and sustainable vision for LA’s water future that prioritizes local sources.
To demonstrate what this water future might take shape, our team founded and facilitated the Greater LA Water Collaborative — a collaborative governance partnership among LADWP, LA City Bureau of Sanitation, and the LA County Department of Public works. We co-designed and retrofitted pilot homes with large rainwater cisterns and rain gardens to demonstrate how Angelenos can secure a climate-resilient future by capturing stormwater at home.
This project, dubbed StormCatcher, features high-tech rainwater management systems equipped with cloud-based monitoring and controls to optimize system performance in real time.
Read more about the Stormwater Capture Master Plan.
Read more about the Greater LA Water Collaborative and the StormCatcher project.
Transferring lessons to California from Australia’s Millennium Drought
Southern California and Southern Australia are two regions of the world which share many climatic, socioeconomic and demographic characteristics that lend themselves to meaningful exchanges of knowledge and innovations. With the benefit of Australia’s documented experiences, California can learn what solutions worked and did not work in Australia, potentially avoiding major pitfalls.
I co-led two study tours to Australia in 2012, meeting with water management and planning entities in Australia’s five largest cities. Based on this research, in 2014, TreePeople and The Energy Coalition co-organized and led a delegation of policymakers and elected officials from California to Melbourne and Adelaide. The delegation produced changes in the regulation of non-potable water and in planning for extreme heat mitigation in Los Angeles.
Greening plan for Inglewood & Lennox
Working closely with Social Justice Learning Institute, over four years our small but mighty team facilitated participants representing dozens of community, government, and nonprofit entities to develop a collective vision and set of goals to advance environmental and social justice in Inglewood and Lennox.
We focused on creating an intentional, replicable model by using non-traditional planning processes grounded in non-hierarchical communication practices. What emerged was a comprehensive and actionable community vision that will help protect and enhance the urban forest, urban cooling, air and water quality, and local water supply to make these communities resilient to climate change.
Read the Vibrant Cities Lab case study about the greening plan.
Tree canopy assessment and map viewer for Los Angeles County
Managing the urban forest requires accurate spatial data — data which has long been unavailable for our region. In partnership with Dr. Michele Romolini and the Center for Urban Resilience (Loyola Marymount University), this project produced a LiDAR-based high-resolution assessment of L.A. County’s existing and potential tree canopy cover. Our team engaged the Consulting Group at SavATree and the University of Vermont Spatial Analysis Lab to help us look at the spatial distribution of green infrastructure in Los Angeles.
Using these data, and in collaboration with Dr. Shenyue Jia at the Center of Excellence in Earth Systems Modeling and Observations (Chapman University), we built a basic interactive viewer showing existing and possible tree canopy cover, and an advanced viewer showing detailed land cover maps at multiple scales.
Explore the tree canopy assessment report, presentations, and videos.