California’s Urban Schools: A Shade-Deprived Environment
The vast majority of urban, public grade schools in California are paved-over “nature deserts” sorely lacking in trees or shade, leaving most of the state’s 5.8 million school-age children to bake in the sun during breaks from the classroom as rising global temperatures usher in more dangerous heat waves. This concerning reality is the conclusion of a team of California researchers from UCLA, UC Davis, and UC Berkeley, who studied changes in tree cover at 7,262 urban public schools across the Golden State between 2018 and 2022.
The ongoing joint project, which drew from urban tree canopy maps developed by study partners the California Department of Forestry and Fire Protection and the U.S. Forest Service, revealed that 85% of the schools lost about 1.8% of tree cover on average in that four-year span. The situation appears to be just as worrisome today, the team said. Kirsten Schwarz, the research lead at UCLA, emphasized that “extreme heat is becoming a major public health concern in California and across the country, and trees can play a really big role in helping us cool down those schools and also build climate resilience.”
Tree Cover and Heat Measurements
The researchers collaborated with the nonprofit Green Schoolyards America, which found in its own 2024 study that California’s public K-12 schoolyards have a median tree cover of just 6.4%. More than half of that canopy exists only as decoration at school entrances, in parking lots, and along campus perimeters. The team conducted new field research in a subset of schools, including some in Southern California, the Bay Area, and the Central Valley, to gather more detailed data on tree cover and heat measurements.
Accompanying the UCLA researchers to a selection of schools in each district were researchers from UC Davis, who took heat measurements using portable weather stations and sensors. They captured thermal images, air temperatures, and humidity around different paving materials, such as grass, mulch, turf, rubber, and concrete, to examine the microclimates specific to those campuses over an extended span. Alessandro Ossola, an urban plant scientist leading the UC Davis team, stressed that children spend a significant amount of time at school and are more vulnerable to extreme heat due to their smaller stature and underdeveloped ability to regulate body temperature.
Barriers to Schoolyard Greening
Despite the importance of tree cover and shade, many obstacles hinder efforts to make campuses more hospitable. Schwarz cited a 2024 policy report by her UCLA team, which examined the greening of inadequately shaded schools and policies that make it difficult to carry out improvements. The report highlighted a lack of staffing, bureaucratic hurdles, state seismic safety standards, and funding models that prioritize low-maintenance campuses as significant barriers to schoolyard greening.
Schwarz also noted that regulations requiring non-grass surfaces for sports and outdoor physical education can dictate the design of some schoolyards, while other schools must choose between conflicting long-term priorities, such as plans for future construction of additional classrooms versus creating shadier open spaces. The tree canopy researchers plan to present each participating school with a tree inventory, analysis of findings, policy recommendations, and suggestions for incorporating their study into classroom lessons and parent outreach.
A Call to Action
The researchers’ main motivation in initiating the study was to help communities maximize the benefits of $150 million in Cal Fire grants approved by the state Legislature, which schools can apply for to plant grass and trees on their campuses and reduce the harm of heat-radiating surfaces such as asphalt. Ossola emphasized that Californians who want to improve their children’s schoolyards are playing catchup, even with community will and funding sources in place, as it can take decades for young trees planted today to mature enough to provide the necessary cooling effects.
For more information on this critical issue, read the full report Here.
Image Source: www.latimes.com
