Trees vital as heat waves ravage Southland, experts and L.A. officials say


Los Angeles officials are working to preserve one of the city’s best – and most threatened – defenses against ever-increasing summer temperatures.

According to Mayor Eric Garcetti’s associate director of infrastructure, Jennifer McDowell, Los Angeles streets and sidewalks are home to 637, 275 trees. The number of total trees, including those at residences and parks, is estimated to be more than 10 million. The trees provide shade, and keep residents cool when water evaporates from its leaves.

That’s why officials are worried about shrinking green space in Los Angeles. According to a 2017 study by the University of Southern California, green cover for single-family home lots declined anywhere from 14 to 55 percent across the Southland. Despite city efforts, hundreds of trees have been cut down amidst development projects and infrastructural repairs.

No Green is a Red Flag

Yujuan Chen, a senior manager of urban forestry policy at advocacy group TreePeople, said that the loss of L.A.’s urban forest could have dire consequences for residents. Not only does green space keep the city cool, but trees can also have a positive effect on physical and mental health.

“People need trees, especially in the cities,” Chen said. “When people have more urban green spaces, you’ll feel happier and be healthier.”

But when trees are removed, communities suffer, especially underserved and impoverished communities in the inner city. A 2016 study published in the International Journal of Environmental Research and Public Health found that health-related quality of life was positively correlated with larger green spaces and tree canopies among Hispanic children in Houston, Texas. Another study in 2011 by the City University of New York School of Public Health found that more trees meant lower asthma rates.

The benefits are so comprehensive that Rob McDonald, lead scientist for The Nature Conservancy, suggested that cities should treat forestry as part of health mandates, especially when it comes time to fund urban forests.

“Communication and coordination between a city’s parks, forestry and public health departments is rare,” McDonald wrote. “Breaking down these silos can reveal new sources of funding for tree planting and maintenance.”

Development, or Destruction?

Despite these findings, Los Angeles has lost significant portions of its tree cover.

Areas such as South Los Angeles and San Pedro now have between 5 and 10 percent tree cover by area, whereas, in 2000, they had up to 30 percent tree cover, according to the 2017 USC study. Only L.A. Council District Four has more than 30 percent coverage now.

Cities around Los Angeles have not fared better, with Hawthorne, Baldwin Park and Pomona all seeing record deforestation. Of the cities analyzed in depth, only Pasadena kept more than 40 percent of its land area covered by trees.

According to Travis Longcore of USC’s Spatial Sciences Institute, who co-authored the study, development is partly to blame. In June, he told Curbed Los Angeles that lax regulations have made it easier for developers to pay fees for tree removal, rather than soak replacement costs.

“So you remove a tree—which provides a much greater annual economic value to the public—and then you don’t replace it?” Longcore said. “We are incentivizing people to remove them instead of working around them.”

However, McDowell said that climate change is also driving forestry patterns. Many of Southern California’s trees are non-native to the region and, with temperatures on the rise, drought-resistance will have to factor into future forestry efforts.

“We’re definitely looking very closely at those issues,” McDowell said. “We want to make our urban forest more drought resistant.”

Forestry of the Future

Researchers with the University of California Cooperative Extension are helping do just that. In partnership with the United States Forest Service, researchers there have launched a 20-year study to identify trees that can withstand higher temperatures and lower rainfall. Native trees such as the Catalina Cherry and Ironwood trees, along with imports like Ghost Gum and Acacia trees, could form the future of L.A.’s canopy.

Additionally, McDowell said the City of Los Angeles is currently in the process of hiring an urban forest administrator who will coordinate re-forestry efforts across the city.

After all, Chen said, such efforts will be vital to the future of Los Angeles, as climate change has only just begun.

“The trees can be nature’s air conditioner,” Chen said.


  1. Removing “green” areas around homes and replacing with stones, crushed rock, cement, bricks, and other non living matter raises temperatures around our homes.


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