“We can quantify how different the results would be in real events,” de Guzman said. “I know that the number of extreme heat days is expected to be higher in each of these communities.”
In other words: It’s time to act. Tall trees provide shade, but plants generally give off water vapor when they photosynthesize, essentially “sweating.” Accordingly, a high-income neighborhood with lots of parks and landscaping can be up to 15 degrees Fahrenheit cooler than a low-income, more industrialized area—like so many health threats, Temperatures disproportionately affect the most deprived. The urban heat island effect not only varies from neighborhood to neighborhood, but also from block to block and even from house to house. Different building materials, such as wood and brick, absorb and retain solar energy in different ways.
So the utility of this type of research is to first find entire neighborhoods to prioritize for greening, and then target specific locations for individual tree placement. “We don’t necessarily need to plant entire forests in urban areas, just one tree at a time,” said Vivek Shandas, a climate adaptation scientist at Portland State University. Study the heat island effect but did not participate in the new study. “If you have limited funds and you know where the highest impact will be from implementing this feature, then identifying those locations is a no-brainer.”
But it’s not as easy as just sticking a bunch of plants in the ground and calling it a day. LA has embarked on a multi-year journey Urban forest management plan to increase tree canopy, especially in the most vulnerable areas. The agency must carefully identify locations to plant more trees, and must collaborate with the people there—for example, holding community feedback meetings. Some people may not want trees outside their homes: Maybe a branch once fell on their car, or their sidewalk cracked from the roots underneath, reducing his ability to move around. She sits in a wheelchair.
So having more trees in the urban landscape also means collaboration and education, helping people understand the significant cooling benefits that can save their lives—and at the very least reduce emissions. Single air conditioner. “If you have a negative story about trees, we have to provide some education to do better in the future,” said Rachel Malarich, Los Angeles City Forestry Officer. “The way we’ve learned as an industry is to be more selective about what we put where and match it to the location or change the location so we can grow something bigger .” For example, if a given patch of land is too small to fit a tree species large enough to provide shade, perhaps the city could redo the sidewalk to accommodate, while also improving mobility. And local temperature reduction.
In LA and elsewhere, scientists is urgently looking for plants it will be able to withstand temperatures 10, 15, 20 years from now—you wouldn’t want to plant a tree only to find out it can’t survive in the new climate. Climate change can also spread pests and diseases on trees, adding uncertainty to urban greenery: A given community may be interested in planting more tree species typical of their neighborhood —your magnolia or other idiosyncratic trees—but the future may become increasingly hostile to It.
