Most of us have heard the timeless proverb, "The best time to plant a tree was 20 years ago. The second best time is now.” Worldwide, there is growing discussion in cities about planting more trees as policymakers and neighbors look to increase shade on warming city streets.

Extreme temperatures are becoming more common in cities where concrete and infrastructure are now creating heat islands—areas that experience higher temperatures, leading to poor air quality, dehydration and other public health concerns. Trees are increasingly seen as a solution to both lowering street-level temperatures while improving quality of life. Yet many cities may not have the budget or resources to locate where every tree in town is, or where new tree-planting efforts are most needed.

With our new Tree Canopy Lab we are combining AI and aerial imagery to help cities see their current tree canopy coverage and plan future tree planting projects, starting with the City of Los Angeles. 

With the Tree Canopy Lab you can see Los Angeles’s trees with local context, like what percentage of a neighborhood has leafy cover, an area’s population density, what areas are vulnerable to extreme heat, and which neighborhood councils can help get new roots in the ground.

Tree Canopy lab is in our Environmental Insights Explorer platform, a tool that makes it easier for cities to measure, plan and reduce carbon emissions and pollution. It’s also one step forward in part our commitment to help hundreds of local governments fight climate change.

Mapping tree cover to seed new urban forestry efforts

With aerial imagery collected from planes during the spring, summer and fall seasons, as well as Google AI and Google Earth Engine’s data analysis capabilities, we can now pinpoint all the trees in a city and measure their density. The imagery we use for these calculations includes color photos that closely represent how we would see a city from the sky. To get even more detailed information about the city’s canopy cover, near-infrared photos detect colors and details that human eyes can’t see and compare images from different angles to create a height map.

We then use a specialized tree-detection AI that automatically scans the images, detects the presence of trees and then produces a map that shows the density of tree cover, also known as “tree canopy.” 

With this tool, the City of Los Angeles doesn’t have to rely on expensive and time-intensive manual tree studies which can involve block-by-block tree surveys, outdated records, or incomplete studies which only count trees in public spaces.

From policymakers to neighbors, anyone can explore Los Angeles in the Tree Canopy Lab and glean insights. For example, the lab can help anyone identify residential blocks with high tree planting potential and locate sidewalks that are vulnerable to higher temperatures due to low canopy coverage.

With Tree Canopy Lab we’ve found that more than 50 percent of Angelenos live in areas with less than 10 percent tree canopy coverage and 44 percent of Angelenos live in areas with extreme heat risk. We also see a correlation that shows parts of Los Angeles with the lowest heat risk also have the highest tree canopy coverage — these areas are also the lowest population density of Angelenos.

Connecting cities with new environmental insights

Los Angeles has been on the forefront of cities using urban forestry to not only advance sustainability goals, but to beautify neighborhoods, improve air quality and bring down street-level temperatures as the region gets hotter due to climate change.

With a near-term goal of planting and maintaining 90,000 trees by 2021 and continuing to plant trees at a rate of 20,000 per year across a city of more than 503 square miles, the Tree Canopy Lab is already helping people across the city reach this goal. From neighbors and community organizations to Mayor Eric Garcetti and the city’s first-ever forestry officer, Rachel Malarich, they all have access to a birds-eye view of where the city’s existing trees are and which areas need more greenery. 

“Every tree we plant can help stem the tide of the climate crisis, and when we expand our urban forest, we can sow the seeds of a healthier, more sustainable and equitable future for communities hit hardest by rising temperatures and intensifying heat waves. Google’s technology will help us bring the power of trees to families and households across Los Angeles -- adding greenery to our public spaces, injecting beauty into our city, and bringing cooler temperatures to our neighborhoods.” 

-Mayor of Los Angeles, Eric Garcetti

More tree insights for more cities on the horizon

We’ll be making the insights in Tree Canopy Lab available to hundreds of more cities in the year to come as we continue to support the ambitious work cities like Los Angeles are doing to embark on tree planting and maintenance initiatives.