Over 2 years, across Miami-Dade, more than 9,000 trees reveal a hidden journey of heat: Mature canopies can pull temperatures down by 10°F, turning scorching streets into cooler urban spaces for residents

On a scorching Miami afternoon, a patch of shade can feel like an entirely different climate. Beneath a mature tree, the pavement feels less punishing and the heat becomes easier to escape. That cooling effect is at the center of research by Florida International University scientists, who have spent more than two years studying trees across Miami-Dade County.

Their work involving more than 9,000 urban trees suggests that trees are not simply part of a city's landscaping. Their size, species, location and canopy can make a meaningful difference to urban temperatures.

How much can trees cool Miami?

Miami-Dade recently experienced one of its longest stretches of consecutive 90-plus-degree days on record, with heat indices climbing above 100 degrees. In neighborhoods filled with asphalt, concrete and rooftops, the urban heat island effect can make those conditions feel even more intense.


FIU researchers found that trees can cool urban areas by as much as 10 degrees. But the cooling benefit is not the same for every tree.

Madison Kinder, an urban ecology fellow in FIU's Institute of Environment, is studying how trees affect communities, including their ability to reduce UV exposure. She notes that a young tree does not provide the same cooling effect as a large, older tree.

The research draws on more than two years of temperature monitoring, inventories covering more than 9,000 urban trees, countywide tree-canopy analysis and a survey of 600 residents. Together, the findings point to a simple but important distinction: planting trees is only part of the equation.

Which trees provide the most shade?

Trees with large, dense canopies, including native fig trees, provide greater cooling than palms and ornamental trees such as royal poinciana.

In Coconut Grove, Christopher Baraloto, director of the International Center for Tropical Botany at the Kampong, led a detailed inventory of street trees and found a remarkably diverse urban forest. Yet much of Miami's street-tree diversity comes from palms and other species that provide relatively limited canopy.

A smaller group of large trees, including native live oak and gumbo limbo, currently provides a disproportionate share of street-level canopy.

“A diverse urban forest is desirable, but diversity, tree numbers, and ecological function are not interchangeable,” Baraloto said. “Protecting existing large trees while selecting species capable of developing substantial crowns could matter as much as increasing the number of trees planted.”

For Baraloto, the issue is therefore not simply about increasing the number of trees. The type of tree and the canopy it can eventually develop matter just as much.

Why does protecting mature canopy matter?

Miami-Dade had about 20 percent tree canopy coverage based on 2022 data from FIU's Geographic Information Systems Center. That remains below the 30 percent goal established by county officials.

Jennifer Fu, director of the FIU Coastal Environmental Data and GIS Center, said an updated assessment is urgently needed to understand where the county's tree canopy is changing, how it is changing and why.

Baraloto has also been appointed to the City of Miami's Tree Ordinance Advisory Committee, which is reviewing tree preservation and protection regulations. The city is holding five community workshops for residents to ask questions and provide feedback.

The larger question is how development can be balanced with the need to maintain Miami's urban forest.

“I hope everyone can recognize the value of trees for their ecological benefits including cooling and stormwater mitigation,” Baraloto said. “If we start with that premise, I believe we can have the conversations needed to support healthy, vibrant communities.”

He also said Miami's existing trees are already helping residents cope with extreme heat, while stronger mitigation requirements, smarter species selection and targeted investment could help neighborhoods that need shade the most.

"Miami’s urban forest is already doing important work protecting residents from extreme heat, but what we need now are mitigation requirements that better reflect what is being lost, smarter species selection and targeted investment in neighborhoods that need shade the most."

The FIU research is being carried out with community organizations across Miami-Dade County and supported by the William R. Kenan, Jr. Charitable Trust, the Korth Family Foundation, the Dr. Michael and Diane Rosenberg Family Foundation, and a Florida Urban and Community Forestry grant from the U.S. Forest Service, as quoted by FIU News.

The findings summarized here are from research conducted by Florida International University researchers through the Institute of Environment and the International Center for Tropical Botany at The Kampong. FIU's CoolTrees initiative specifically examines ground-level cooling beneath urban tree canopies and compares temperatures under trees with areas exposed to full sun.

FAQs

Can trees really cool cities by 10 degrees?
FIU researchers say urban trees can cool areas by as much as 10 degrees.

Are all trees equally effective at cooling?
No. Large, dense canopies generally provide more cooling than palms and some ornamental trees.