They are iconic to Florida, but palm trees offer little shade to urban heat islands and capture very small amounts of carbon, a greenhouse gas contributing to global warming.
South Florida’s palm trees are postcard promises of sighing sea breezes and sandy beaches, but the icon of the tropics may be an impractical adornment in an era of climate change.
From the regal royal palm to the sometimes shabby cabbage, the perennial symbol of the Sunshine State offers little shade to baking urban heat islands and captures minimal amounts of carbon — a greenhouse gas contributing to global warming.
As city officials look for more ways to cool concrete jungles and balance carbon emissions, the priority for new plantings is often broadleaf hardwood trees, not the idyllic palm.
Live oaks can absorb and store 92 pounds of carbon a year with a mature tree’s canopy spanning more than 100 feet. That’s compared to less than one pound of carbon for a royal palm and its compact crown of 15 to 20 fronds.
“People coming from up north or other parts of the country are expecting to see palm trees, so I don’t see them disappearing entirely from the landscape,” said Charles Marcus, a certified arborist who wrote an urban tree management plan for West Palm Beach. “But it would benefit most communities if they increased the percentage of hardwoods and I think it’s something cities will have to consider.”
Palms aren’t even an option at City of West Palm Beach community tree giveaways, and a 2018 city ordinance puts an emphasis on using more shade trees in new construction, especially parking lots where 75 percent of the required trees must now be shade trees.
“We’re not trying to seek out and replace palm trees with canopy trees, but we are looking at if we have to do a replacement, would a canopy tree fit,” said Penni Redford, resilience and climate change manager for West Palm Beach.
Three years of studies in cities including Baltimore, Richmond, Va., and Washington by the National Oceanic and Atmospheric Administration found that areas covered in concrete with few trees could be 17 degrees warmer than shaded areas.
The same study conducted in West Palm Beach this past August found a heat-index temperature of 122 degrees near downtown, compared to 92 degrees taken during the same time period near the wetlands area of Grassy Waters Preserve.
“These are samples taken in one time period and one day out of the year, but given the conditions, the difference is staggering,” said Michael Rittehouse, sustainability project coordinator for West Palm Beach.