When are trees worth millions of dollars? When they cover parts of your city.
Take Tampa, for example, which has established an Urban Forest Management Plan. According to a 2016 assessment by the University of Florida Institute of Food and Agricultural Sciences and the University of South Florida, the city’s 32.3 percent canopy coverage saves Tampa $7 million in annual energy savings, $121 million a year in carbon sequestration and storage, and $3.4 million in storm water treatment savings.
Because trees provide shade and air to breathe, many cities have passed laws to prevent the removal of healthy and structurally sound trees, said Andrew Koeser, a UF/IFAS assistant professor of environmental horticulture based at the Gulf Coast Research and Education Center in Balm.
Koeser and his colleagues wanted to know the impact of tree ordinances on Florida cities’ canopy. He led a newly completed study that looked at 43 cities in Florida. Researchers showed that Florida cities with tree ordinances that protect large trees have 6.7 percent more tree canopy coverage than those that don’t.
Some densely populated cities are only covered with, say, 17 to 18 percent tree canopy coverage, so 6.7 percent represents a significant increase, Koeser said. For example, in a city the size of Tampa this canopy increase could translate into millions of dollars saved each year in electrical and storm water treatment costs.
Although not part of the study, Koeser and his team have offered an example, given their past work quantifying tree-related benefits in Tampa. If canopy coverage for this city was increased by 6.7 percent, from 32.3 percent to 39 percent, Tampa could save an additional $1.47 million a year in energy costs.
The latest research shows the effectiveness of tree protection efforts and will inform local governments that are considering tree ordinances, said Koeser, who presented his team’s findings March 21 at the UF/IFAS Urban Landscape Summit in Gainesville.
“Debate about tree ordinances stirred two questions: Do they actually work to help a city maintain the tree coverage that we know saves energy costs and preserves its environmental functions? And if so, what is their impact?” he said.
Some people love trees in urban areas, others are indifferent, while some view the trees as a hindrance to development, Koeser said. “These findings let the public and decision makers weigh these values against data.”
For the new study, Koeser and his team conducted a dot-based canopy analysis of 43 Florida cities, using aerial images from 2014 and pairing the results with a comprehensive survey of urban forestry practices conducted by the University of Wisconsin the same year. Those cities included Sarasota, Davie, Orlando and Fort Lauderdale.
For the analysis, they laid 1,000 random dots over aerial imagery for each city and recorded how many of those dots fell on trees. If, for example, 330 dots fell on trees and the rest fall elsewhere, they estimated 33 percent canopy coverage.
The study has been accepted for publication in the journal Landscape & Urban Planning.
Brad Buck can be reached at firstname.lastname@example.org