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UF/IFAS study: Good tree care should yield environmental benefits

Urban forestry in Tampa Bay, Florida.

Please see caption below the story.

GAINESVILLE, Fla. — Trees shade our homes and help clean the air of our cities. However, their production in the nursery and maintenance in the landscape requires energy and material resources. Some of those processes are mechanized and release greenhouse gases like carbon dioxide.

Understanding this balance between tree environmental costs and benefits is crucial to those who plan and plant urban forests as it can help inform species selection, site development and prescribed care measures, says a University of Florida Institute of Food and Agricultural Sciences researcher and UF/IFAS Extension specialist.

In addition to providing shade, trees take in carbon dioxide – a greenhouse gas – and convert it and store it as carbon in their woody tissues. Trees generally provide the greatest environmental and economic benefits as they mature and grow to a significant size, said UF/IFAS environmental horticulture assistant professor Andrew Koeser.

In a newly published study, Koeser and Aaron Petri of the University of Illinois used a concept called “carbon neutrality” to examine tree benefits. When trees start storing more carbon than they emit – offsetting the amount spent by nurseries and foresters in tree care, that’s called “carbon neutrality.” That care can include planting, water, pest control, mulching, pruning and more.

“In general, the bigger the tree, the more environmental benefits you receive. Over time, the benefits of a tree finally equal its associated costs, with regard to carbon balance,” Koeser said. “I like to think of this as the tree paying back the environmental debt. If the tree doesn’t get to this point, it is emitting more carbon dioxide than it’s taking in and does a disservice to the environment.”

“To truly break even, you don’t just cancel out the carbon associated with your care and maintenance, you need to cancel out the emission associated with tree removal and disposal,” Koeser said.

For the new study, Koeser surveyed urban foresters in the Chicago metropolitan area to see how they grew, planted and maintained maple trees. Among their many results, Petri, Koeser and their research team found that when foresters changed their tree management practices, such as pruning cycles, they could significantly lower the age at which a tree changes from being a carbon emitter to being a carbon sink.

“Despite the specific location and type of tree, Koeser said the findings apply to urban forest programs anywhere. More than half the global population lives in cities, a number expected to increase to 70 percent by 2050, all the more reason for Petri, Koeser and their colleagues to study urban forestry costs versus environmental benefits.

Trees store more and more carbon as they grow, said Koeser, a faculty member at the UF/IFAS Gulf Coast Research and Education Center in Balm, Florida. The same holds true for shade. It can take decades for a tree to get to the size where it shades a house. That’s why it’s so critical to properly maintain trees that are part of a tree-planting program, he said.

The study is scheduled to be published in December in the Journal of Environmental Horticulture.

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Caption: In a newly published study, Andrew Koeser, a UF/IFAS assistant professor of environmental horticulture, and Aaron Petri of the University of Illinois used a concept called “carbon neutrality” to examine tree benefits. When trees start storing more carbon than they emit – offsetting the amount spent by nurseries and foresters in tree care, that’s called “carbon neutrality.” That care can include planting, water, pest control, mulching, pruning and more.

Credit: Tyler Jones, UF/IFAS photography

By: Brad Buck, 352-294-3303, bradbuck@ufl.edu

Source: Andrew Koeser, 813-633-4150, akoeser@ufl.edu