If you look at trees, especially in Florida’s urban areas, you’ll generally see southern live oaks or cabbage palms, the two most common species in the Sunshine State’s cities.
Most of America’s cities rely on a half-dozen species for the majority of their street and park trees. But there are so many more kinds of trees that you could plant and grow. In North America alone, there are 11,000 tree species, according to Dr. Andrew Koeser, a University of Florida associate professor of environmental horticulture.
dr Koeser told participants at the UF Urban Landscape Summit in April that it’s important to plant lots of different kinds of trees in cities so they survive and to increase wildlife habitat, among other reasons.
If you look at Florida, only 10 species make up 63% of Tampa’s inland urban forest, and a similar pattern can be found in other Florida municipalities. But if you plan different types of trees in urban areas, you can reduce maintenance costs and infrastructure damage.
“A lack of species diversity sets the stage for tree loss in the face of diseases or pests that prey on certain trees,” stated Dr. Koeser a faculty member at the UF/IFAS Gulf Coast Research and Education Center, in a news release.
For example, in Florida, palm trees are often an iconic and abundant feature of the state’s urban areas. Lethal bronzing, which affects a wide range of palms — but is particularly devastating to date palms — is infecting palms throughout the state. Mass plantings of the same species over and over again can be particularly hard hit by lethal bronzing, as it has spread to about 30 of Florida’s 67 counties.
In response to a question about the state’s use of mostly palm trees at interstate highway interchanges, Dr. Koeser responded he has worked with the Florida Department of Transportation on its tree maintenance efforts, but was not involved in the initial establishment of their roadside plantings.
“There is a balance that needs to be struck between design aesthetics and diversity,” he stated in an email. “As we continue our efforts we will continue to reach out to landscape architects to show them the risks associated with the continued use of large blocks of the same species.
“This dependence on a small subset of trees is largely driven by market forces, public policy and a lack of familiarity surrounding underused tree species,” Dr. Koeser stated in the release. “This often results in tree loss and reductions in the air filtering and shading services they provide.”
Other losses include:
•Removing trees. With tree loss can come loss of canopy, which translates to an increase in problems like urban heat island effect as well as stormwater flooding.
•Reduced access to greenspace, which is necessary for human health and wellbeing.
To bring different kinds of tree species to cities, Dr. Koeser and a colleague from Iowa State University are working with a $50,000 US Department of Agriculture grant to learn how urban areas across the country use various tree species.
dr Koeser and Grant Thompson, an assistant professor at Iowa State, along with a set of national collaborators, are conducting focus groups. Also, they’re interviewing tree growers, landscape architects, urban foresters, governmental authorities and representatives of government and nonprofit organizations from across the United States.