**This article first appeared in City Trees, The Journal of The Society of Municipal Arborists
Health Strategies Group (HSG) is engaged in analyzing the allergenic impact of urban American forests. To that end the organization has been attempting to secure all available urban forest inventories from the hundred largest cities in the U.S.
Since they began collecting this information, they are finding that some cities have nothing available and others have a lot of detailed information. Some cities have been able to provide inventories specific only to trees planted on city streets and in public park areas. Others have had inventories of plantings (trees, shrubs, flowers, etc.) done for the past several years or for material planted in 1999. Based on this experience, conducting inventories of city trees, although not unheard of, is a more recent undertaking by U.S. cities. More inventories have been completed by smaller cities rather than larger ones.
The driving force behind the study is the incidence of pollen-based allergies and asthma that has exploded in the US, over the past two decades. Since 1980 the number of persons with pollen allergies has doubled, and the incidence of asthma has almost tripled. Approximately 50 million Americans currently suffer from pollen related allergies, and 80% of individuals with asthma also have pollen-based allergies. Second, it is interesting to note that the likelihood of suffering from pollen related allergies is 20% greater for those of us living in urban areas than for persons living in rural areas. Third, according to an analysis being done by the U.S. Department of Agriculture, there appears to be a preponderance of plantings in urban areas that are pollen-intensive. Fourth, there is a dearth of practical information about the allergenic properties of trees and plants typical to urban areas.
HSG is actively engaged in researching the allergenic properties of a wide range of trees, shrubs, grasses, groundcovers, and flowers. They intend to provide information about which trees and other plants are lower pollen producing or pollen-free to organizations involved in large-scale plantings. Upon completion of the work, their findings will be shared with cities and other organizations participating and interested in the study. For each participating city, the report will include an assessment of the potential impact of city plantings on allergy related health conditions and ideas for alternative future plantings that would have fewer allergenic properties. They anticipate that the report will be available later this year.