Trees Count! Results
The results of the 2005-2006 census allow us to characterize the street tree population according to species, size, condition, and a host of other factors. In all, surveyors counted 592,130 trees--93,660 more than in 1995-1996, a 19% increase.
Species. The most common street tree in New York City is the London planetree. This venerable urban tree, platanus x acerifolia, has been a mainstay of the urban environment for almost a century. Although the London planetree just edges out the second most numerous street tree, the Norway maple, its canopy covers more than double the land area than its closest rival.
Importance Value. Importance value is a measure of a species’ dominance within a population. It is an average of overall size, leaf area, and canopy cover. London planetree is twice as significant as Norway maple in our current street tree population. Pin oak, which has fewer trees than callery pear, has a higher importance value due to its larger stature and leaf size. An importance value greater than 25 indicates too much reliance on a species, which can subject a population to sudden catastrophe in the face of insects and disease.
|Top Five Species|
|Total Trees||Canopy Cover||Importance Value|
Condition. Just over 90% of the trees were rated in good to excellent condition.
Size. Census takers measured the girth of each tree at chest height. Onequarter of all street trees citywide are small, with Manhattan having the highest percentage of small trees (35%). Five percent of trees are extra large (over 30 inches wide), with Queens having the highest percentage of extra large trees (6.3%). Most (70%) of the City’s largest street trees are comprised of just three species: London planetree, pin oak, and silver maple. By contrast, there is much greater species diversity in the small tree population (14 species in the first 70%).
Damage. Street trees are located on the busy interface between humans and nature, and as such are vulnerable to environmental and physical damage. Signs of damage include torn bark, wounds or cavities on the trunk and branches. Causes of such damage can include vehicles, vandals, or animals. Over 15% of our street trees have trunk wounds (89,211), with 6.6% having torn bark (39,524) and 5.3% with cavities of some type (31,103).
|# trees||% total|
Conflicts. Overhead wires are the predominant urban infrastructure that conflict with trees in all neighborhoods in New York City with the exception of Manhattan. More than 35% of the City’s street trees are growing under wires. Other urban conflicts common to street trees are listed below.
Preliminary Management Observations. With the data from the census, there are a few key insights that have begun to emerge that will help us as we go forward:
- London planetree is our most important species and should always have some representation in our tree population;
- Almost 31% of our street tree species are susceptible to the Asian Longhorned beetle and our planting practices need to continue to strive for increased diversity, and reduced susceptibility to pests and diseases;
- Large, canopy trees confer the most benefits and we need to continue to focus on planting large tree species that will successfully mature.
Did You Know?
A 31 inch wide sweetgum in Queens is 134 years old. Though not the oldest or the largest street tree in the City, it is the oldest of those that we have measured by counting tree rings.
Then & Now
- In the 1995-1996 census, Norway maple comprised almost 23% of the street tree population and was the most populous species. It has now dropped to 14% of the population. The explanation? Over the past decade this species has made up more than 60% of all dead tree removals due to poor health.
- In the 1995-1996 census, over 2% of the population was dead at the time of the inventory (13,154 trees). This time, despite counting almost one-fifth more trees, only 1.4% (8,113) were found to be dead. What changed? Parks instituted a new dead tree removal service commitment, whereby dead trees are removed within 30 days of request. Parks meets this commitment 95% of the time.