Assessing Urban Green
David J. Nowak
USDA Forest Service
Northern Research Station
Syracuse, NY, USA
Objective: vision of green infrastructure
drivers and impediments in the planning,
design, building, or management
Measurement is Critical
Structure
Function
Value
Urban Tree Cover
Ecoregion dominates
U.S. example:
– Cities in forests: 34% average tree cover
– Cities in grasslands: 18% average tree cover
– Cities in deserts: 9% average tree cover
– Total greenspace in cities ~ 60%
Percentage Greenspace by Land Use
100
Percent
80
60
40
20
0
Land Use
Urban Vegetation Benefits
Cooler air temperatures
Social / Physiological benefits / Aesthetics
Air quality improvement
Water flow and quality improvement
Building energy conservation
Greenhouse gas reduction
UV radiation reduction
Wildlife habitat
Noise reduction
Human health
Assessing Urban Forests
Top-down approach
Aerial-based
Bottom-up approach
Ground-based
Top-down Approach
Cover Data
Landsat (30 m)
Hi-resolution (~1 m)
Photo-interpretation
Testing NLCD Tree and
Impervious Cover Maps
100%
0%
National Tree Cover Maps
Tree cover underestimation = 9.7%
Tree Cover Mapping
High resolution (typically sub-meter)
cover data
Photo Interpretation
15
PI Mapping
27% tree cover
Change Analysis
2007
2002
60.0%
Year 1
50.0%
Tree Cover
40.0%
30.0%
20.0%
10.0%
0.0%
Year 2
2.0%
1.0%
0.0%
-1.0%
-2.0%
Tree Cover
-3.0%
Absolute Change
-4.0%
-5.0%
-6.0%
-7.0%
-8.0%
-9.0%
-10.0%
Annualized Change
Ground-based Approach: i-Tree
www.itreetools.org
What is i-Tree?
A suite of tools to assess urban vegetation
and their ecosystem services and values
i-Tree Eco = UFORE
Assessing Urban Tree Populations
i-Tree Eco assesses:
Structure
Function
Energy
Air pollution
Carbon
VOC emissions
Value
Management needs
Pest risk
Tree health
Exotic/invasive spp.
Species Composition – Syracuse
sugar maple
14.2%
other species
32.4%
arborvitae
9.8%
European
buckthorn
6.8%
boxelder
6.3%
Norway maple
6.1%
shagbark
hickory
3.4%
1999
staghorn
sumac
4.9%
Norway spruce
5.1%
eastern
hophornbeam
5.3%
black cherry
5.7%
890,000 trees
Other Values
Air Pollution Removal = 169 tons /yr
($850,000/yr)
Total Carbon Storage = 163,500 tons ($3.4
million)
Total Carbon sequestration = 3,900 tons/yr
($81,000/yr)
i-Tree: 2nd Generation
Time series
Integrates with GIS and Google Maps
Conclusion
Urban green infratructure and their benefits can
be assessed
i-Tree can help
dnowak@fs.fed.us
nrs.fs.fed.us/units/urban