Transcript How to estimate future forest cover Center for Watershed Protection in a watershed USDA Forest Service, Northeastern Area, State and Private Forestry.

How to estimate
future forest cover
Center for Watershed Protection
in a watershed
USDA Forest Service, Northeastern Area, State and Private Forestry
“Urban Watershed Forestry”
“Watershed forestry is the use of
forests and the practice of forestry to
protect, restore, and sustain water
quality, water flows, and the health
(WFAP federal
and function of watersheds.”
register)
“Urban is ….well….urban developed and developing areas”
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Watershed Benefits of Forest Cover
 reduce stormwater runoff
 improve air quality
 reduce stream channel
erosion
 provide habitat for
terrestrial and aquatic
wildlife
 improve soil and water
quality
 reduce summer air and
water temperatures
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Link Between Forest Cover and
Stream Health
• Stream health rating of Excellent requires no
more than 6% IC and at least 65% riparian
forest cover (Goetz et al, 2003)
• Stream health rating of Good requires no
more than 10% IC and at least 60% riparian
forest cover (Goetz et al, 2003)
• Watersheds with at least 65% forest cover
usually had a healthy aquatic insect
community (Booth, 2000)
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Urban Watershed Forestry
Goals and Objectives:
Protect



Protect priority forests
Prevent forest loss during
development and
redevelopment
Maintain existing forest canopy
Enhance

Enhance forest fragments
Reforest

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
Center for Watershed Protection
Plant trees during development
and redevelopment
Reforest public land
Reforest private land
USDA Forest Service, Northeastern Area, State and Private Forestry
Urban Watershed Forestry Manual Series
part 1: Methods for Conserving
forest cover in a watershed
part 2: Conserving & Planting
Trees at Development Sites
part 3: Urban Tree Planting
Guide
www.forestsforwatersheds.org
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Planning Methods for Increasing
Forest Cover in a Watershed
Step 1. Conduct a Watershed Leaf-Out Analysis
Step 2. Develop forest cover goals and objectives for the watershed
Step 3. Identify existing forest and reforestation opportunities
Step 4. Conduct a field assessment of existing forest and
reforestation opportunities
Step 5. Prioritize existing forest and reforestation opportunities
Step 6. Develop recommendations for meeting forest cover goals
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
The Leafout Analysis
• GIS-based method to estimate future forest
cover in a watershed
• Local governments /watershed groups can use
method to:
• evaluate the effect of different watershed protection
scenarios on future forest cover
• set numeric forest cover goals
• develop watershed protection recommendations
• Leafout Analysis spreadsheet available at:
www.forestsforwatersheds.org
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
GIS data needs for Leafout Analysis
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•
Watershed boundary
Property boundaries and parcel data
Hydrology and roads
Current forest cover
Zoning
Protected parcels– conservation easements,
conservation or parkland zoning
• Land cover coefficients
• Recent aerial photos may also be helpful
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Leafout Analysis Assumptions
• Full buildout of the watershed will occur based
on allowable zoning (e.g., no rezoning)
• Current forest cover on developed land,
protected lands (and agricultural lands with
future agricultural zoning) will remain the same
with the future buildout
• Future forest cover on buildable land can be
predicted by using forest cover coefficients
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Leafout Analysis Caveats
• Intended for use as a planning exercise, not a
precise predictor of future forest cover.
• Does not account for tree removal or mortality
(other than that related to land development)
• Default values are provided but use local data
where available
• Measures forest cover not urban tree canopy
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Forest cover vs. tree canopy
Forest cover: area of land that is
classified as forest.
Tree canopy: layer of leaves,
branches and stems that cover the
ground when viewed from above.
Graphic source: Goetz et al 2003
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Leafout Analysis Steps
1. Calculate current forest cover in the watershed
2. Identify buildable and unbuildable parcels
3. Calculate the area of each zoning category for
buildable land
4. Multiply buildable land in each zoning category
by the corresponding forest cover coefficients
5. Calculate current forest cover on unbuildable
land
6. Sum future forest cover on buildable and
unbuildable land
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 1: Calculate Current Forest
Cover
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 2: identify buildable and
unbuildable parcels
Parcels intersect with
buildings so they are selected
as “developed” parcels
Center for Watershed Protection
No buildings.
Parcels not
selected
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 2: other parcels to consider
“unbuildable”
• Parcels that are permanently protected
from development by easement or other
conservation measure (e.g.,
conservation zoning)
• Lands currently in agricultural use that
also have future Agricultural zoning
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 2: results
Watershed boundary
Unbuildable land
Buildable land
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 3: calculate the area of
each zoning category for
buildable land
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 3: additional data
requirements
• Calculate current forest cover on:
• Buildable very low density residential (e.g., x
du/acre), open urban, and agricultural lands
• Why?
• Forest cover on VLDR and Open Urban land varies
based on pre-development forest cover
• Assumption that most agricultural lands will keep
existing forest if zoned agricultural in the future
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 4: multiply the buildable land in
each zoning category by the
corresponding forest cover
coefficients
• Forest cover coefficients represent the
fraction of a particular land use that is
covered by forest
• Forest cover coefficients vary by land use and
potential natural vegetation (and by predevelopment forest cover for some land use
types)
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Forest Cover Coefficients
Land Use
Description
Forest Cover
Coefficient
Low density residential
1-4 dwelling units (DU) per
acre
0.034
Medium density
residential
5-10 DU/acre
0.033
High density residential
> 10 DU/acre
0.028
Commercial
Retail, small office,
businesses
0.010
Industrial
Manufacturing and industrial
facilities, including
warehouses, office parks
0.005
Institutional
Schools, churches,
government offices and
facilities
0.022
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Predicting Future Forest Cover
on Very Low Density Residential
and Open Urban Land
Land Use
Description
Equation to Predict Future
Forest Cover (%)
Very low density
residential
< 1 DU/acre
Y = 0.71x + 3.97, where:
Y = post-development forest
cover %
x = pre-development forest
cover %
Open urban land
golf courses, parks,
recreation areas
Y = 0.87x + 1.42, where:
Y = post-development forest
cover %
x = pre-development forest
cover %
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 4: Results
Land Use
Buildable
Acres
Forest Cover
Coefficient
Future
Forest
Cover
(Acres)
Low density residential
320
0.034
10.88
Medium density residential 5,600
0.033
184.80
High density residential
232
0.028
6.50
Commercial
99
0.010
0.99
Industrial
34
0.005
0.17
Institutional
23
0.022
0.51
Open urban
47
0.358
16.83
Very low density
residential
28
0.461
12.92
Total
6,383
N/A
233.60
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 5: calculate current forest
cover on unbuildable land
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Step 6: sum future forest cover on buildable
and unbuildable land
+
Future forest cover on
buildable land (estimated
using land cover coefficients):
600 acres
Current forest cover on
unbuildable land: 639 acres
Leafout Analysis Spreadsheet
Compiles result of the Leafout steps
• Input watershed data
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry
Leafout Analysis Spreadsheet
1. Fill in the requested values in the Input Watershed Data
tab (these are derived from GIS analysis)
2. Go to the See Future Forest Cover Results tab to view
the estimated future forest cover and % loss
3. Set an initial forest cover goal and select from four urban
watershed forestry practices in the Select Management
Practices tab
4. Go to the Re-Evaluate Future Forest Cover tab to see the
effect of the selected practices on future forest cover
5. Revisit the Select Management Practices tab and make
changes if desired
6. Use the Finalize Management Practices tab to summarize
your final forest cover goal, management practices and
timeframe for implementation
Urban Watershed Forestry
Practices
• Options in the Leafout Spreadsheet:
• Conserve forest on individual parcels through
purchase /easement
• Adopt a local forest conservation ordinance for new
development
• Implement reforestation projects on public lands
• Initiate an outreach/incentive program focuses on
tree planting for private landowners
• A complete list of urban watershed forestry
practices in available in the manual series
Center for Watershed Protection
USDA Forest Service, Northeastern Area, State and Private Forestry