Grantee Research Project Results
2007 Progress Report: Creating Sustainability Indicators to Assess the Physical, Social, and Economic Values of Greening Cities - A Study of the Million Trees Initiatives in Los Angeles, CA
EPA Grant Number: R833364Title: Creating Sustainability Indicators to Assess the Physical, Social, and Economic Values of Greening Cities - A Study of the Million Trees Initiatives in Los Angeles, CA
Investigators: Saphores, Jean-Daniel , Gillespie, Thomas W , Pataki, Diane , Saatchi, Sassan , Pincetl, Stephanie
Current Investigators: Saphores, Jean-Daniel , Gillespie, Thomas W , Pataki, Diane , Pincetl, Stephanie
Institution: University of California - Irvine , University of California - Los Angeles
EPA Project Officer: Hahn, Intaek
Project Period: March 1, 2007 through February 28, 2010 (Extended to February 28, 2012)
Project Period Covered by this Report: May 1, 2007 through February 28,2010
Project Amount: $299,985
RFA: Collaborative Science And Technology Network For Sustainability (2006) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , Sustainable and Healthy Communities
Objective:
The goal of this project is to understand various impacts of urban forests (physical, social, economic), to build sustainability indicators for the man-made and the natural infrastructure, and to shed light on the social dynamics of implementing sustainability in large urban areas.
Progress Summary:
During our first year, we gathered data on the sale of single and multi-family buildings in Los Angeles in 2004, as well as neighborhood variables and the urban forest in the city of Los Angeles. We also started our hedonic pricing modeling for multi-family buildings; we also conducted a series of <em>in situ</em> measurements of water use of various urban trees and various related environmental effects. In addition, we started mapping the heat island effects and we started to analyze links between surface temperatures and tree canopy cover. Finally, we met with a number of stakeholders and started crafting sustainability indicators for the man-made and the natural infrastructure in Los Angeles.
I) Work status/ work progress
The main tasks undertaken during the review period are detailed below.
A. Quantifying the Value of Urban Forests (Jean-Daniel Saphores and Wei Li)
During this first year, we finished collecting data for our hedonic models, we completed an extensive literature review of the hedonic literature dealing with the housing market, and we started modeling prices of multi-family buildings.
We checked for spatial autocorrelation using ArcGIS (Moran’s I test) and found that house prices are significantly clustered within the City of Los Angeles. This led us to consider the two basic modeling approaches for accounting for spatial effects in our hedonic models: spatial-lag and spatial-error models.
A spatial-lag model assumes that the price of each building is indirectly affected by the spatially weighted average of housing prices in its neighborhood (Kim et al., 2003). To define a neighborhood of a given building, we considered both distances (varying between 2 and 4 kilometers) and zip codes to define neighborhoods. They gave similar results.
The Spatial-Error Model models instead spatial dependence via the error term. It assumes that the price at a location is a function of local characteristics and of omitted variables at neighboring locations. Both spatial-lag and spatial-error models can be estimated by maximum likelihood.
To capture tree canopy cover, we considered a concentric circle centered on each multi-family building in our sample, and calculated (using GIS) the % covered by trees, the % covered by irrigated grass, and the % covered by non-irrigated grass. We created similar variables for each parcel.
B. Water use and environmental effects of urban forests (Diane Pataki and Heather McCarthy)
Four sites in Los Angeles and Orange County have been instrumented with sap flow and meteorological sensors to study the factors that control whole tree water use of common species in the Los Angeles urban forest. These sites include:
- Street trees in the Wilshire area of Los Angeles composed of a mixture of seven California sycamore and London plane trees.
- The LA Zoo and Botanical Gardens, with measurements on 7-8 individuals of Canary Island pine, jacaranda, floss silk tree and sumac.
- The University of California, Irvine campus, with measurements on five individuals each of California sycamore and Canary Island pine.
- Starr Ranch Audubon Reserve, a control site with native vegetation, no irrigation or fertilization, with measurements on eight California sycamores and eight coast live oaks.
The selected species are commonly planted in the study region, and also allow for comparisons of the water use of the same species under different environmental conditions, i.e. urban vs. non-urban and coastal vs. inland climates. The experimental design also allows comparisons of the water use of species with differing characteristics such as: a) diffuse-porous vs. ring-porous; b) deciduous vs. evergreen; and c) native vs. non-native. At each site, we are monitoring whole tree water use, air temperature, humidity, radiation, and soil moisture. We are also making detailed measurements of plant physiology including leaf level gas exchange, vulnerability to cavitation, and leaf nutrient and isotopic composition.
C. Designing sustainability indicators for the urban forest (S. Pincetl, J-D Saphores, T. Gillespie)
To start crafting meaningful sustainability indicators, we organized on January22, 2008, a workshop at the institute of the environment at UCLA with Public Works Commissioner Paula Daniels, representatives from various NGOs (Northeast Trees, Livable Places, and Global Green), MTA, the City of Santa Monica, some academics, and a couple of students. We also met with Suzanne Scheideker-Cook to coordinate interviews with sustainability liaisons from the Bureau of Public Works.
D. Social learning and development indicators (Stephanie Pincetl)
During the report period, we made progress in understanding the complex organizational structure of the implementation of the Los Angeles Million Tree program. We have begun to develop models to describe the new and interdependent form of “governance” responsible for planting a million trees, and the process of institutional learning over the implementation of the program.
We attended sustainability meetings in Public Works, interviewed key personnel for the Million Trees Initiative based in the Mayor’s office, and talked with representatives from different NGOs involved in tree planting in Los Angeles.
E. Mapping heat-island effect (Sassan Saatchi)
During the review period, we collected data of surface temperature for different days during the year as well as corresponding land use data. We then randomly selected 300 sites where we had clear information about land use. We are in the process of modeling the relationship between land cover and surface temperature. Preliminary results suggest that increasing tree canopy cover significantly decreases surface temperature.
Results
A. Quantifying the Value of Urban Forests (Jean-Daniel Saphores and Wei Li)
After carefully going through our data, we built a dataset with 728 transactions of multi-family buildings in the City of Los Angeles in 2004 (see Figure 1 below).
Figure 1: Multifamily house sales in 2004 and ground cover.
For our hedonic models, coefficients of most structural characteristics are statistically significant and have expected signs; results appear robust across models. Multifamily house prices increase with structural square footage, with the number of units, with the number of bedrooms, and with the availability of heating; they decrease with age. Lot square footage is insignificant; one explanation is that most multifamily houses in LA are rentals and renters are likely to be low income families who care less about yard size than buyers of single detached homes.
Results for neighborhood characteristics are also robust across models. Unfortunately, results for tree canopy cover do not appear to be robust yet. The impact of the size of the tree canopy cover on the value of a multi-family building seems to vary with income and with the crime rate. Preliminary results suggest that the value of the tree canopy cover increases with income in the immediate vicinity of a multifamily building.
During the next reporting period, we will be checking the robustness of our results. In addition, we started cleaning-up our dataset for single family buildings.
B. Water use and environmental effects of urban forests (Diane Pataki and Heather McCarthy)
Findings are thus far preliminary. Of interest so far, urban sycamores in Los Angeles showed strong stomatal control over water loss in response to vapor pressure deficit (VPD), a measure of atmospheric dryness (Figure 2). This is in contrast to our hypothesis that sycamores would show little stomatal control based on previous work on riparian tree species. There is also an initial indication that the native California species has higher rates of water use per unit sapwood area than the imported, horticultural hybrid London plane tree (Figure 2).
Figure 2. Daily average sapflux density (g m-2 s-1) in response to vapor pressure deficit (VPD) for street trees (London plane and California sycamore) in the Wilshire area of Los Angeles.
We also measured stomatal conductance of California sycamore and Coast Live Oak trees growing in irrigated and non-irrigated microsites in Irvine, CA. Plants regulate the aperture of stomata, small pores on the leaf surface, to control their water use. Stomatal conductance per unit leaf of Coast Live Oak was higher than sycamore. This was also contrary to our expectations based on previous data. The diurnal pattern of stomatal conductance was more closely related to irrigation than to species, with non-irrigated trees showing midday stomatal closure in both species. We are further investigating species differences in water use and water relations in order to inform stakeholders about the most suitable trees for planting in water limited Los Angeles. We are also investigating the mechanisms underlying differences in physiology of irrigated vs. non-irrigated trees, which likely involve differences in plant anatomy resulting from developmental differences under varying watering regimes.
D. Social learning and development indicators (Stephanie Pincetl)
We are using a self-organizing, heterarchic governance framework to understand how the MTI program works. Governance describes a changed relationship between state and society such that programs and policies are executed through collaborations and cooperation with non governmental actors. A heterarchy is a system of organization that has a multiplicity of actors with divergent internal systems of organization (a city bureaucracy and a non-profit in our case), but who are interdependent and have overlapping goals.
Future Activities:
Continue tasks undertaken plus start analyzing the changes in the landscape and of the spatial patterns of vegetation in Los Angeles using historical records.
III) Planned activities for the subsequent reporting period
We are planning on continuing the tasks already started; in addition, we will start an analysis of the changes in the landscape and of the spatial patterns of vegetation in Los Angeles using historical records.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 23 publications | 16 publications in selected types | All 16 journal articles |
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Type | Citation | ||
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Bijoor NS, McCarthy HR, Zhang D, Pataki DE. Water sources of urban trees in the Los Angeles metropolitan area. Urban Ecosystems 2012;15(1):195-214. |
R833364 (2007) R833364 (Final) |
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Saphores J-D, Li W. Estimating the value of urban green areas: a hedonic pricing analysis of the single family housing market in Los Angeles, CA. Landscape and Urban Planning 2012;104(3-4):373–387. |
R833364 (2007) R833364 (Final) |
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Supplemental Keywords:
Sustainability indicators, sustainable development, environmental policy, environmental decision making, environmental planning, green infrastructure, systems modeling, monitoring, measurement methods, environmental education, ecological and economic modeling, GIS, conservation, ecosystem management, water supply;, RFA, Scientific Discipline, Sustainable Industry/Business, Sustainable Environment, Technology for Sustainable Environment, Environmental Monitoring, Ecology and Ecosystems, green design, ecological design, environmental sustainability, alternative infrastructure design, sustainable urban environment, economic input output, environmental education, million trees initiativeRelevant Websites:
http://www.ioe.ucla.edu/ucpe/people.html ExitProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.