Perspectives in Sustainable Management of Urban Forests in Central Arizona

1. Perspectives in Sustainable Management of Urban Forests in Central Arizona Chris A. Martin, PhD Department of Applied Sciences and Mathematics Arizona State University

2. Topics • Urban forestry management: Tree selection, health and mortality in the greater Phoenix area • Factors affecting present day urban forest diversity and cover characteristics • Sustainable Site Initiative (SII) – Prerequisites and credits specific to the urban forest

3. Urban forestry management: Tree selection and mortality in the greater Phoenix area • Urban tree cover is in a long-term decline and is presently about 12%. • Approximate rates of tree mortality are between 5% and 10% per annum. • 55% of urban trees have severe structural and/or disease issues mostly caused by improper design and management. • The ‘quality’ of urban tree selection has declined with the increased focus water conservation and xeric and desert landscaping design motifs.

4. Native desert adapted trees have a sprawling, shrub like form unsuitable for spatially congested urban spaces

5. An unsustainable trajectory

6. An unsustainable trajectory

7. June 2005 Crown thinned 3 2 1

8. January 2007 3 1 2

9. October 2008 Crown raised

10. September 2010

11. The capacity to recover from crown thinning deceases with tree age. 100% 75% Productive 50% Fraction of tree crown thinned Mature 25% Establishment 0% Relative Tree Age

12. Factors affecting present day forest diversity and health in the greater Phoenix area • Overall, tree diversity and health in residential areas is higher than in public areas. • Bottom-up driving forces are the principal means of increasing urban forest tree diversity. • Urban tree diversity is strongly correlated to medium family income. • Tree cover in lower income areas of the greater Phoenix metropolitan is in very decline.

13. 1920 Phoenix Chamber of Commerce Report “Phoenix is a modern town of forty thousand people, and the best kind of people too. A very small percentage of Mexicans, Negroes, or foreigners.” (courtesy of Bob Bolin) Social History – Origins of Residential Segregation

14. Social and Technological Legacies A change from function to form

16. Top 5 neighborhood tree species Leucaena glauca 39% Prosopis hybrid 12% Melia azederach 6% Washingtonia filifera 4% 61% The inequities in tree cover within lower income neighborhoods Tree height (m) Park 4.0+1.7 Neighborhood 3.9+1.9 Tree canopy width (m) Park 4.9+2.3 Neighborhood 3.8+2.2 Percent total tree cover Park 3.7% Neighborhood front yards 23.3% South Phoenix neighborhood

17. Naturalizing trees – an urban forest resource? Leucaena glauca (lead tree) South Phoenix neighborhood

18. What is the Sustainable Sites Initiative (SSI)? An interdisciplinary effort to create voluntary national guidelines and performance benchmarks for sustainable landscape design, construction and maintenance practices. • Site Selection • Pre-Design Assessment and Planning • Site Design—Water • Site Design—Soil and Vegetation • Site Design—Materials Selection • Site Design—Human Health and Well-Being • Construction • Operations and Maintenance • Monitoring and Innovation

19. Why is it important that my company know about the SSI guidelines now? Early transformation of company operations to adopt relevant sustainable landscaping practices will place the company in a competitively favorable position. Sustainable Facts In the continental U.S., carbon sequestration provided by urban trees is estimated to be about 25 million tons per year, which is equivalent to the carbon emitted by almost 18 million cars in one year.   ~ Nowak and Crane, 2002; U.S. Climate Technology Cooperation, 2007

20. What are Ecosystem Services? The SSI guidelines are based on the concept of ecosystem services. Ecosystem services are one way that people can use to derivelandscape value. Ecosystem services are the capacity of natural process to provide goods and deliver values that satisfyhuman needs either directly of indirectly. Sustainable Fact Weather-based irrigation systems can reduce irrigation water use by 20 percent in the United States, which is 24 billion gallons per year.   ~ U.S. EPA, 2007

21. What are Ecosystem Services? • Deliverables are broadly placed into four major groups: • Regulation functions – Greenhouse gases (CO2) and microclimate regulation, soil disturbance and retention, and water conservation, soil retention, nutrient cycling, waste treatment, pollination. • Habitat functions - Refugium and nursery functions for the dwelling and reproduction of other organisms such as birds, hummingbirds, butterflies, etc. Sustainable Fact Weather-based irrigation systems can reduce irrigation water use by 20 percent in the United States, which is 24 billion gallons per year.   ~ U.S. EPA, 2007

22. What are Ecosystem Services? • Deliverables broadly placed into four major groups: • Production functions - Food, raw material, and genetic, medicinal, and ornamental resources. • Information functions - Beauty, recreation and tourism, cultural and altruistic inspiration, spiritual and historic inference, and science and education. Sustainable Fact Sediment runoff rates from construction sites can be up to 20 times greater than agricultural sediment loss rates and 1,000 to 2,000 greater than those of forested lands.   ~ U.S. EPA, 2005

24. How are the SSI guidelines organized? The SSI guidelines will be organized into suites of landscape pre-requisitesand credit options. Landscape pre-requisiteswill first need to be adopted as a precursor for the implementation of any desired suite of credit options. Sustainable Fact An estimated 32 million tons of construction and demolition wood waste are generated each year in the United States, 14 million tons of which are potentially available for recovery.   ~ McKeever, 1996

25. How are the SSI guidelines organized? Credit options will be assigned point values associated with low, moderate or high levels of compliance for each and any credit option. 2009 Rating System: 250 Points Total 100 points (40% of total points) 125 points (50% of total points) 150 points (60% of total points) 200 points (80% of total points) Sustainable Fact Maintenance over a 20-year span for a non-native turf grass landscape can cost almost seven times more than the cumulative costs of maintenance for a native prairie or wetland.   ~ U.S. EPA, 2007

26. How are the SSI guidelines organized? Sustainability accreditation and levels of sustainability certification will be derived through demonstrations of a project’s adoption of a suite of pre-requisite and credit options that collectively sum to some standardize cumulative point total. Sustainable Fact Thirty-six states anticipate local, regional or state-wide water shortages in the next five years. ~ U.S. EPA, 2007

27. Credit 3.5 - Minimize or eliminate potable water consumption for irrigation Intent Limit or eliminate the use of potable water, or other natural surface or subsurface water resources available on or near the project site, for landscape irrigation. Non potable water is defined as captured rainwater, recycled wastewater, recycled gray water, air-conditioner condensate, or water treated and conveyed by a public agency specifically for non-potable uses. • Note: Water volume used to irrigate community vegetable gardens is exempt from total site irrigation calculations. Credit 3.9 - Use native plants Intent Plant appropriate vegetation that is native to the ecoregion of the site. Note: Native plants are defined as: plants native to the EPA Level III ecoregion of the site OR known to naturally occur within 200 miles of the site.

28. 4.11 Credit - Use vegetation to minimize building cooling requirements Intent Place vegetation and/or vegetated structures in strategic locations around buildings to reduce energy consumption and costs associated with indoor climate control. 5.2 Credit - Support sustainable practices in plant production Intent Purchase seeds and plants from providers that reduce resource consumption, waste, and risks of invasive species. 7.3 Credit - Recycle organic matter generated during site operations and maintenance Intent Use vegetation trimmings generated during operations and maintenance as compost and mulch to improve soil health and reduce the need for chemical fertilizers, irrigation, and pesticides.

29. Sustainable urban tree selection

30. Conclusion Five keys to developing a sustainable urban forest Key #1: Irrigation technologies Key #2: Oasis Landscape Design Motifs Key #3: Cluster planting of trees Key #4: Green waste recycling Key #5: Pruning practices

31. Where did all the trees go?

32. Acknowledgements Research Collaborators Dr. Bob Bolin, Arizona State University Dr. Anthony Brazel, Arizona State University Dr. Sharon Harlan, Arizona State University Dr. Jean Stutz, Arizona State University Dr. Darrel Jennerette, University California Riverside Dr. William Stefanov, NASA Grant Funding International Society Arboriculture National Science Foundation UVCC Project CAP LTER Project