Philip Hewett – Project Coordinator (Temp) – City Greening and Urban Forest Policy Newcastle City Council, NSW

Clark and Matheny  published a model of urban forests sustainability in 1997 1 – I recall reading the article and thinking how far removed we were in Australia from such holistic tree management thinking – that was 1997 yet now 8 years on things look very different. Global warming is ringing alarm bells and sustainability has crept into the people’s dialogue from building to transport and planning. The NSW and SA Local Government Associations have both adopted urban forest policies, and Adelaide City has commenced an ambitious urban forest program whilst the City of Newcastle is drafting a comprehensive urban forest policy. A number of NSW local government Councils have adopted the term ‘urban forestry’ in lieu of ‘tree preservation’ and ‘tree management’. In March 2005 the Lord Mayor of Sydney hosted an Urban Forest Forum and a number of national conferences have focussed on issues in urban forestry.

Given this significant increase in attention to urban forestry in Australia I have set out here what I consider to be a potentially useful model for Australian authorities to take urban forestry into the application phase. I fear that in the absence of a practical model that helps us to understand and apply urban forestry, that our currently dysfunctional approach to urban tree management could become the defacto urban forestry  – ie what we do now simply gets called ‘urban forestry’ – in my view, this would be a disastrous situation.

Broken down to its basics, Clark’s 1997 urban forest sustainability model becomes readily understandable for lay persons and therefore its ideas are transferable. I propose it as a basic model for Australian Local Government authorities seeking to gain from the potentially enormous benefits of their urban forest.

What follows is a summary of the Clark model which itself was adapted from a World Forest Sustainability model 2 Following that I present a sample of the Seattle Urban Forest Assessment: Sustainability Matrix 3 which used the Clark sustainability model, with minor modifications, to identify directions for Seattle urban forest policy and programs.


The four principles to which any model must adhere:

  1. Sustainability is a broad, general goal
  2. Urban forests primarily provide services rather than goods
  3. Sustainable urban forests require human intervention
  4. Trees growing on private land compose the majority of urban forests

Applying these four principles leads to this definition of sustainable urban forest:

“The naturally occurring and planted trees in cities which are managed to provide the inhabitants with a continuing level of economic, social, environment al and ecological benefits today and into the future”

Applying this definition in urban areas means accepting these three premises:

  1. Communities must acknowledge that trees provide a wide range of net benefits – they are essential to the future health of cities and their inhabitants
  2. Given the goal of maintaining net benefits over time, the regeneration of urban forests requires intervention and management by humans ie urban forests are sustained by people not by nature
  3. Sustainable urban forests exist within defined geographic and political boundaries: those of cities – regardless of land ownership

Given these three premises, Clark & Matheny developed their model of urban forest sustainability which is founded on three components:

  1. Vegetation resource (Table 1) the engine that drives urban forest. The composition, extent, distribution, and health define the limit of benefits provided and cost accrued.
  2. Community framework (Table 2) a sustainable urban forest is one in which all parts…
  3. Resource management (Table 3) Not simply management but a philosophy of management…

Achieving sustainable urban forests is founded on four assumptions:

  1. community cooperation – with a shared vision and ever present focus on maximising benefits and minimising costs
  2. quality care – redirecting the traditional orientation of urban tree management away from municipal trees to the mix of public and private trees
  3. continued funding
  4. personal involvement

The Clark urban forest sustainability model was based on the Santiago Agreement 2 which suggested criteria and indicators for the conservation and sustainability of temperate and boreal forests. It recognised that both quantitative and qualitative indicators were needed because not all criteria could be accurately measured.




Performance indicators

 Key objective

Low Moderate Good Optimal
 Canopy cover No assessment Visual assessment (ie photographic) Sampling tree cover using aerial photos Information on urban forest included in city wide GIS Achieve climate appropriate degree of tree cover, community wide
 Age-distribution of trees in community No assessment Street tree inventory, complete or partial Public- private sampling Included in city wide GIS Provide for uneven age distribution
Species mix No assessment Street tree inventory City wide assessment of species mix Included in city wide GIS Provide for species diversity
 Native vegetation No program of integration Voluntary use on public projects Requirements for use of native species on a project appropriate basis Preservation of regional biodiversity Preserve and manage regional biodiversity.

Maintain the biological integrity of native remnant forests.

Maintain wildlife corridors to and from the city



Performance indicators

Key objective

  Low Moderate Good


Public agency cooperation Conflicting goals among departments No cooperation) Informal working teams Formal working teams with staff coordination All departments operate with common goals and objectives
Involvement of large private institutional landholders Ignorance of issue Education materials and advice available to landholders Clear goals for tree resource by private landholders; incentives for preservation of private trees Landholders develop comprehensive tree management plans and fund them Large private landholders embrace city-wide goals and objectives through specific resource management plans
Green industry cooperation No cooperation between segments of industry. (nursery, contractor, arborists) No adherence to industry standards General cooperation between nursery, contractor, arborists


Specific cooperative arrangements  eg purchase certificates for right tree right place Shared vision & goals including use of professional standards The green industry operates with high professional standards & commits to city-wide goals & objectives
Neighbourhood action No action Isolated and or limited number of active groups City-wide coverage and interaction All neighbourhoods organised and cooperating At the neighbourhood level, citizens understand & participate in urban forest management
Citizen-government-business interaction Conflicting goals amongst constituencies No interaction amongst constituencies Informal and or general cooperation Formal interaction eg tree board with staff coordination All constituencies in the community interact for the benefit of the urban forest
General awareness of trees as a community resource Low – trees as problems and drain on budgets Moderate – trees as important to community High – trees acknowledged  to provide environmental services Very high – trees as vital components of economy and environment The general public understands the value of trees to the community
Regional cooperation Communities operate independently Communities share similar policy vehicles Regional planning Regional planning coordination and or management plans Provide for cooperation and interaction among neighbouring communities and regional groups




Performance indicators

Key objective


Low Moderate Good


 City-wide management plan No plan Existing plan limited in scope and implementation Government-wide plan accepted and implemented Citizen-government – business resources management plan accepted and implemented Develop and implement a management plan for trees and forests on public and private property
City-wide funding Funding by crisis management Funding to optimize existing population Adequate funding to provide for net in creases  in population and care Adequate funding , private and public to sustain maximum potential benefits Develop and maintain adequate funding  to implement a city-wide management plan
City staffing No staff No training Certified arborists on staff Professional tree care staff Employ and train adequate staff to implement city-wide management plan
Assessment tools No ongoing program of assessment Partial inventory Complete inventory Information on urban forest  included in city-wide GIS Develop methods to collect information bout the urban forest on a routine basis
Protection of existing trees No policy or policy not enforced TPO present and enforced Tree preservation plan required for all projects, public, private, commercial Integrated planning program for conservation and development Conserve existing resources, planted and natural, to ensure maximum function
Species and site selection Arbitrary species prohibitions No consideration of undesirable species Identification/prohibition of undesirable species Ongoing of adapted high performance species with good site species match Provide guidelines and specifications for species use, including a mechanism for evaluating the site.
Standards for tree care None Standards for public tree care Standards for stock, pruning etc, for all trees Standards part of community wide vision Adopt and adhere to professional standards for tree care
Citizen safety Crisis management Informal inspections Comprehensive hazard program (failure, tripping) Safety part of cost benefit program Maximise public safety with respect to trees
 Recycling Simple disposal by land filling of green waste Green waste recycling Green and wood waste recycling and reuse Closed system, no outside disposal Create a closed system for tree waste

In 2000, the city of Seattle (pop 540,000) USA undertook an assessment of the Seattle urban forest in response to concerns about the impacts of population growth and higher development densities on Seattle’s trees 3. The Seattle assessment used an adapted form of the Clark & Matheny model of urban forest sustainability and may be a useful model for application by Australian cities.

A sample of two criteria (Table 4) from the Seattle matrix illustrates this point. It uses similar criteria to the Clark & Matheny model, which are presented as a matrix to summarise data collected by survey. The matrix included comparisons with several other US and Canadian cities to ‘explore lessons from them & their possible application to Seattle’




Criteria Objective Current Seattle conditions Challenges & opportunities  Other Cities

Lessons learned

City-wide management plan  Develop objectives & implement a management plan for trees on public and private property No city-wide management plan in place Require strategic vision and resources to develop UF management plan, review process and update Servals cities have management plans that are periodically reviewed and updated Adequate support fro tree maintenance is concern of most tree mangers I most US cities
Urban Forest Policy  Conserve/ restore, enhance resources; develop guidelines and standards; ensure citizen safety and benefit Urban Forest Coalition now in process of developing guidelines and approaches; requires political and budgetary support as well as program to educate voters Integrate tree conservation into land use and growth management planning.

Develop tools to increase tree cover in new development

Enforcement of existing ordinances remains a problem as well as development of enforceable new laws

CA cities major challenges are planting/maintenance responsibilities and ownership.

Policy has both UF practices component (internal standards) and city quality component (external audiences)

Some cities policies re: treestewardship(protection and preservation in development ), emergency & storm management, tree valuation, or root protection –ay or may not have code

Tree policy is integrated with other city-wide goals in Boston 400 & The Metropolis Plan

The Clark urban forest sustainability model and the Seattle urban forest assessment matrix could be very easily adapted for application in Australia.

To reiterate, the model has three important components, all three must be present:

  1. Vegetation resource
  2. Community framework
  3. Resource management

We do not need to invent new models – the hard work has been done. The results of such studies conducted in Australia would expose the urban tree management situation for policy makers, politicians, Councillors and administrators in such a way as to reveal the true state of play with each city’s urban trees. This would create the starting point for urban forest action.

Now is as good a time as ever arboriculturists to throw the urban tree management ‘ball’ back to the players who have such significant influence on the design and management of our cities and suburbs, and because of this, exert enormous influence on the structure, extent and future of urban forests. Arboriculturists (and committed associates) must take the role of advocates and activists, prodding for progress and steering it instead of running alone as now and virtually haemorrhaging as a profession in the process. After all, sustainable living is everyone’s goal and therefore it is everyone’s concern.

The urban forest sustainability model is a valid, proven approach that Australian cities could employ as a practical measure to achieving the social and economic health and well being of all who visit, live in and love this country now and in the future.


  • Clark, JR & Nelda P Matheny, Genni Cross and Victoria Wake. 1997 A Model of Urban Forest Sustainability Journal of Arboriculture 23(1):
  • Journal of Forestry. 1995. Sustaining the World’s Forests – The Santiago Agreement. Criteria and Indicators for the conservation and sustainability of temperate and boreal forests.
  • Cascade Consulting Group University of Washington. 2000. Seattle Urban Forest Assessment: Sustainability Matrix Urban Forest Coalition, City of Seattle. (