Monitoring & Maintaining Your Urban Forest

A single one-time inventory will give you a snapshot of where you are. But, like a single physical exam at age 20, it can’t tell you much about your health at 60.

Urban Forestry Toolkit

Monitor: Your management plan must provide for regular “check-ups.”

Unless you periodically review the condition of your urban forest, you can’t know if your programs are working, your trees are growing and healthy, and no risks have emerged that threaten their future.

trained volunteers can help

Software tools empower volunteer stewards.With the right tools, trained volunteers can provide the field force needed to conduct regular inventories and assessments.

Why Monitor?
  • Are your trees growing? After planting, trees need care, especially irrigation in dry climates. New York City took it a step further and linked street tree survival to the biological, social and stewardship goals they’d set.
  • Keep local communities involved. Volunteer tree stewards can become your most ardent advocates. Casey Trees in DC provides tools, training and opportunities for action.
  • Managing risk. The rapid spread of pests and disease threatens many urban forests. Communities afflicted by the emerald ash borer face up to $10 billion in costs to deal with the epidemic. Monitoring and early detection can save millions.
  • Maintaining healthy forests in a climate of change. Not only will trees age and require maintenance and removal, but the environment will change around them — not just climate, but the built environment as well. New developments as well as old infrastructure can all affect tree growth, health and distribution.
  • Performance. Repeated assessments allow for evaluation of canopy cover change. Experts recommend 5-year cycles to learn whether it’s growing, or to identify factors that might be hampering growth.
What you need to know.

Deciding upfront what you’ll monitor and the information you need will help:

  • avoid the inevitable blizzard of raw data that confounds useful analysis;
  • identify the types of techniques and data collection systems most likely to meet your information needs, whether bottom-up or top-down, through tools such as i-Tree Canopy, Healthy Trees, Healthy Cities, or urban forestry consulting firms;
  • garner the support you’ll need from universities, the US Forest Service, and undergraduate and post-graduate students to plan for and conduct analyses of the data you’ll collect; and
  • organize, schedule and staff long-term monitoring initiatives.

Maintain — Investments in maintenance reduce risks and yield ongoing dividends.

Cost-efficient maintenance: Eight steps to a healthy, sustainable urban forest.
  • Plan for Monitoring and Maintenance. Don’t wait until after you need it. That’s disaster response, not maintenance. Make a plan – the best plans involve effectively engaging municipal resources and community stewards. Account for regular monitoring. Together, monitoring and maintenance provide the essential tools to ensure the longevity and continued effectiveness of green infrastructure practices, and reduce risks in terms of infrastructure damage and safety.
  • Staff Resources for Monitoring and Maintenance. Can you do it with your own staff? Do you need to hire more people? Can you engage community stewards?  Will your staff or contractors need specialized training? Or would it be more cost-effective to hire an experienced contractor? Can you enlist other municipal departments which have the equipment and skill-sets to inspect and maintain green infrastructure? To assure consistent application of best practices, rely on ISA-certified arborists and contractors.  Consider how stewardship groups might help with everyday care, and how this may cultivate community and resilience co-benefits.  Developing capacity through partners may take more time upfront but can yield substantial outcomes.
  • Infrastructure for Monitoring and Maintenance. Related to the above (staff resources), do you have the tools you need to monitor and maintain? If your municipality does not already have a contract, plan, or tool, consider publicly-available free tools like those provided by the Healthy Trees, Healthy Cities initiative. If you are looking to design a monitoring program, revisit the Best Practices: Urban Tree Monitoring section above.
  • Identify Maintenance Prompts. Some common problems require “non-routine” maintenance. Help inspectors or community stewards identify these “maintenance prompts” by training and education materials; examples include excess sediment accumulation, trash and debris, overgrown vegetation, dead or diseased vegetation, signs of erosion, structural damage, or standing water present more than 72 hours after a rain storm.
  • Update Standard Operating Procedures. If municipalities have standard operating procedures for routine landscape and infrastructure maintenance, they should be updated to incorporate green infrastructure maintenance triggers and remedial actions. Additionally, if contractors are used to maintain practices, include specific language in contracts that require training of maintenance crews. Maintenance schedules should be set for each type of practice, and a tracking system should be in place to ensure that maintenance is performed as prescribed.
  • Secure Funding for Maintenance. Monitoring and maintaining green infrastructure requires annual budgeting and reliable funding. Sources for capital projects often can’t be tapped for on-going maintenance. Look instead to local sources and consider leveraging civic stewardship capacity and interest.
  • Procure Equipment. Municipalities should also consider the equipment needed to maintain green infrastructure and determine if additional equipment is needed. Most of the necessary equipment is typical of general landscape maintenance. Heavy equipment is discouraged for routine maintenance, because it can cause soil compaction, which reduces the effectiveness of the practices.
  • Enlist the Help of Volunteers or Community Stewardship Organizations. Some routine maintenance, such as removing trash and weeds from bio-retention areas, can be accomplished by partnering with neighborhood organizations, local tree groups, or garden clubs to leverage their funds/volunteers.  Engaging the community more fully in your program will yield substantial and surprising dividends over time.  Stewardship provides meaningful engagement and purpose and will help not just the urban forest, but may also help individuals and communities themselves heal, recover, or unify.

Who Should Maintain Street Trees: Property Owners or the City?

topped tree by private owner

Not a good idea.Courtesy Friends of the Urban Forest, San Francisco

Many cities require property owners to maintain street trees and adjacent sidewalks at the front of their lots. Sometimes it works. Sometimes it doesn’t. After four years of assigning tree and sidewalk care to owners, San Francisco reversed its policy. Through Ballot Proposition E in 2016 [introduced by the City’s Board of Supervisors] the Department of Public Works took over; the initiative included a mandate to fund the program at $19 million annually — enough to sustain the City’s goal of adding up to 50 percent more street trees.


Related Resources
Urban Forestry Toolkit