2023 State of the Urban Forest Report

Boulder’s urban forest is at a tipping point.

A tipping point

Boulder’s urban tree canopy is at a tipping point. An urban tree canopy is the layer of leaves and branches of trees that provide shade and cover for the ground below. Ours has decreased between 2013 and 2020. Losses due to Emerald Ash Borer (EAB) and other pests, severe weather events, and other causes have outpaced new planting and growth. More of the canopy is at risk, with up to 25% threatened by EAB alone, in addition to threats from other pest species like the drippy blight currently attacking mature red oaks. The map below shows the urban tree canopy in 2013 compared to 2020, clearly showing these losses.

The University Hill Subcommunity illustrates the canopy losses experienced throughout the city from 2013 to 2020. Red shows areas of canopy loss since 2013.

What is the Boulder Forestry team's path forward? The 2018 Boulder Urban Forest Strategic Plan (UFSP)! The UFSP is our roadmap to create a more resilient, sustainable urban forest by maintaining or exceeding a 16% canopy cover throughout the city. It includes short and long-term goals to increase community safety, stabilize the urban tree canopy from losses, and improve the canopy’s overall health. Increased tree planting, ongoing tree maintenance, and collaborating with local, regional, state, and national partners are ways we implement the plan.

This first biennial State of the Urban Forest Report describes the progress made since the approval of the UFSP and outlines priorities to ensure we continue working to achieve our vision of a resilient and sustainable urban forest.

Boulder Parks and Recreation Department's Forestry team works hard to ensure the 50,000 public trees we manage thrive despite the threats of extreme temperature swings, snowstorms, drought, floods, climate change, invasive pests, and the loss of trees due to construction.

Why do we need trees?

We have a symbiotic relationship with trees…we need them and they need us. Together we can ensure Boulder continues to have a healthy, thriving urban forest, for us all, well into the future.

The 2022 Boulder Parks and Recreation Plan has helped us understand how our assets and services, including the urban tree canopy, are distributed throughout the city. This work identified gaps and areas where more investment is needed that can make the most impact for underserved members of the community.

We are committed to improving the equitable distribution of our services.

Our team of seven employees are responsible for all aspects of public tree care including:

tree planting
pruning and removals
an Integrated Pest Management program
tree risk assessments
tree-related emergency response
development review and tree protection during city and private projects
arborist licensing
public education
manage diseased and dangerous trees
supporting Cool Boulder and the PLAY Boulder Foundation’s Tree Trust

Plant a tree in a community and you have created an amenity. Teach a community to maintain a tree and you have created an asset. - Unknown

Tree losses have exceeded tree planting every year since 2014, the first full year after the Emerald Ash Borer was discovered in Boulder.

In addition, the work of Boulder Forestry continues to grow, with both the number of trees pruned and service requests from the community increasing every year since 2019. The number of trees pruned and service requests dramatically increased in 2020 due to a snow storm in September.

Progress on the Strategic Plan

The UFSP is our roadmap for achieving a healthy and sustainable urban canopy. Since 2018, we have made progress on accomplishing the priorities and actions outlined.

Progress was slowed significantly in 2020 due to the pandemic, which resulted in reduced funding and staffing for Boulder Forestry. Despite that slowdown, we have achieved significant gains across the four sections of the UFSP: Plan, Manage, Protect, and Engage

PLAN

Develop and implement a 20-year planting plan

Planting trees today ensures a healthy urban canopy well into the future. Since 2018, we have been developing a tool to prioritize areas for planting. We include information about on-site conditions, urban canopy gaps, and the needs of underserved or underrepresented portions of the community.

We collaborate with multiple city departments to gather the most up-to-date canopy data via light detection and ranging (LiDAR) technology.

Continued planting is crucial to ensure the city meets the 16% urban canopy goal. This will require 1) more focus on areas of low canopy and 2) partnering with city departments to ensure the long-term survival of new trees.

Responding to emergencies

We support the city’s response to storm events, such as the September 2020 snowstorm and the 2021 Marshall Fire. Each event requires a different response and evaluation to help with broken, hanging branches and downed trees.

MANAGE

Improve the overall health of our urban tree canopy

We actively manage the urban tree canopy. To ensure efficient and effective operations we use an asset management system to track tree plantings and maintenance work for us.

The pandemic had a significant impact on our ability to maintain the public tree canopy with staff and budget reductions, followed by challenges in rehiring positions. There continues to be a backlog of deferred maintenance due to these reductions. We are also continuing to work on managing EAB’s impacts on ash trees in the city.

Expand the Public Tree Planting program

In both 2018 and 2019, approximately 500 public trees were planted. Tree planting decreased to approximately 300 public trees planted each year from 2020 to 2022 due to staffing and budget reductions from the pandemic.

We have been able to fulfill more public street tree planting requests each year. Requests for new street trees often come from owner-occupied properties where they can commit to watering the new tree so it will thrive.

Fewer requests for new street trees come from lower income neighborhoods or areas with more rental properties, which tend to have a decreased urban canopy. New approaches in these areas need to be developed to ensure equitable distribution of our urban tree canopy.

Establish a dedicated funding source for Boulder Forestry

City tax dollars fund much of the operations and maintenance completed by Boulder Forestry. Since 2018, we have explored and implemented several non-traditional funding opportunities.

We now have a process to collect tree mitigation fees when public trees are removed or damaged from car accidents, vandalism and development projects.

We partnered with the Arbor Day Foundation and other corporate sponsors to provide free trees to the community from 2017 through 2019.

Continue our Emerald Ash Borer (EAB) response

Since it was first detected in Boulder in 2013, we have successfully slowed the progression of this invasive pest to the surrounding community. We have removed 3,315 EAB-infested trees, treated 1,339 ash trees, and released biocontrols. Over that time, over 4,000 new trees have been planted to begin to replace the canopy lost to EAB.

To combat the threat of EAB, in 2014-2017 we released three different species of stingless, parasitic wasps as a biocontrol to target and kill EAB larvae. We worked with the Colorado Department of Agriculture and the Animal and Plant Health Inspection Service, an agency of the United States Department of Agriculture.

Recent studies show that these wasps kill about 28% of the EAB larvae.

Staff hanging a bolt of ash wood with biocontrol wasps.

The wasps will not eradicate EAB or protect individual ash trees but are part of an integrated pest management plan to help slow EAB’s spread.

PROTECT

Strengthen protections for trees on public property

Public trees can be impacted by development and improvement projects in the city. We have been involved with guiding documents, which protect trees during city projects. These guiding documents include “Green Infrastructure – A Plan for Transportation Landscapes” and the Boulder Parks and Recreation Design Standards Manual .

The city’s Design and Construction Standards were updated in 2022 to include improvements in the tree diversity standards for plantings on public property, changes to the approved tree list, and better requirements for tree planting conditions.

Additional updates are needed regarding the irrigation of newly planted trees in order to balance the trees’ needs with water conservation.

ENGAGE

Partner with community organizations

We are proud to support the work of the PLAY Boulder Foundation Tree Trust, including the hiring of the first Tree Trust Program Manager. The Tree Trust is committed to the health of the urban tree canopy on private property. We also partner with the Cool Boulder Campaign, which recognizes that a healthy urban tree canopy is one of our most impactful natural climate solutions in an urban environment.

The Tree Trust is a program led by the PLAY Boulder Foundation. It’s dedicated to:

educating the community about the importance of trees
growing the tree canopy
improving tree health on private lands.

Develop and expand opportunities for community involvement

Tree Tenders are a part of the community outreach provided through the PLAY Boulder Foundation Tree Trust. We provided expertise and knowledge in seminars and training classes for the first two cohorts of Tree Tenders. In addition, between 2018 and 2019, the Tree Trust provided 1,400 seedlings at no cost and 350 trees were provided at low cost to community members to plant on their private property.

The pandemic halted these efforts but work in 2023 is focused on rebuilding and reinvigorating these community efforts.

As a Tree Tender, I am able to put my love of trees and community into action. I felt really grounded and connected, knowing that I was taking small, but meaningful actions to uplift our community and the planet. - Josh Morin, tree tender and founder of We Love Trees, Inc.

Priorities

We have made progress since 2018, however we still have much to accomplish to achieve our goal of a healthy and sustainable urban canopy that can help mitigate against a changing climate. With our current level of resources and funding, we will continue to prioritize the actions that will have the most positive impact on the urban canopy.

Below are our top priorities for 2023 and 2024 to accomplish our goals across the four UFSP areas of action: Plan, Manage, Protect, and Engage:

PLAN

Diverse tree planting

Our Department Plan identified many commercial areas and underserved communities that are below the citywide goal of 16% tree canopy. A cross-departmental effort will address the impacts of a warming climate, set urban canopy goals by subcommunity and land use, and identify potential planting areas. We will prioritize planting in areas based on heat vulnerability, increased storm water runoff, and equity factors.

He who plants a tree, plants a hope. - Lucy Larcom from "Plant a Tree"

Manage our water use through the city’s drought plan

The city’s drought plan was updated in 2022 and guides us when responding to drought conditions. We will align our outdoor water use with the new drought stages and be good stewards of our water resources while preserving our urban tree canopy.

MANAGE

Expand the public tree planting program

Tree removals are outpacing trees planted due to severe weather events and pest issues. We plan to plant 500 trees every year in city parks and the street right-of-way. We are also developing new processes to track how newly planted trees are doing.

Update the public tree inventory

A tree inventory provides a snapshot of data for an urban forest and loses value over time if not routinely updated. We plan to update the tree inventory every 6-8 years, so we know the current condition, value and maintenance needs for our urban canopy.

Manage the Emerald Ash Borer (EAB)

We have successfully slowed the EAB’s progression within Boulder and surrounding communities, but continued management is needed. We plan to:

increase tree planting
maintain or increase pesticide applications
remove symptomatic public ash trees
release biocontrols to kill EAB larvae
enforce the removal of dying ash trees on private property
increase EAB-related community engagement

Expand the commercial tree program

Trees in commercial areas are subject to additional stressors such as poor soils, limited growing room for roots, reflected heat and lack of irrigation. When trees can’t reach their mature size, the environmental, economic, social and health services are reduced. Then, trees’ ability to draw down and store carbon and mitigate urban heat is more limited.

Boulder’s commercial areas have the lowest tree canopy across the city. These trees need specialized care and both the trees and surrounding hardscapes also have specific maintenance needs to maintain public safety and provide safe corridors.

We want to not only restart and increase the funds for the existing commercial tree program, but also expand the program outside downtown.

Continue and increase routine Forestry operations

To achieve our canopy goals, tree planting must be coupled with protection and maintenance of existing trees on both public and private property. We are seeking additional staff resources to perform routine maintenance, complete deferred maintenance, continue our community programs, slow the decline of our tree canopy, and manage increased industry costs.

PROTECT

Protect trees using city policies, the municipal code, and design and construction standards

We’re responsible for over 50,000 public trees throughout parks and street rights-of-way, however there are over 600,000 trees on other city property and private property not managed by us. We need to protect those trees for heat island mitigation, carbon sequestration, and public health benefits. Investments in additional staff will ensure the appropriate municipal code, policies, development processes, and construction standards are considered by the city to protect these trees, too.

To exist as a nation, to prosper as a state, and to live as a people, we must have trees. - Theodore Roosevelt

ENGAGE

Support the PLAY Boulder Foundation Tree Trust:

The Tree Trust is rebuilding its programs focused on community engagement and the expansion and protection of the urban tree canopy on private property. We will support the Tree Trust so they can continue to engage community members and private landowners who can manage the trees on their properties.

Participate in the Cool Boulder campaign

We already partner with the city’s Climate Initiatives Department on the Cool Boulder campaign and will continue to build this relationship. This partnership addresses climate change through local action, including work on private properties to foster our urban canopy.

Forests are the lungs of our land, purifying the air and giving fresh strength to our people. - Franklin D. Roosevelt

How can you help?

care for trees on your private property by watering, providing mulch, pruning limbs and treating them for life-threatening pests. Get more tips.
plant a tree in your yard
request a free tree be planted in the right-of-way adjacent to your home
support the PLAY Boulder Foundation Tree Trust
become a partner in the Cool Boulder Campaign
become a Tree Tender

Investing in our future

We hope Boulder's first State of the Urban Forest Report helped you understand the importance of our urban canopy and all that the city does to care for it. While momentum to foster the urban canopy slowed during the pandemic, citywide there are efforts underway to achieve the goals of the Urban Forest Strategic Plan.

With Boulder’s urban tree canopy at a tipping point, investment is needed now to achieve our goal of 16% canopy cover throughout the city. Returning to 2013 canopy levels will require enormous action, both public and private. This critical work can only be successful with the support of our community and unprecedented levels of collaboration between public land managers and private landowners.

Trees touch everything. We need them, they need us, and it’s a long-term relationship. The impact of a newly planted tree may not be fully realized for decades, so investment now is critical. We hope that you are inspired to support Boulder Forestry and be involved in your urban forest.

Thank you!