TO: COMMUNITY SERVICES COMMISSION
FROM: JEREMY SWAN, COMMUNITY SERVICES DIRECTOR
DATE: MAY 1, 2024
Reviewed by:
City Manager: n/a
SUBJECT:
Title
URBAN FOREST UPDATE - 2023
Body
SUMMARY
The Community Services Department is charged with the maintenance and care of the urban forest, including all planting, trimming, removal, and, when necessary, treatment of all City trees. Currently, the City’s urban forest is comprised of over 25,000 trees of over 300 unique species, with an estimated value of over $96 million. Each year Community Services staff outlines a maintenance plan for the urban forest based on the Tree Policies and Guidelines Manual and best practices of the industry. As staff works through the annual work plan, any changes to the local and regional urban forest are noted, and adjustments to the annual work plan are made as needed. This report serves as an update on the urban forest condition and activities over the past year.
RECOMMENDATION
Recommended Action
Staff recommends the Community and Human Services Commission receive and file this report.
Body
ALTERNATIVES TO RECOMMENDATION
In addition to the recommendation, there is the following alternative:
• Refer the matter back to staff for additional information.
FINANCIAL REVIEW
The staff cost to prepare this report is estimated at $1,000 and is included in the operating budget of the Community Services Department.
ANALYSIS
The Community Services Department is charged with the maintenance and care of the urban forest. Under the direction of the Community Services Director, the Community Services Manager oversees the day-to-day operations of urban forest maintenance. Staffing for urban forest maintenance consists of one full-time Arborist and one full-time Maintenance Craftsworker I. The City Arborist oversees maintenance activities, makes inspections, and plans for the future of the urban forest. Due to the magnitude of the urban forest, the City outsources urban forest maintenance activities, and the City Arborist works closely with the contractor to ensure that the urban forest is maintained to City standards. West Coast Arborists, Inc. (WCA) has been the City’s urban forest maintenance contractor for over 15 years.
CURRENT STATUS OF THE URBAN FOREST
As of April 2024, the urban forest consists of approximately 25,000 trees, with a total value of approximately $96 million. Tree value is based on size, location, and species rating.
Tree Count over Time
About ten years ago, the urban forest was home to approximately 27,000 trees. Tree removals were primarily determined by the budget, and trees were removed as funding allowed. This meant that many dead, diseased, or hazardous trees were left in the ground until removal funding was available. Tree planting was not mandatory, and funding was limited to 200 trees per year. Additionally, during this time frame very little outreach was conducted to encourage reforestation.
In 2014, the Liquidambar mitigation plan was approved to begin removing liquidambars that showed signs of Xylella. This time was also faced with several years of drought and water restrictions, which greatly affected the rate of removal. Mandatory replanting began in 2014, as well. Although trees were planted at the rate they were removed, water restrictions led to property owners not watering the newly-planted trees. This led to a higher failure rate of newly-planted trees.
During 2018-2021, the reforestation program was funded through grant funds, which increased the number of tree plantings and leveled removals versus plantings. In 2019, Invasive Shot Hole Borer was identified in the City, which led to increased removals of affected species. In 2020, during COVID restrictions, there was very limited interest in tree plantings.
The significant decline in tree count in 2022 and 2023 is due to the Windstorm of 2022. However, in 2023, the number of tree plantings increased over the number of trees removed, which helped counter a significant decline in the urban forest. Below is a chart showing the number of trees in the urban forest over the past 10 years.
As the urban forest becomes healthier and potentially-high-risk trees are slowly removed, staff will focus on increasing reforestation outreach with a focus on planting “the right tree in the right place.” Outreach will continue on the proper watering of trees to educate residents on proper watering during the different weather conditions. Healthier trees lead to a healthier, sustainable urban forest.
Tree Diversity
The type of trees in the urban forest greatly affects the benefits produced, maintenance activities, and the urban forest budget. Based on tree inventory data, Claremont’s urban forest contains over 300 unique species, the top ten species being:
Top 10 Species
|
Percentage of Urban Forest |
Species |
|
8.4% |
CRAPE MYRTLE |
|
7.5% |
COAST LIVE OAK |
|
5.8% |
CALIFORNIA SYCAMORE |
|
4.0% |
JACARANDA |
|
3.6% |
HOLLY OAK |
|
3.3% |
CANARY ISLAND PINE |
|
2.8% |
AMERICAN SWEETGUM |
|
2.8% |
CHINESE PISTACHE |
|
2.3% |
OLIVE |
|
2.0% |
MAIDENHAIR |
Size and Age Distribution
An urban forest with a wide age range offers a continuous flow of benefits and allows for better planning of urban forest activities. A tree’s age is determined by its diameter at breast height (DBH), or 4.5’ from the base of the tree. Below is the City’s current DBH distribution compared to the ideal distribution according to the U.S. Forest Service:
|
DBH (inches) |
Total |
Current Percentage |
Ideal Percentage |
|
0-6 |
6,345 |
25.4% |
40% |
|
7-12 |
6,450 |
25.8% |
25% |
|
13-18 |
6,266 |
25.0% |
15% |
|
19-24 |
2,540 |
10.2% |
10% |
|
25-30 |
2,511 |
10.0% |
6% |
|
31+ |
904 |
3.6% |
4% |
|
Total: |
25,016 |
|
|
Because the City’s urban forest age distribution is inconsistent with the ideal, the City should continue replacing trees annually to reach the ideal age distribution.
Geographical Distribution
Utilizing a geographic grid system allows staff to plan and budget for routine tree maintenance activities, including trimming and removals. Additionally, grids show where reforestation efforts should be focused. There are five geographical grids. Below is an overview of the number of City trees in each grid:
|
Grid |
Current Number of Trees |
2023 Number of Trees |
|
1 |
4,588 |
4,558 |
|
2 |
5,109 |
5,097 |
|
3 |
6,241 |
6,249 |
|
4 |
4,932 |
5,072 |
|
5 |
4,146 |
4,428 |
|
Total: |
25,016 |
25,404 |
The City strives to replant all trees that were removed during the prior year, provided they are viable planting sites; however, reforestation is a partnership between property owners and the City. The Claremont Municipal Code requires property owners to water City trees; therefore, if a property owner does not want a new tree, a tree will not be planted because it will likely not be cared for.
Avian Activity
During this reporting cycle, only one nesting bird was reported. The nest was identified in May 2023 in a pine tree, and the tree was not trimmed at that time. WCA staff will inspect the tree again for trimming during the current grid cycle. If avian activity is still present, trimming will be delayed again.
Urban Forest Highlights
Liquidambar Mitigation Program
Approximately 10 years ago, liquidambars began showing signs of Xylella dieback. Xylella fastidiosa is a non-curable disease that affects a tree’s vascular system. The only cure and prevention of further infection is removal of infected trees. When the program began, there were approximately 2,500 liquidambars in the City; currently, there are approximately 960. In years past, reported liquidambar numbers only included Liquidambar styraciflua (American sweetgums), as they seemed to be the most impacted variety. However, in recent years we have noted that other varieties are showing signs of Xylella dieback. The approximately 960 liquidambars remaining in the City include Liquidambar formosana and Liquidambar styraciflua ‘Rotundiloba.’
Each year, the City conducts an assessment of all liquidambars in the City. From this assessment, staff determines which trees require removal. Trees that present 75 percent or greater dieback and trees with dieback in branches greater than 6” in diameter are recommended for removal. Depending on available funding, the threshold for removal is adjusted. Last year, 33 liquidambars were removed, while 45 liquidambars were removed during the previous year. Although Xylella is still present in the City, it is not as prevalent as in years past. This is most likely due to increased watering and routine trimming. The healthier a tree is, the better its ability to fight off disease. Over the next few years, staff anticipates the impact of Xylella on liquidambars will continue to decrease, leading to fewer removals.
Invasive Shot Hole Borer
Invasive Shot Hole Borer (ISHB), once known as the Polyphagous Shot Hole Borer, posed a huge threat to the City’s sycamore and oak tree population. ISHB is an aggressive beetle that bores into trees and introduces a fungus that causes fusarium dieback, much like Xylella, and presents itself as pinholes in the trunk of the tree. In 2019, the City treated a large population of sycamore and oak trees with an experimental treatment. This treatment slowed the spread of the insect and infection in the City, but the City did lose some mature sycamores. Treatment is very costly, so the City did not continue with widespread treatment. Although ISHB activity is less prevalent in the City as in previous years, the City continues to monitor and treat as necessary. This change is likely due to increased watering and awareness. Fewer than five trees were removed due to ISHB in 2023, which is consistent with 2022.
Pine Bark Beetle
A new threat to the City’s urban forest is the Pine Bark Beetle, an aggressive and fast-moving insect that feeds on the cambium layer of a pine tree, causing the tree to die back rapidly. Pine Bark Beetle activity increases during the warmer months. Treatment is available, but usually by the time symptoms appear, the tree is too far in decline. The best mitigation practice is to remove an infected tree immediately to prevent further spread. Over the past year, the City has removed seven pine trees due to the Pine Bark Beetle, which is one more than in the previous year.
Tree Policies and Guidelines Revision Update
In July 2023, the City Council entered into a professional services agreement with Dudek to review and revise the Tree Policies and Guidelines Manual. Since the adoption of the Manual in 1997, only minor changes have been made. These revisions have addressed climate change, monocultures, nursery stock challenges, and pest/disease treatments. Much has changed in the industry and the community over the past several years, most notably the ongoing drought, the Windstorm of 2022, and increased conflicts between trees and hardscape/infrastructure. Additionally, there has been a shift toward planting more climate-appropriate species.
Dudek reviewed and made initial comments on the Manual in late summer 2023. Over the fall, Dudek and the City held several community meetings to solicit feedback from the community. Topics that were discussed include: transparency with tree removals, avian activity during tree work, and acceptable means to address conflicts between trees and hardscape/infrastructure. Dudek made additional revisions to the Manual, which is currently under review by staff in the Community Development Department, the City Manager’s Office, and the City’s liability attorney. The goal is to release the draft document for a 30-day public comment period by mid-May 2024.
Looking Ahead
The 2022-2024 budget includes funding to move from a seven- to a five-year grid trimming cycle. More frequent trimming allows trees better to adapt to the rigors of the urban environment, promotes healthy growth, reduces damage during storms, and reduces risk of failure and decay. The second of the new five-year grid trimming cycle is almost complete. It may take a few years to realize the benefits of the more frequent trimming cycle; however, a five-year cycle is more in line with industry standards, will lead to a healthier urban forest, and will reduce City liability.
Water bags are a cost-effective, responsible means of watering young trees. Each newly-planted tree receives a water bag, and this process will continue. Water bags should only remain in place for the first 1-2 years after planting. Leaving water bags on too long can lead to increased chance of disease transmission and choking of the tree. Over the past year, staff began working with property owners to remove water bags that are no longer an adequate or appropriate means of watering. Staff will continue this process as part of their day-to-day operations.
Over the past several years, the City has planted 15-gallon-sized trees as a requirement of grants the City was awarded for tree planting. Staff looked into the feasibility of moving back to the standard 24”-box-sized trees during the 2024 Reforestation Program, because 24”-box trees are slightly larger in size and more mature. The cost for planting a 24”-box tree has almost doubled in cost. This increase is strictly caused by increased nursery stock costs. Due to budget limitations, we are unable to move back to the standard 24”-box-sized trees.
Take-Aways
The shorter trim cycle and proper pruning of trees again helped to mitigate storm-related tree issues. Unlike in years past, over the last two years we have seen fewer than five trees lost and very few branch failures during the winter season. The City’s urban forest staff were again able to address tree-related issues this winter without the need for outside assistance. Prior to last year, all routine maintenance activities were halted during storm events to address downed trees and branches.
The past two winters have shown record rainfall, which greatly helps to reduce the effects of the drought. However, large amounts of rain cause trees to push additional growth. This leads to clearance issues and heavy canopies, which necessitates additional trimming. Additional trimming increases costs. The cost for additional trimming will be included in the next budget cycle.
Healthy, well-maintained trees are better equipped to fight off disease and infections, more so than stressed and declining trees. In addition, a healthy, well-maintained urban forest leads to fewer liability claims for property damaged by downed trees and branches. It is imperative that the City maintain a healthy urban forest, and as the City moves forward with urban forest maintenance, staff strives to maintain a quality urban forest with great focus on responsible planting, proper care for young trees, and sensible preservation of the aging forest.
CEQA REVIEW
This item is not subject to environmental review under the California Environmental Quality Act (CEQA).
COUNCIL COMMITTEE/COMMISSION REVIEW
On April 17, 2024, the Tree Committee unanimously approved that the Community and Human Services Commission receive and file this report. An excerpt of the draft minutes from the meeting are attached.
PUBLIC NOTICE PROCESS
The agenda and staff report for this item have been posted on the City website and distributed to interested parties. If you desire a paper copy, please contact the Community Services Department.
Submitted by: Prepared by:
Jeremy Swan Cari Dillman
Community Services Director Community Services Manager
Attachment:
Excerpt from the Draft 04-17-24 Tree Committee Meeting Minutes