Learn More About Urban Street Trees in the BIA

Curious how many urban street trees are in your area?


Family biking in the future version of downtown St. Catharines. The street are lined with many old trees and lush planters.

Introduction

An urban street tree (UST) is any street facing tree which, collectively, make up a significant layer of an urban forest (UF). The St. Catharines UF is a lot closer to home than you may think. The City of St. Catharines describes an UF as “…the collection of trees and shrubs that are growing within a city. It may contain any kind of woody plant vegetation growing in or around our homes”. Nurturing the UF requires a great deal of care, planning and maintenance. When we invest in trees, and other natural infrastructure, we invest in a Nature-based Solution (NbS) that is proven to build community health & resilience and mitigate various climate change impacts (e.g., heat island effect, flooding, desertification, etc.).

USTs provide a range of benefits & opportunities for the St. Catharines Downtown BIA. Trees are important to the Downtown as they provide much needed shade and beautification & act as important infrastructure (known as green infrastructure). This helps encourage people to stay longer and also enhances the overall experience of being Downtown, increasing the likelihood of return visitors while improving liveability. USTs are a crucial natural asset for the City of St. Catharines, residents, businesses, and everyone else who calls the Garden City home. 

Two young men crossing a street in a future version of downtown St. Catharines enjoying the many old street trees lining St. Paul Street near the performing arts center

Project Background

The tree inventory began with one simple question: how can we bring more trees downtown?

This led to a tree inventory under the direction of the St. Catharines Downtown Association’s
(SCDA) Executive Director, Rachel Braithwaite. Through an internship opportunity with Niagara College’s Environmental Management & Assessment Program, two interns, Aditi Kerawala & Sean Parkinson, were selected to conduct an inventory of the BIA, including an inventory of the existing tree infrastructure. This inventorying process and initial research question was supported by discussions with the SCDA’S Streetscape & Sustainability Committee, comprised of local business owners, community leaders, and the SCDA staff. Around the same time, a motion was put forward by Councillor Matt Siscoe, to plant 100,000 trees over the next 10 years (e.g., average of 10,000/year).

In March of 2022, Lindsay Taylor, Niagara College alumni, was hired as a summer Sustainability Coordinator for the SCDA to expand this research and draft a Tree Report. Working alongside fellow summer Sustainability & Events Coordinator, Sean Parkinson, Taylor drafted a sampling & analysis plan that would enhance the existing tree surveying data and provide a sustainability evaluation of the UST academic literature and popular press (see methodology below). Two new SCDA interns, Poonam Gautam and Lina Garcia, were brought on board to assist with the field surveying and data management.

During this process, the team found that the majority of the USTs downtown were younger, smaller trees. Trees begin providing the community value when they reach a large size and have a dense canopy.

The research question needed to change: how can we ensure that USTs reach maturity?

Tree Report

To Learn More About Urban Street Trees in the BIA Download the Complete SCDA Tree Report

Recommendations

Throughout the research process, various stakeholders from the SCDA’s StreetScape & Sustainability Committee, City of St. Catharines, Niagara Region, Niagara College, Downtown Guelph Business Association and Waterloo’s Asset Management Team provided guidance and feedback on the direction of the following recommendations.

Data Summary

Urban Street Tree infographic for the BIA. Cartoon banner featuring a small town with many street trees. 

First icon displays a stack of money. Text reads UST Replacement Cost. 
It would cost $ 240,859 to only replace the USTs in the downtown BIA. This does not factor other costs and value, socially, economically, and environmentally, associated with street trees. 

Second icon is a cartoon downtown with many street trees. Text reads Urban Forest 
An Urban Forest is the collection of trees and shrubs that are growing within a city. It may contain any kind of woody plant vegetation growing in or around our homes. 

Third icon is a mature tree. Text reads Tree Maturity
Nine trees greater than 50 cm were recorded in 2016. This dropped to six in 2022. 

Next icon depicts two cartoon evergreen trees, CO2 gas, and an arrow pointing down to demonstrate how carbon is captured and stored by trees. Text reads Carbon Storage
Carbon storage plays an important in climate change mitigation. It is measured as the total quantity of carbon stored by USTs based on species, Diameter at Breast Height (DBH) & frequency. In 2022, 31.44 metric tons of carbon was stored by USTs in Downtown St. Catharines. This is down 6.23 tons from 2016.

Next icon is a cartoon broadleaf tree depicting an arrow pointing to the tree with CO2 and an arrow pointing away with O2. This icon is meant to demonstrate how oxygen is produced by trees. Text reads Oxygen Production Gross Amount of Oxygen produced by the BIA street trees. In 2016 & 2022, 2.8 metric tons of oxygen was produced. 

The sixth icon is a honey locust leaf. Text reads Most Common Tree The most common tree in Downtown St. Catharines is a Honey Locust also known by its scientific name Gleditsia triacanthos. 

The seventh icon depicts a cartoon forest with many different species of trees. Text reads species richness the species richness value for USTs in the BIA is 0.77. The closer we are to 1 the more diverse our trees are!

The next icon is a smaller cartoon tree. Text reads Average Size while the average size was 20 cm, the most frequent tree size observed was only 6 cm.

The last icon consists of a cartoon version of a diverse group of people spending time together. The text reads Urban Forest and Community USTs play an integral role in our urban forests. Respecting these important natural assets and allowing them to grow is the best strategy for protecting USTs in the BIA.
Urban Street Tree Infographic

Mapping

The following maps were made using QGIS – A Free and Open Source Geographic Information System.

Map of Urban Street Tree Distribution in 2016
Map of urban street tree distribution in 2022

Methodology

Two Niagara College interns measuring the diameter of an urban street tree.

Field sampling took place every Wednesday from May 18th, 2022, to June 22nd, 2022. This work was conducted by two SCDA interns, Poonam Gautam & Lina Garcia. For each UST within the BIA, the interns would record:

Georeference
Tree Species
Diameter at Breast Height (cm)
Health Assessment

The georeference was recorded in UTM (Projection NAD83 17N) using the UTM/Lat-Lon Android App. To identify the tree species the interns were provided an introductory module on tree identification, introduced to various tree ID apps including iNaturalist and Seek, and relied on John Laird Farrar’s “Trees in Canada” ID book. DBH (cm) was recorded using a DBH measuring tape provided by Trish Haynes through Niagara College’s Environmental Labs. To complete the tree health assessment, the interns assessed 5 qualitative markers including:

Bark Wounds: visible damage to trunk of tree
Codominance: trunk splits into two  
Unbalanced Canopy: canopy is lopsided  
Dead Branches: branches without foliage  
No Annual Growth: branches show no signs of annual growth  

Note: Health Assessment is for reference purposes only. A health assessment should be completed by a certified arborist.

When 4 of 5 markers were present, the tree was deemed a ‘Hazard Tree’. Field sheets were digitised using Excel and stored on the SCDA Google Drive. Further data analyses would include the use of Excel for an in-house statistical analysis & i-Tree for a multi-parameter value assessment.

The in-house analysis focused on classing the trees into four intervals:

Class I: Under 10 cm
Class II: 10 cm to Under 25 cm
Class III: 25 cm to Under 50 cm
Class IV: Greater than 50 cm

These intervals, alongside other general statistics & i-Tree data, were used to establish a baseline for the BIA. This information was then compared to Guelph’s BIA through a benchmarking exercise.

Size Class Intervals

Saplings = Class I (Under 10 cm)
Young Trees= Class II (10 cm to Under 25 cm)
Adult Mature Trees = Class III (25 cm to Under 50 cm)
Large Mature Trees = Class IV (Greater than 50 cm)
 Class Intervals2016 Frequency2022 FrequencyChange from
2016 to 2022
Class I (10 cm and under)7695+ 19
Class II (10 to under 25 cm)10483– 21
Class III (25 to under 50 cm)5372+ 19
Class IV (50 cm and greater)96– 3

Key Values & Statistics

 6.2 cm was the DBH most often recorded in 2022 (i.e., the mode). There is also a low population variance & standard deviation and a left-skewed distribution. These indicators, combined with the data range, describe the UST population as predominantly young trees (e.g., Class I, lower Class II) with fewer making it to maturity (e.g., Class III & Class IV).
Group of friends spending time in the future green version of downtown near James Street and St. Paul Street.

Tree Report

To Learn More About Urban Street Trees in the BIA Download the Complete SCDA Tree Report