Overview
Does tree species diversity, in particular native or invasive species, help mitigate flooding incidents?
Geospatial data and historical records can help us understand whether they may be a correlation to the density of native trees and the number of flooding incidents occur in each of Toronto’s wards.
Core Technical Skills
This project required gathering open data from different sources and layering it in Tableau.
Ward boundary data, tree coordinates, and native status all had to be connected on one worksheet.
Project Challenges
Toronto’s wards have been changed over recent years and the boundaries have shifted. This results in challenges drawing and historical trends.
Results
An interactive dashboard which highlights tree species across the wards and their native/ invasive status.
Gathering & Preparing the Data
Sources
- Data was acquired from multiple sources:
- City of Toronto Open Data, Street Tree Data
- Adata set of ~700,000 trees including coordinates, species (latin) name and common name
- City of Toronto Ward Data
- Spatial data for Toronto’s wards
- Native/ Invasive Species Classification
- AI was used to classify the native/ invasive status of all tree species
- Ward Basement Flooding
- Data from 2013-2023 on instances of basement floods per ward
- City of Toronto Open Data, Street Tree Data
- Notes
- Wards were consolidated in 2018 from 44 to 25
- Tree data is not entirely comprehensive, anecdotal testing proves tree are missing
Tree Species’ Spread Across Wards
- There are over 300 species of trees listed in the tree data set across the 25 wards
- However, not every tree is present in every ward with some being very common (in every ward) or very rare (in very few wards)
- To help understand this dynamic, filters were added to:
- Allow individual tree species to be filtered to determine which wards they are present within
- See which trees were commonly occurring or not pre
Native Classification/ Status
Native:
A native species is an organism that lives in a specific region or ecosystem through natural processes and without human intervention.
- Natural Evolution: The species evolved and adapted to the local climate, soil, and other wildlife over thousands of years.
- No Human Transport: They arrived or formed in the area by natural means, such as wind, water, or migration, rather than being brought by humans.
- Ecological Balance: They support local biodiversity and provide food and shelter for other native organisms.
Non-Native
A non-native species is an organism living outside its natural historical range, usually brought there by human activity.
Definition: An animal, plant, or microbe found in a place it did not naturally evolve or arrive at without human help (either on purpose or by accident).
Impact: Not all non-native species cause problems. Many live peacefully in their new environment without harming local nature or human economies.
Also Called: Exotic, introduced, or non-indigenous species.
Invasive
An invasive species is a non-native organism whose introduction into a new environment causes, or is likely to cause, harm to the local environment, the economy, or human health.
Non-native: The organism originates from a different geographic region and arrives via intentional or accidental human activity.
Harmful impact: They outcompete native species for essential resources like food, water, and space, which can disrupt entire ecosystems.
Rapid growth: They reproduce quickly, spread easily, and often lack natural predators or diseases in their new location.
Mapping Trees across Wards
Tree Species’ Native Status Across Wards
- Given there are roughly 700,000 tree records across the city, pin pointing each tree makes made for a busy visualization
- Using AI, I added each species native, invasive, or non-native status
- There were a handful of species recorded in the data set that were “unclear” or “non-native*” which simply meant they were not able to be classified at this time
- The dashboard shows a how invasive species have spread across the city’s wards
Native Tree Species’ Native Status Across Wards
- When filtering for only native tree species, it is clear that they are still present across the wards
- Note the ward background is red for contrast, it is not indicating invasive trees
Native Tree Species’ Native Status Across Wards
- When viewing each ward’s percentage breakdown of its tree’s native status, it tells a different story
- Here we see invasive trees actually make up a smaller percentage of the total number of trees across wards
- Wards 2, 12 and 22 have the greatest percentage of invasive trees
- However wards 7, 10, 13, and 19 have the highest numbers of native trees
Native Status Ward Breakdown
- To help understand the volume/ number of all trees in each ward, this stacked bar chart was created
- Each status (native, invasive, etc.) was assigned a colour and the count of each was added
Flood & Tree Density
Preparation
- Flood data was available for years 2013-2022 however in 2019 Toronto’s wards changed from 44 to 25
- Given this, flood data from years 2019-2022 was used to generate an average number of flood incidents per ward
- The area (km²) of each ward was then captured to calculate flood density using the formula:
- = number of floods/ ward area (km²)
- With the flood density calculated and the area (km²) of each ward captured, ward tree density was calculated using a similar formula:
- = number of trees/ ward area (km²)
Flood & Tree Density
- This charts shows the flood and tree density across Toronto’s wards
- Where flood density is higher per km² the cell is a darker shade of red
- Where tree density is higher per km² the cell is a darker shade of green
- One might expect the higher the flood density the lower the tree density however that is not immediately apparent, wards 5 and 25 both show high flood density as well as high tree density
Flood & Tree Density
- When both tree and flood density are added to a scatter plot, the inverse of my hypothesis is seen.
- Ward-level analysis found a moderate positive association between street-tree density and reported flood density (R² = 0.307).
- This counterintuitive relationship suggests that tree density alone does not explain flood exposure and that other characteristics of the built and natural environment should be considered.”
Flood & Native Tree Density
- Similarly, when viewing native tree density to flood density, the correlation between higher tree density and higher flood incident density is seen.
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