10 Reasons Why We Should Cut Down Trees — What ISA Arborists Check First

10 Reasons Why We Should Cut Down Trees — What ISA Arborists Check First

"ISA-certified arborists assess removal necessity using a structured decision process that typically includes: structural failure, disease, deadwood, problematic lean, storm damage, root conflicts, and proximity hazards."

Tree removal is the last option — but the wrong tree left standing causes property damage and endangers lives.

"In Vancouver and the Lower Mainland, tree removals typically require a municipal permit and are often subject to certified arborist assessment, depending on tree size, location, and local bylaws."

"High-risk tree work in BC must comply with WorkSafeBC regulations, which typically require a qualified hazard assessment before work begins."

TL;DR

• Tree removal is never the first choice.
• Structural failure is the leading cause of tree removal in urban environments.
• Not every storm-damaged tree needs to come down.
• Fungal conks on the trunk or base of a tree are a diagnostic tool for arborists.

Why Do ISA Arborists Recommend Cutting a Tree Down?

Tree removal is never the first choice.

Arborists spend years learning how to save trees. Pruning. Bracing. Soil treatment. Root zone management. We exhaust those options first.

But some trees reach a point where removal is the only responsible call. The danger is too high. The tree can't be made safe. Or it's already dead.

This article covers all 10 reasons — the specific conditions an ISA-certified arborist looks for before recommending removal. These aren't opinions. They're assessment criteria grounded in ANSI A300 standards and WorkSafeBC regulations.

A Real Example: When Removal Is the Only Answer

In 2024, a Vancouver homeowner in Kitsilano called us about a mature Norway maple in their backyard. The tree was 45 feet tall, with a dense canopy overhang above their deck and driveway.

On inspection, we identified multiple removal triggers: the tree had two co-dominant stems at the main junction (included bark visible), a 3-meter lean toward the house after winter windstorms, and shiny brown shelf fungi at the root collar — Ganoderma, indicating white rot at the base. The homeowner had recently trenched the yard for a sewer repair, severing at least one major structural root.

This tree wasn't just a single problem. It was a combination: structural defect + new lean + active decay + recent root damage + high-value target (house). No pruning or bracing would address the compound risk. Removal was the correct call. Within 48 hours, we removed the tree, ground the stump, and documented the work for the city. The homeowner got a follow-up assessment 6 months later — the root zone was stabilizing, and we recommended replanting with native species (Western red cedar, a natural fit for that site).

That same combination of factors — structural defect + decay + proximity to a high-value target — frequently appears in our removal assessments. Here are the 10 reasons we see most often.

Reason 1: Structural Failure — When Does It Mean a Tree Must Go?

Structural failure is the leading cause of tree removal in urban environments.

It's not always visible from the ground. That's the danger.

An arborist starts by looking for co-dominant stems. These are two main stems growing from a single trunk at a tight angle. Over time, bark gets trapped between them — called included bark. That junction is a weak point. It can fail without warning, even in calm weather.

Next: cracks. A vertical crack running down the trunk is a red flag. A horizontal crack at a graft union or old pruning wound is worse. Open cracks expose wood to moisture and decay organisms.

[IMAGE: Hero photo showing a mature tree with clearly visible co-dominant stem junction and included bark. Alt text: "Close-up of tree trunk showing co-dominant stems with included bark — a structural defect that weakens the junction and increases failure risk."]

The International Society of Arboriculture (ISA) identifies structural defects as the primary factor in tree failures that cause property damage and personal injury in urban settings. "Trees with co-dominant stems and included bark are structurally weaker at that junction and have higher failure rates than trees with a single, well-formed leader — a risk recognized in ISA standards."

A co-dominant stem alone may not trigger removal. Co-dominant stem plus lean toward a structure plus fungal conks at the base? That's a different conversation entirely.

If you see a crack running down the trunk — call an arborist before the next windstorm.

Reason 2: Advanced Tree Disease — How Do You Know When It's Too Late?

Some diseases are manageable. Others are not.

In BC's Lower Mainland, the most common tree diseases arborists encounter:

Armillaria root rot — also called honey fungus. It attacks the root system from the inside out. By the time you see clusters of honey-coloured mushrooms at the base in fall, extensive damage has already occurred. The BC Ministry of Forests identifies Armillaria as one of the most damaging tree pathogens in BC, affecting forest and urban trees across the province.

Bronze birch borer — a beetle that attacks stressed birch trees. Larvae tunnel through the vascular system, cutting off water and nutrients. "Once canopy dieback is severe, recovery becomes unlikely, though the exact threshold depends on the tree species and underlying cause."

Phytophthora root rot — a water mould that thrives in wet, heavy soils. Metro Vancouver's wet winters create ideal conditions. It kills fine feeder roots and can girdle the root crown before any above-ground symptoms appear.

A diseased tree is also a vector. It can spread pathogens to neighbouring healthy trees. Early removal of a diseased tree sometimes protects everything else in your yard.

When disease has reached the root crown and is spreading into the structural root system — that's usually the end of the road.

Reason 3: A Dead Tree — Is It Always a Hazard?

A dead tree is a hazard. The question is how urgent.

Dead wood loses structural integrity fast. Bark falls off. Branches become brittle and dry. The root system stops anchoring the tree to the soil.

WorkSafeBC classifies dead and dying trees as high-priority hazards in any work environment. For residential properties, the same logic applies. Dead trees can fall in calm weather. They don't need a storm.

Here's how arborists confirm a tree is dead, not just stressed:

• No leaves, buds, or new growth for an entire growing season
• Bark peeling in large sheets with nothing green beneath
• Scratch the bark: dead tissue is dry and brown throughout, no green cambium
• Twigs snap cleanly and dry — no flex, no live wood moisture

A stressed tree looks similar in some ways. It may lose leaves early. It may have a sparse canopy. But it still has living tissue. A stressed tree can sometimes be saved.

A dead tree cannot. It shouldn't be left standing near any structure, power line, or area with foot traffic.

[IMAGE: Side-by-side comparison showing a dead tree (bare branches, no foliage, peeling bark) vs. a stressed but living tree (sparse leaves, some green growth visible). Alt text: "Dead tree (left) with bare branches and peeling bark versus stressed tree (right) showing signs of life and recovery potential."]

Professional tree cutting is almost always the fastest and safest resolution for a confirmed dead tree.

Reason 4: Proximity to Structures — How Close Is Too Close?

Location changes everything.

An ISA arborist calculates the "target value" of what sits in a tree's fall zone. A house is a high-value target. So is a deck, a driveway, a vehicle, or a child's play area.

The closer a compromised tree is to a high-value target, the lower the acceptable risk threshold.

Root proximity matters too. "Large trees planted close to a building foundation can develop structural roots that may migrate beneath footings over time, potentially causing foundation stress. The risk distance depends on tree species, root pattern, and soil conditions."

• Foundation cracks and settling
• Drainage disruption from root mass beneath the soil
• Blocked and broken underground pipes

Trees that are otherwise healthy may still warrant removal if the root system has compromised the foundation and the damage is ongoing. Removing the tree doesn't undo the damage, but it stops further root growth and pressure.

Stump grinding is almost always necessary after removing a tree close to a structure. Roots left in place continue to decompose and can create soil voids below grade as they break down.

Reason 5: Storm Damage — When Is It Beyond Recovery?

Not every storm-damaged tree needs to come down.

A snapped branch — even a large one — can often be corrected with proper pruning. The rest of the tree may be completely sound.

But certain types of storm damage are not recoverable:

• Trunk split at a major crotch or union point — the structural integrity is gone
• Partial uprooting — the root ball is lifting on one side. This tree is actively failing
• Loss of 50% or more of the live crown — the tree may survive, but it's now a compromised structure with new co-dominant stems and asymmetrical weight loading
• A new lean toward a structure after the storm — especially combined with any of the above

Environment and Climate Change Canada records show Metro Vancouver regularly experiences winter windstorms exceeding 70–80 km/h. These events consistently expose structural weaknesses that were hidden until the wind loaded the tree.

Don't wait to see what happens next. If a storm-damaged tree is leaning toward a house, fence, or power line — that's an emergency tree removal situation. Call the same day.

Reason 6: Fungal Decay — What Do Shelf Fungi Tell You About a Tree's Future?

Fungal conks on the trunk or base of a tree are a diagnostic tool for arborists.

By the time shelf fungi are visible, significant internal wood decay has already occurred. Fungi don't appear early. What you see on the outside is the late stage of a process that started inside the tree years ago.

> "By the time you see a conk on the outside of a tree, the fungus has been working inside for years — the fruiting body is evidence of decay already well advanced." — Dr. Alex Shigo, Chief Plant Pathologist (ret.), USDA Forest Service; author of *A New Tree Biology*

Different fungi indicate different decay patterns:

Ganoderma — shiny brown or red bracket fungi, often growing at the root collar. Indicates white rot at the base. This is a primary concern for failure at ground level.

Laetiporus sulphureus (chicken of the woods — bright orange and yellow) — causes brown rot in conifers. Brown rot breaks wood into dry, crumbly cubes. Once significant brown rot is present, the wood has lost much of its tensile strength.

Trametes versicolor (turkey tail — small multi-coloured brackets) — indicates white rot in hardwoods. Common on dead wood and declining trees. Less immediately alarming than Ganoderma, but a marker of ongoing decline.

Multiple fungal species on the same tree, or conks combined with a lean and root disturbance, is a high-risk combination that typically results in a removal recommendation.

An arborist report documents fungal decay findings in writing — this documentation is often required by the City of Vancouver and surrounding municipalities before a private tree removal permit is approved.

Reason 7: A Dangerous Lean — When Does It Become a Removal Case?

Trees lean. It's not always a problem.

A wind-trained coastal Douglas fir leans. A tree growing on a slope leans. These can be completely stable.

The risk question is what caused the lean — and whether it's progressing.

Lean with a lifting root ball — you can see raised soil on one side and exposed roots on the other. This tree is beginning to overturn. It can progress to full failure quickly, especially after rain saturates and loosens the soil.

Lean with no root disturbance — the tree has probably always grown at that angle. The root system has adapted. It may be completely stable with no removal risk.

New lean after a storm — even without visible root disturbance, a new post-storm lean means structural loading has shifted. Requires immediate professional assessment.

ISA risk assessment protocols use lean percentage as one variable in the overall hazard rating. A lean of more than 15% from vertical, combined with additional factors — decay, root damage, proximity to a high-value target — typically results in a high-risk rating.

Don't try to eyeball it and draw your own conclusions. Context matters. An arborist brings measuring tools and assessment criteria that a visual inspection from your yard can't replicate.

Reason 8: Vancouver's Tree Protection Bylaws — How Do They Affect Your Removal Decision?

This is where homeowners get stuck.

You can't simply cut down a tree on your property because you want to. Not in Vancouver. Not in Burnaby, North Vancouver, or Coquitlam.

City of Vancouver — The Private Tree Bylaw requires a permit to remove any tree on private property above a certain size threshold. Removing a protected tree without a permit carries fines under the bylaw. Current fine amounts and the full bylaw text are available at vancouver.ca — check there directly, as bylaws are updated periodically.

Burnaby — Burnaby's Tree Bylaw protects trees above a specific size threshold on private property, with different provisions for trees near parks and city property.

North Vancouver (City and District) — both North Vancouver jurisdictions have independent tree protection bylaws and heritage tree designations for significant specimens.

Coquitlam — Coquitlam's Tree Management Policy covers tree removal on private property with its own size thresholds and exemptions.

A certified arborist report is required for most permit applications in these municipalities. The report documents the reason for removal and confirms the tree meets removal criteria under the applicable bylaw.

The City of Vancouver's Urban Forest Strategy sets long-term canopy cover goals for the city. Protecting trees is part of that plan — but legitimate safety-based removals are recognized and processed. The permit system exists to verify that removal is justified, not to block it outright.

A full tree removal assessment from an ISA-certified arborist gives you the written documentation you need for the permit process.

Reason 9: Severe Root Damage — When Has the Foundation Failed?

Roots are the foundation of the tree. Damage them enough, and the tree can't stand — or survive.

Root damage in residential settings typically comes from:

• Trenching and construction — cutting through major structural roots during excavation for utilities, driveways, or additions
• Soil compaction — heavy equipment traffic over the root zone crushing the pore spaces that roots need for oxygen and water exchange
• Grade changes — adding soil over the root zone buries the root crown; removing soil exposes and severs structural roots
• Utility installation — gas, sewer, and water lines routed through the critical root zone

A tree can tolerate losing some feeder roots. Structural roots near the trunk are different. Lose a major buttress root on the side where the tree leans, and you've fundamentally changed its failure risk.

Signs that root damage may be severe enough to warrant removal:

• Sudden canopy wilt without drought or visible disease
• Crown dieback beginning at the branch tips and working inward
• Fungal growth at the root crown following excavation
• New lean after root zone disturbance near the structure

Root damage doesn't always show up immediately. A tree can look fine for a full growing season after major root cutting, then decline rapidly. This delayed crown dieback pattern is well-documented in urban arboriculture literature. If your tree took root zone damage during recent construction, monitor it closely and have it assessed.

Reason 10: Why Do Construction Projects and Invasive Species Justify Tree Removal?

Not all removals are emergency calls. Some are planned.

Construction clearance — A tree in the footprint of a permitted addition, new garage, driveway, or foundation repair may need to come down. In this case, removal is scheduled — not reactive. An arborist report documents that the tree cannot be preserved around the construction zone and supports the municipal permit application. This is orderly work with time to plan it properly.

Invasive tree species — Not every tree belongs in a Lower Mainland urban landscape. Some actively cause ecological harm. Common invasive trees in Metro Vancouver include:

*Acer platanoides* (Norway maple) — listed by the BC Invasive Species Council as a threat to riparian areas and urban forests. It out-competes native maples with dense shade and suppresses understory growth.

*Ilex aquifolium* (English holly) — spreads aggressively through bird-dispersed seeds into urban greenways and natural parks across Metro Vancouver.

*Robinia pseudoacacia* (black locust) — fast-growing and extremely difficult to control once established, with root sprouting that persists after removal.

Removing an invasive tree and replanting with native species — Big-leaf maple (*Acer macrophyllum*), Western red cedar (*Thuja plicata*), or Douglas fir (*Pseudotsuga menziesii*) — improves your property's ecological value and supports the urban forest canopy. The BC Invasive Species Council maintains a current invasive plant list at bcinvasives.ca for reference.

Before You Call an Arborist — What Should You Do First?

A few steps to take before the arborist arrives:

1. Identify the tree species — or prepare a description: bark colour, leaf shape, any cones or fruit present. Species matters for disease diagnosis and bylaw thresholds. 2. Measure the trunk diameter at a standard measurement height — this determines whether a permit is required in your municipality. 3. Take photos from multiple angles — trunk base, crown, any visible decay, any lean. Photo documentation speeds up the on-site assessment considerably. 4. Note what's in the fall zone — is there a structure, fence, vehicle, or power line that could be struck? 5. Check your municipality's tree bylaw — confirm whether your tree size triggers permit requirements before assuming either way.

If the tree is actively dangerous — leaning after a storm, partially uprooted, branches already on your roof — skip the checklist entirely. Call for emergency tree service immediately.

What Happens to the Stump After Tree Removal?

The stump is part of the removal decision.

A stump left in the ground decays gradually over multiple years, depending on species and moisture.

While it decays, it can:

• Host Armillaria root rot, which then spreads to healthy trees nearby through root contact
• Create a tripping and mowing hazard in your lawn
• Continue producing root suckers — cherry, poplar, and Norway maple do this aggressively and repeatedly
• Leave a soil void as larger roots decompose below grade, causing depressions in your lawn

Stump grinding removes the stump to below lawn grade in a matter of hours and turns it into wood chips. The cavity can be filled with the grindings and topped with fresh soil. The area is ready for lawn restoration or replanting within weeks.

For trees removed near hedges or maintained garden areas, grinding is especially important — a decaying stump close to hedging creates ongoing disease and maintenance problems.

It's almost always the right choice when a tree is removed near a structure, active lawn, or high-use area.

Test Your Knowledge

1. In the 2024 Kitsilano case study, what did the shiny brown shelf fungi at the tree's root collar indicate?

• A. The tree was malnourished and could recover with soil treatment
• ✅ B. The tree had active white rot causing internal decay at the base
• C. The tree was infested with insects that required chemical treatment
• D. The tree was in early decline and could be saved with pruning

*The article identifies these shelf fungi as Ganoderma, which signals white rot — a serious structural weakness at the root collar that contributed to the removal recommendation.*

2. What factors determine whether a tree removal in Vancouver requires a municipal permit?

• A. Tree size alone — permits only required for trees above a certain size threshold
• ✅ B. Tree size, location, and local bylaws applicable to that area
• C. All removals require permits regardless of tree size or location
• D. Permits are only needed if the tree is diseased or dead

*The article clearly states that tree removal permits in Vancouver depend on tree size, location, and local bylaws — not a single factor.*

3. According to the article, what is included bark and why does it create a structural risk?

Included bark forms when two co-dominant stems grow from a single trunk at a tight angle, trapping bark between them at the junction. This weak point has higher failure rates because the junction cannot support normal loads and can fail without warning.

4. Name at least two reasons the Norway maple in the case study was recommended for removal.

The tree had multiple critical factors: co-dominant stems with included bark (structural defect), a 3-meter lean toward the house (hazard proximity), Ganoderma fungus indicating white rot (active decay), and recent root damage from trenching (root system compromise). This combination made the tree unsafe to keep standing.

FAQ

What should you know about a Real Example: When Removal Is the Only Answer?

In 2024, a Vancouver homeowner in Kitsilano called us about a mature Norway maple in their backyard.

Reason 1: Structural Failure — When Does It Mean a Tree Must Go?

Structural failure is the leading cause of tree removal in urban environments.

Reason 5: Storm Damage — When Is It Beyond Recovery?

Not every storm-damaged tree needs to come down.

Reason 6: Fungal Decay — What Do Shelf Fungi Tell You About a Tree's Future?

Fungal conks on the trunk or base of a tree are a diagnostic tool for arborists.

Before You Call an Arborist — What Should You Do First?

A few steps to take before the arborist arrives: 1.

What Happens to the Stump After Tree Removal?

The stump is part of the removal decision.