Tree Canopy Patterns and Mortality: How Green Spaces Shape Urban Health

Redacción HC
12/05/2025

Can the way trees are arranged around your home affect your risk of dying from natural causes? According to a groundbreaking study involving over six million adults in Switzerland, the answer may be yes. Published in The Lancet Planetary Health, the research goes beyond traditional green space metrics and investigates how the configuration—not just the amount—of residential tree canopy impacts mortality risk.

This population-scale study reveals that cohesive, well-connected tree cover is associated with lower mortality, while fragmented and irregular tree patches may actually increase risk. With urbanization accelerating and climate challenges intensifying, this research offers timely insights for city planners, public health officials, and anyone interested in building healthier urban environments.

Why Tree Configuration Matters for Health

Urban greenery has long been linked to better health outcomes—lower stress, cleaner air, cooler temperatures, and greater physical activity. But this new research asks a more nuanced question: Does the spatial arrangement of trees matter just as much as how many there are?

The study's authors evaluated five key aspects of tree canopy structure:

1. Cover percentage (how much area is tree-covered)
2. Aggregation (are trees clustered together?)
3. Connectivity (do tree patches form continuous corridors?)
4. Fragmentation (how many separate patches exist?)
5. Complexity of shape (are patches compact or irregular?)

By examining these spatial characteristics, the researchers shed light on how ecological design influences human health—an issue increasingly relevant in our urbanized world.

Study Overview: Mapping Trees and Mortality Across Switzerland

A National-Scale Longitudinal Analysis

Researchers analyzed health and environmental data from 6,215,073 adults in Switzerland, aged 20–90, using the Swiss National Cohort from 2010 to 2019. Tree canopy data came from 1×1 meter resolution satellite imagery, measuring greenery within a 500-meter radius of each person’s home.

Mortality from natural causes served as the primary outcome. Statistical models adjusted for key confounders, including:

• Age, sex, and socioeconomic status
• Air pollution (PM10 levels)
• Urbanization and ambient temperature

The study also tested whether effects varied under different environmental stressors—like pollution or high urban density.

Key Findings: The Shape of Trees Affects Life and Death

1. Tree Cover Saves Lives—But Only Partly

An increase in tree cover by 12.4% (interquartile range) was linked to a 2.1% lower risk of death from natural causes (HR 0.979; 95% CI: 0.975–0.983). While important, this was just the beginning.

2. Aggregation and Connectivity Offer Stronger Protection

• A 6.3% increase in aggregation (more compact, continuous tree patches) was linked to a 17% lower mortality risk (HR 0.831; 95% CI: 0.823–0.840).
• A 2.9% rise in connectivity also reduced risk, though less dramatically (HR 0.946; 95% CI: 0.938–0.953).

“Highly aggregated and connected tree cover seems to maximize health benefits,” the authors explain. “[It] may improve air quality and reduce heat stress more effectively.”

3. Fragmentation and Complexity Increase Risk

• Fragmentation—211 extra tree patches per 100 hectares—correlated with a 7.3% increase in mortality risk (HR 1.073; 95% CI: 1.066–1.080).
• Complexity—more irregular tree shapes—was associated with a 9.4% higher risk (HR 1.094; 95% CI: 1.089–1.100).

4. Worst-Case Scenarios Combine Risk Factors

People living near tree canopy that was sparse, fragmented, and geometrically complex faced up to a 36.6% higher risk of death (HR 1.366; 95% CI: 1.343–1.390) than those surrounded by cohesive, simple tree configurations.

Why This Matters: Practical Implications for Cities and Public Health

Designing Urban Forests for Maximum Impact

The findings highlight the need for strategic green space design:

• Planting trees is not enough—they must be grouped and connected.
• Urban forests should form continuous patches, not isolated fragments.
• Avoiding over-fragmentation and geometric complexity could enhance health outcomes.

These insights are particularly important for urban centers facing high pollution or heat, where the health benefits of greenery are most critical.

Equity and Climate Resilience

The protective effects of cohesive tree canopy were strongest in areas with elevated PM10 levels, higher urban density, and warmer climates. This suggests urban tree planning could be a tool for reducing health inequalities.

“Structured canopy may buffer environmental stressors,” the study notes, “especially in disadvantaged urban neighborhoods.”

What’s Next? Turning Research into Action

The authors call for:

1. Guidelines on ideal canopy configuration for health outcomes.
2. Replication studies in other countries with different urban forms.
3. Integration with climate and health policy, particularly in vulnerable urban zones.
4. Urban experiments to test canopy structure interventions in real time.

They also stress that further research is needed to understand why structured canopies are beneficial—whether through cooling, pollution reduction, noise buffering, or encouraging physical activity.

Conclusion: Not Just Green, But Well-Designed Green

This study offers compelling evidence that urban tree canopy design can save lives. Beyond simply adding greenery, cities must consider how trees are placed, shaped, and connected. The difference between scattered patches and a well-organized canopy could mean a 36% difference in mortality risk.

For policymakers, architects, and urban designers, this underscores a shift in thinking: from quantity to quality—from greening cities randomly to doing so intelligently, equitably, and sustainably.

The path to healthier cities may just begin with planting trees—but the pattern of planting is what matters most.

Topics of interest

Health