Why Tree Diversity Matters in Calgary
The Risk of Monoculture
Calgary’s urban canopy once relied heavily on a few species, particularly elms and poplars. Pests or diseases targeting a single genus can devastate entire neighborhoods. Diversity is insurance against canopy collapse.
Benefits of Diversity
· Resilience to pests and diseases
· Variety in seasonal color and texture
· Improved habitat for birds and pollinators
· Greater adaptability to climate change
Strategies for Increasing Diversity
ISA Certified Arborists recommend the “10-20-30 rule”: no more than 10% of a single species, 20% of a genus, or 30% of a family. Planting underused hardy species such as hackberry, bur oak, larch, and serviceberry helps spread risk.
Calgary Examples
Recent infestations of black knot in chokecherries highlight the danger of over-reliance on one tree type. By contrast, neighborhoods with mixed species maintain canopy even when one group is affected.
Final Thought
A resilient urban forest isn’t about planting more trees of one kind—it’s about planting the right mix. Diversity ensures that Calgary’s canopy thrives for generations.
