How climate change, construction can weaken trees and cause severe storm damage 

Last Saturday's severe thunderstorm and strong winds caused extensive damage across Waterloo Region and Guelph.  

Uprooted trees and snapped branches damaged cars, homes, property. In Ontario, nine of the ten people killed by the storm, and its aftermath, died from being struck by felled trees or tree limbs. In one case, a woman in Brant county died when a tree fell on her camping trailer.

A climate expert said trees weakened by climate change conditions and infrastructure projects may be partly to blame for the scale of the damage. 

"Extreme heat and drought conditions can have an impact on tree growth … and can encourage shallow root systems as trees try and make the most of rainfall on the surface," said Joanna Eyquem, managing director of climate-resilient infrastructure at the Intact Centre on Climate Adaptation at the University of Waterloo.

She said rising temperatures have also created ideal conditions for tree diseases like the emerald ash borer to thrive. 

Infrastructure work and road maintenance can also damage a tree's root system, said Eyquem.

"If our trees are less healthy, we're more likely to have dead branches, or trees that are more unstable … So when we see high winds … those unstable trees can fall and … branches can blow off," she said.

Protecting trees during construction

Municipalities say protecting mature trees and natural areas is a priority during construction planning.

A spokesperson with the City of Kitchener said developers and contractors are obligated to work around trees and follow a high standard of tree protection.

"When work takes place within the drip line of a tree, it is done with careful planning and protective measures to minimize tree and root damage," a spokesperson said in a statement to CBC News. 

Jamie Croft, manager of infrastructure engineering with the City of Cambridge, said the city, like others, encourages trenchless technologies, which avoids excavation. 

"The city is aware that root damage within the dripline of a tree contributes to weakened trees and takes the necessary precautions for the protection of trees," said Croft in an emailed statement.

A City of Waterloo spokesperson said that city avoids running utilities and other infrastructure near mature trees whenever possible. If that's not possible, then protection measures are outlined in each contract.

"Trees that are unhealthy or would be too unstable following construction may be removed. When possible, trenchless work is done to minimize damage to root systems of mature trees," said a spokesperson.

Meanwhile, Eyquem said municipalities can take proactive measures to better prepare for future storms, including boosting tree canopy targets and managing trees as if they were assets, such as building infrastructure.

"Long-term planning and investments," she said.