Western red cedars die off as extended dry spells continue, say experts

Some Western red cedars are struggling after repeated periods of drought and experts say the tree could vanish for good in spots with shallow, dry, rocky soil if current climate patterns continue.

When Nick Page started posting pictures of dead Western red cedars that had turned from verdant green to rust red he was overwhelmed by how many people chimed in or sent more disturbing images.

'Western red cedar is the canary in the coal mine'

Page, a biologist, says this has been long warned and predictions seem to be coming true in many parts of the Lower Mainland. Trees on sunny slopes with poor soil are the first to go.

He points to a stands of Western red cedars planted in Vancouver's Jericho Park in the 1960s that are all drying out and losing their colour.

"Look in Jericho Park you will see these dead cedars. They are 40 or 50 years old and they are not making it through these summers either. They are well established and there is decent soil," he said.

The Western red cedar also goes by the name giant arborvitae, meaning tree of life. It was chosen as B.C.'s provincial tree in 1988 in part to honour its traditional use by First Nations. But 10 years later, in 1998, many were lost after a three-month drought in B.C.

Tree experts have long expected the species to disappear from parts of the province, especially where there's shallow, well-drained soil.

Lori Daniels is with the Tree-Ring Lab at the University of British Columbia. She said narrow rings exposed when a cedar is cut down indicate the dry seasons that are damaging trees.

Long predicted

"Declining red cedars tend to die from the top down.  During severe or prolonged drought, the tree may not be able to access sufficient water through their roots to transport water to the top of the tree where it is needed in the leaves to photosynthesize. As a result, the trees will shed any extra leaves or begin to die from the top down," she said.

Once weakened the trees are also vulnerable to insects infestations and other blights.

"I've been watching this happen for the past 30 years. It's been a slow-motion exercise," said Stefan Zeglen, a forest pathologist based in Nanaimo.

"[Western red cedar] is the canary in the coal mine at this point. It's the first well-known species that's likely to disappear from areas that it's traditionally established in because of a lack of moisture," said Zeglen.

He said the species cannot withstand eight to 12 weeks stints of drought. The lack of water weakens the shallow-rooted tree over time. After a few summers of drought the finer roots are lost and the tree loses its ability to uptake moisture.

"Then the tree just declines and dies," he said.

Zeglen blames climate change that is expected to bring longer dry spells and less winter rain.

He said other vegetation will fill in the spots left behind, but people may be disturbed to see the cedars die.