Invasive emerald ash borer has killed 20,000 trees in Hamilton

Hamilton has lost 20,000 ash trees in recent years that were infested by invasive beetles. 

The city is nine years into its 10-year plan to slash the ash tree population, which has been impacted by the emerald ash borer. The city has aimed to remove 10 per cent of the ash trees on public property each year.

The result is "a sad event," said Dan McKinnon, general manager of Hamilton's public works. 

"It's an illustration of some of the new realities that we're experiencing as a result of climate change."

The ash trees have been destroyed over time by the emerald ash borer, which is native to China and eastern Asia. The species has killed millions of trees over North America. 

Forestry staff have been removing the dying trees for public safety. When the city began its plan in 2012, it estimated that the beetle had the potential to destroy the ash tree population by 2020.

But despite the loss, McKinnon said the thousands of trees didn't put a substantial dent in the tree canopy percentage. The canopy cover currently sits at 21.2 per cent. But it hasn't grown either. 

"[We] haven't seen a dramatic change in that over the last number of years. And in some ways that's bad and in some ways that's good," he said at the general issues committee meeting on Wednesday. 

Each ash tree that is removed is supposed to be replaced with a new species of tree. According to a 2020 report, the infestation was so rampant that the city needed to increase the number of trees removed each year to keep up.  

Removals became less frequent in the latter years, the report said, and the city has a 1:1 replacement target.

There were 20,264 trees removed as of 2019 and 13,793 planted in their places. It was estimated that 3,590 would be planted in 2020. 

Staff are working on the update for council and it's expected to be available in the first quarter of 2021, said city spokesperson Jasmine Graham. 

McKinnon said the ultimate goal for the canopy is 30 per cent, "but the reality is we just cannot plant enough trees fast enough."

"You have to plant many, many new young trees before you'll ever achieve the canopy replacement that you lost from that single tree," he said, noting that the trees being removed are big and mature. 

He said the city is in a "decent place," but will look for opportunities to diversify the species that are being planted and get more trees in the ground. As of 2020, there were 40 species being offered for replacement planting. 

The 10-year program costs $2.6 million annually. Removal began in 2013, and the data available ends after 2019.