With the devastation to the urban forest wreaked by the emerald ash borer still fresh in the memories of municipal arborists, there’s a new threat to a popular tree species that’s already beginning to make itself evident.
Volatile weather patterns, particularly prolonged periods of drought, are endangering maple trees, Riverside Forester Michael Collins told elected officials during an update on the village’s urban forest earlier this month.
Of the 95 total trees removed from public lands in Riverside in 2021, said Collins, 40 percent were maple trees.
“I consider maples to be a bit of a canary in the coalmine as it relates to climate change,” Collins said. “Maples being a very sensitive species … tend to struggle when we have extreme flooding in the spring and those roots are inundated in saturated soils. And then the pendulum swings with climate change where we go into drought conditions. The ground tightens and it also impacts the roots of these maple trees, and we’re starting to see some significant decline in that way.”
Riverside is not the only place where this threat to maple trees is playing out. Just a short distance away in Brookfield, Village Forester Victor Janusz told the Landmark that of the 157 trees marked for removal in 2021 in that village, 76 of them – 48.4 percent — were maple species.
Silver maples in Brookfield, Janusz said, were particularly hard hit. Between the polar vortex cold temperatures and dry summers in recent years, “I’ve noticed a lot of die-back,” Janusz said.
Unusually wet springs followed by unusually dry summers results in root loss for maple trees, according to Collins.
“It gets really impactful over time,” Collins said. “When you start to lose the roots below ground, you start to shed branches above ground and you’ll see trees with die-back from the top downward.
“If you have multiple events, you really start seeing that decline.”
Last year was “alarming,” said Collins, and he said he expects to continue seeing maples succumb to climate change.
“Previous years I noted some decline, but this is something I’ve been thinking about for the past five years,” Collins said.
According to data from National Integrated Drought Information System, whose website (drought.gov) describes it as “a multi-agency partnership that coordinates drought monitoring, forecasting, planning and information at national, state and local levels across the country,” significant parts of Cook County have been experiencing a sustained period of “abnormal” dryness for much of the past two years.
Between mid-April and July of 2021, some 60 percent of Cook County experienced “moderate” drought, with about 40 percent going through a “severe” drought in May and June.
About 15 percent of Riverside’s public tree inventory are maples, according to Collins. That’s a higher percentage than the inventory of ash trees before the emerald ash borer led to the removal of about 1,000 trees between 2012-17.
The quick loss of virtually an entire tree species has led both Collins and Janusz to seek a more diverse inventory, though maple trees continue to be popular among residents.
While Janusz does not have a full inventory of trees on public lands, he says maples account for a good percentage.
“If there were five to 10 maple trees per block I wouldn’t be surprised,” Janusz said.
Collins said he hasn’t planted many new maple trees in recent years, saying, “Ultimately, my approach is focused on the bigger picture of inventory and species diversity.”
A perfect example of overplanting one species, he said, was found along Akenside Road where the parkway on one side of the street from Northwood to Woodside was planted 100 percent with ash trees.
“We lost an entire half street of parkway trees,” Collins said.
That provided an opportunity, however, in that he replanted the stretch with a variety of trees.
“Every species is now different from the next, so it was making lemonade out of the lemons,” Collins said.