Cities are vulnerable to heatwaves. But green spaces can help more than we thought

[hauntedheadnc]

As the climate changes, cities scramble to find trees that will survive

...Urban arborists say planting for the future is urgently needed and could prevent a decline in leafy cover just when the world needs it most. Trees play a crucial role in keeping cities cool. A study published in 2022 found that a roughly 30 percent increase in the metropolitan canopy could prevent nearly 40 percent of heat-related deaths in Europe. The need is particularly acute in marginalized communities, where residents — often people of color — live among treeless expanses where temperatures can go much higher than in more affluent neighborhoods.

While the best solution would be to stop emitting greenhouse gases, the world is locked into some degree of warming, and many regional governments have begun focusing on building resilience into the places we live. Urban botanists and other experts warn that cities are well behind where they should be to avoid overall tree loss. The full impact of climate change may be decades away, but oaks, maples, and other popular species can take 10 or more years to mature (and show they can tolerate a new climate), making the search for the right varieties for each region a frantic race against time.

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To find solutions, researchers are studying which trees could do better than those currently struggling in rapidly warming cities, with an eye toward species that have already adapted to drier regions hundreds or even thousands of miles away. In Canada, for example, scientists have matched trees from the northern United States with the expected climates in cities including Vancouver, Winnipeg, and Ottawa. Urban foresters in Sydney are considering the trees in Grafton, an Australian city about 290 miles closer to the equator.

[sopas ej]

I thought this article was apropos.

From LAist:

We're Hurting Our Trees
Why the practice of "topping" is harmful

By
Fiona Ng
Published May 12, 2024 5:00 AM


A topped tree in L.A.
(Fiona Ng / LAist)

Here's an unassailable fact: Trees are awesome. Among the laundry list of benefits, they provide shade in our increasingly warming weather, they clean the air, prevent soil erosion, reduce noise pollution.

That's not all. "They're good for us mentally, psychologically and socially," said Bryan Vejar, a senior arborist at the environmental organization TreePeople.

Like all good things, trees need to be nurtured and maintained. And for many Southern Californians, a not uncommon sight of maintenance we've seen takes the dramatic form of trees having their canopies and branches cut off.

It's a technique called "topping."

"This is sadly a very common practice.... I should say malpractice, honestly," Vejar said. "Once you notice it and start to understand the hazards and harms of 'topping,' you'll see it everywhere."

Rachel Malarich, L.A.'s forest officer, said topping has indeed become more pervasive.

"I have seen the proliferation of tree topping across our region over the past decade or so," she said. "When I see trees that are cut that way, it is a little gut wrenching."

With trees, less is actually more

The method of topping is hard to kick partly because of simple economy, Vejar said.

"I think people assume that value is equated with volume removed out of a tree," he said. "So if I took out 90 or 100% of the volume out of the tree, you would think, 'Oh wow, what a good value I got.'"

He added that people also mistakenly think that the more you chop off, the longer it'll take for it to grow back.

"Less is more with trees," he said, noting that "it's sort of a vicious cycle of regrowth after over pruning a tree."

The rapid regrowth happens because topping triggers a panic response and sends the tree into overdrive.

"When you top a tree, the physiological response from the tree is to produce a lot of what are called water sprouts," Vejar said.

Those are all the long, thin branches that shoot out from a tree around its stumps.

"When you remove its photosynthetic array, all of its leaves and canopy, you're robbing the tree of its ability to feed itself," Vejar said. "It needs to put out some growth in order to shade the tree and also produce enough photosynthesis to keep the system running."


(Fiona Ng / LAist)

[...]

Link: We're Hurting Our Trees