Arborists & Urban Futures

Xuebing Du

An article by Clive Thompson we linked to in 2016 makes me wonder why today is the first time we are sharing his work since then. I remember reading a review of his book last year but did not see a fit with the themes we tend to focus on here. Urban trees,  for one example, feature in our pages frequently. And trees more broadly speaking have probably been featured more than any other topic due to our mission. So our appreciation to the Atlantic for publishing this, and an added thanks for the excellent photographic accompaniments:

Trees Are Time Machines

Arborists are planting trees today that must survive decades of global warming. The health, comfort, and happiness of city dwellers hang in the balance.

City trees lead difficult lives. A lot of things are trying to kill them, particularly the trees planted on sidewalks: Tightly compacted soil with high alkaline content makes it harder for them to absorb nutrients. Tiny plots of land admit very little rainwater. They’ve got dogs peeing on them, people dropping cigarette butts nearby, and cars belching pollution.

Xuebing Du

“We’re talking about trees that are very vulnerable,” says Navé Strauss, the head of street-tree planting for New York City. His team manages the planting of new trees on streets and public rights of way; there are more than 666,000 street trees in the city, and the team plants about 16,000 new ones annually. For decades, New York arborists have tended to prefer “tough,” hardy species that thrive well against adversity—such as the London planetree, which sports grayish bark and big, maple-like leaves that offer sidewalks tons of shade.

But lately, Strauss has been looking for trees that can handle an even tougher challenge: climate change.

Xuebing Du

In the past century, the United States has heated up as much as 1.9 degrees Fahrenheit. natural cycle of cities is already being pushed in new directions; in New York, spring now begins a week earlier than in the 1950s. Current predictions suggest that the temperature in the city will rise by up to 6 degrees by the 2050s, and up to 10 degrees by the 2080s. This hotter climate will bring longer periods of drought too. That will require some entirely new trees that can survive, and thrive, in the decades to come.

One stands out: “There’s this crazy tree out in Arizona, where it’s highly, highly dry,” Strauss told me. A few of its relatives, the northern catalpa, have already migrated to New York and thrived, sporting huge leaves and flowers. “You’ll see them growing in vacant lots, where you’d be like—Where’s their food source?” he laughed. That’s why he thinks this new hybrid ought to be able to handle the coming droughts. So he pulled the trigger, and 10 of them went into the ground. Within a few years, Strauss and his team will know whether this tree will be a useful part of New York’s warmer, weirder climate.

Urban foresters think a lot about their cities’ distant future, because when you plant trees, you have to. A well-maintained tree in an urban park can last 150 years or longer. A sidewalk tree lives a shorter period, but it still might get 30 years or more. So a city arborist is always thinking: What’s this city going to be like 20 years from now? Or 50? Or 100? Trees are time machines, connecting us to the future…

 

Read the whole article here.

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