Suzanne's Mom's Blog

Photo: Melanie Stetson Freeman/ Christian Science Monitor
Pruning trees in Baltimore helps to keep them healthy. “We are making a difference,” says Erik Dihle, arborist for the city of Baltimore. … “It ties into social equity, into climate adaption, everything.”

The value of tree canopies in cities is not a new topic at this blog. I’ve written often about efforts around the world to capture the physical- and mental-health benefits of urban forests (for example, in 2014, 2017, and last summer).

I’m not sure, though, that I ever knew how forward-thinking Baltimore has been, a city that was recently disparaged by a kind of leader unfamiliar with actual leadership.

Stephanie Hanes writes at the Christian Science Monitor, “From his headquarters office, Erik Dihle drives into what has become one of the most monitored forests in the United States.

“He begins to point out the trees: There is a tulip poplar, as big as the ones George Washington planted at Mount Vernon. There are the blossoming cherries, with a cotton-candy display that rivals their famous compatriots down the road at the Tidal Basin in Washington, D.C. And there is a white oak, Maryland’s state tree, with its branches gnarling horizontally for yards.

“ ‘This is a good-size one,’ he says, getting out of his truck to pace the area of shade created by the tree’s canopy. ‘I’d be surprised if it was less than 150 years old.’ …

“Mr. Dihle’s forest is in the city. He is the arborist and the head of forestry for the city of Baltimore, which means he monitors all the trees here – those growing in shady parks, in metal grates along busy streets, in backyards, and in relatively untouched forest patches dotting the municipality. Together, these trees make up what is called the city’s ‘urban forest.’ …

“With concern growing about climate change and rapid worldwide urbanization, city forests have emerged as one widely touted solution to a host of social and environmental challenges. Municipalities from Barcelona, Spain; to Melbourne, Australia; to Chicago have put urban canopy coverage at the center of their long-term strategic plans. Community groups focusing on planting, maintaining, and saving trees have blossomed across the U.S. In 2015, the World Economic Forum’s Global Agenda Council on the Future of Cities named increasing green canopy coverage as one of its top 10 urban initiatives.

“Yet at the same time, the U.S. Forest Service, which in the past decade has also upped its focus on urban forests, has found that American cities are losing trees – and quickly. … Urban regions showed a particular decline, along with an increase in what the researchers call ‘impervious surfaces’ – in other words, concrete.

“But not, it turns out, in Baltimore.

“Here, the net tree canopy coverage has increased. Not by a lot, Mr. Dihle is quick to point out – only from 27% of the city’s land coverage to 28% – and not because Baltimore hasn’t lost trees. It has. But overall the tree canopy here has grown, which means that Mr. Dihle has found himself presiding over one of the more successful efforts in the U.S. to preserve and improve the urban forest. …

“New technology has let researchers better understand the urban ecosystem – not just how trees thrive or fail in a city, but how they intersect with humans.

‘[Trees] impact work productivity, wildlife habitats, air pollution removal, carbon sequestration, energy use,’ says David Nowak, senior scientist with the U.S. Forest Service who authored the recent national report on tree canopy loss. … ‘We should be smart about this whole process and use nature to make our lives better.’

Much of the understanding of how, exactly, trees affect everything from climate to criminal justice stems from a technological breakthrough pioneered in Baltimore. …

“By the 1990s, satellite imagery allowed governmental agencies such as NASA to produce visible images of Earth and to show on various scales where trees existed. But there was a limit to those pictures, explains Morgan Grove, a scientist with the U.S. Forest Service who has worked in Baltimore since 1999. Because the data were recorded in pixels, not physical parcels, it was difficult to identify, say, the owner of a particular tree, or to compare what was happening from one city block to another.

“In 2006, though, the Forest Service, working with researchers from the University of Vermont’s spatial analysis lab, put together a new type of land cover map in Baltimore using a combination of aerial imagery, light-reflecting technology, and high-resolution landowner data. This novel approach not only allowed a closer look at trees, it also let scientists synchronize forest maps with other information that was also newly computerized and manipulable – everything from health records to census figures, crime statistics to property values.”

Learn about the amazing array of data they were able to collect, how data helped the city prevent nascent problems like storm sewer overflow, and how the community has organized to protect and expand urban forest benefits, here.

By the way, I thought the photographer on this story, Melanie Stetson Freeman, did an especially good job capturing the faces of these tree huggers. It helps one understand that the individual and the things an individual cares about are what improve the world.