Jill in front of King Elmer in Lanesborough, Mass.

Jill Jonnes

Author of “Urban Forests: A Natural History of Trees and People in the American Cityscape”

JILL JONNES is an author and historian, with a Ph.D. in American history from Johns Hopkins University, whose books tell the stories of visionaries who developed and integrated new kinds of infrastructure into cities. In “Urban Forests” Jonnes writes about the people who created lush urban tree canopies, and the trees they introduced — what we now understand to be green infrastructure. As Jonnes learned how essential trees are to city living, she founded the Baltimore Tree Trust and is very proud of that, as the organization has already planted more than 1,000 street trees in once-barren neighborhoods.

What led you to want to write a book about urban forests?

Knowing that almost 80 percent of Americans live in cities, and with climate change upon us, I felt we all needed to know the story of our urban forests. After all, trees in cities are one of the few ways to cool the air. Most of us are very aware of the built urban environment, but we experience the equally important grown urban environment intuitively. And, as we now know through accumulating science, urban trees do far, far more than create shade. City trees are outstanding multitasking civil servants: saving energy, cleaning polluted air, absorbing storm water, raising property values and, I suspect, most importantly, promoting human well-being. And, equally important, they make our cities beautiful. So, my goal was to tell the history and stories of the urban forests that surround us and open people’s eyes, but most of all, to inspire citizens to activism.

What do you think is the biggest issue facing urban forests today?

The fact that too many urban experts — including environmentalists — have never even heard the phrase “urban forests.” They are not aware of the ground-breaking science that shows all the “ecosystem services” that urban trees deliver. Nor are they familiar with the growing body of public health research that confirms how essential trees are to human well-being. Until those who plan, design, build and maintain cities recognize the vital importance of trees and nature in the cityscape, trees will always be an under-funded afterthought, rather than the integral part of cities that they should be. After spending eight years working on my book, “Urban Forests,” I have concluded that we do not need just to plant more trees, we actually need to start pulling up concrete and retrofitting our cities with nature.

If you weren’t an author, what would you be? Why?

I started the nonprofit Baltimore Tree Trust, and I quite enjoy the organizing work in the neighborhoods where we plant trees. Like all local green groups, we have numerous partnerships and those are very gratifying. So, perhaps my nonauthor self would have been a green activist.

What is the most surprising thing that you have learned or discovered while working on your book, “Urban Forests”?

How few of us know that a major tree extinction in going on. Since 2002, the Emerald Ash Borer has spread from Michigan to another 34 states, killing hundreds of millions of native ash trees. Arborists expect that, in time, the ash borer will cross the Rockies, spread to the remaining states and wipe out all the nation’s ash trees. To prevent further such tragedies, a group of forestry scientists are proposing legislation called Tree-SMART Trade that would end all use of wooden pallets in global trade. IKEA already uses only paper, so it is a doable change.

Jill planting on N. Linwood Avenue in Baltimore.

Do you have a favorite story from your time writing the book?

Yes! One of the most endearing and charming of the early tree evangelists was the U.S. Forest Service’s Plant- Explorer-in-Chief David Fairchild. He and his wife Marian Bell (daughter of Alexander Graham Bell) had a home on a big piece of land they called “In The Woods” up Connecticut Avenue in Washington, D.C. There, they delighted in growing some of America’s first Japanese ornamental cherry trees and many rare tree specimens brought back by famed China explorer Frank Meyer and others. I just assumed their home and gardens had long since disappeared to development. But, a Forest Service research librarian informed me otherwise.

The Japanese-style house and the immediate garden are now an oldfashioned nursery school. With permission, I arrived very early one lovely April morning, before the children arrived for school, and wandered the quiet grounds. I had no trouble imagining Fairchild here enjoying his botanicals wonders: Towering old Yoshino cherry trees were in clouds of bloom, while with each further foray beyond the house I encountered another rarity (all had small ID plaques): a Turkish cedar from 1909, a Chinese dove tree from 1906, an oriental oak from 1910, and a magnificent Nikko maple planted in 1908. Of course, Fairchild is long gone, dead more than 60 years. And yet, here were his arboreal treasures shading his house and the happy games of a new generation. A lovely experience.