Urban Forests; A Natural History of Trees and People

Urban Forests; A Natural History of Trees and People in the American Cityscape by Jill Jonnes. Viking 2016.

Americans are moving into urban areas in increasing numbers, leaving our wooded environments behind, forest dwellers turned urbanites. And so have many of our tree species.  Jill Jonnes salutes the many “tree huggers” whose concern is helping to preserve these urban forests.

Because of the parallel growth of trade and a world economy, we have been importing wood from abroad mostly for furniture making and wooden crates. No one paid much attention, however, to the various insects and other plagues that accompanied those imports.

The American chestnut (Castanea dentate) is a native of the Appalachian forests. It was devastated by the chestnut blight, a fungal disease, which probably arrived from China. Over three million chestnut trees were destroyed in the first half of the twentieth century. They were once the keystone species of the Appalachia. We roasted the nuts on an open fire. The chestnut was an important food source for white-tailed deer, black bear, and wild turkey.  Its disappearance also was costly to bird populations. Though never an important species in the urban forests, its demise left a huge gap in the upper canopy of our woods.

The American ash (Faxinus americana) was also once an important component tree in the eastern hardwood forests, from Nova Scotia to Minnesota and south to north Florida and across the South to eastern Texas. Favored for furniture and flooring, the ash was widely planted as an urban street tree.

Elms were perhaps the most important tree species in the urban forest prior to their demise in the 1960s. Their loss was deeply felt by many of us who grew up under the shade of a stately elm. They died of Dutch elm disease imported from Holland. Elm burl logs, intended for use as veneer for furniture, contained the Elm bark beetle which hitched a ride. It carried with it fungus spores that quickly found the enormous elms that were so commonly used as street trees. The fungus clogged up the elm’s water-carrying vessels. The beetles moved quickly to the top of the tree where the wind could scatter the beetle to nearby trees.

It should be noticed in all of these cases, the tree species were introduced as a monolythic species. When the disease hit one individual tree, the avenue trees would soon be lost.

There are some happy stories. Cherry trees were imported from Japan, to decorate the Washington Mall. They were the project of Eliza Scidmore, a journalist, world traveler, and tree enthusiast. After a two-year campaign from 1904 to 1906 she got President Theodore Roosevelt to agree to the project. Off and on, plant enthusiasts have gotten assistance from American Presidents. George H.W. Bush urged us all to leave our home, neighborhood, and town better than we had found and suggested our attention to urban trees. Several first ladies also found urban forests to be one of their causes.

Exotics are not, however, a good idea. The Tree of Heaven (Ailanthus altissima) a tree that grew in Brooklyn — and elsewhere — was a highly praised species from China when it arrived via Europe. It was commonly used as a street tree in the nineteenth century because it grows fast and has a considerable spring blooming season. But it is no longer praised for that quality and is, in fact, considered invasive.

The favored sugar maples of Vermont are no longer as spectacular with their fall colors as they once were. That is because the manufacture of maple sugar no longer depends upon clear cutting all other tree species to fuel the process. As those elms, chestnuts, and other trees grow up among the sugar maples, they gradually dilute those wonderful fall colors.

Jonnes argues that if we were to calculate the dollar benefits of trees and particularly urban trees, we might be more willing to trade trees for the endless layers of asphalt and black top that are filling our cities with heat-absorbing, impermeable surfaces. That asphalt with which we lather a good portion of our unbuilt spaces, has the company of our utilities on poles. Utility poles provide neither the shade nor return nutrients to the soil!

Jill Jonnes speaks eloquently of the many ordinary citizens who tend the urban forest. She is equally complementary of the work of professionals from the early plant explorers, to arborists to urban foresters, to botanists, to nurserymen. They continue to remind us that urban forests are an essential element in a city’s infrastructure.



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