“…it is in the forests that men have grasped the first idea of architecture.”
Francois-Rene de Chateaubriand, Genie du Christianisme, 1802
Old-growth forests are deep and quiet, with their vaulted cathedrals and moss-blanketed groves. In the tradition of Emerson and John Muir, the woods are regarded as sacred areas, places of refuge or escape. Cities are unlike forests: they’re full of change and moving parts. They are noisy and exposed. In the time a juniper or redwood takes to reach maturity, skyscrapers sprout and crumble. But both cities and forests are complex systems, arising from interactions and relationships, spatial and temporal transitions, and emergent properties. Both cities and forests are habitats.
Like a forest is more than a community of trees, a city is more than a community of buildings. A forest ecosystem is rich with smaller plants, insects, birds, and other creatures. So is a city. A forest, like a city, has old neighborhoods and young ones; it has distinct zones determined by height or shade, and property lines maintained by territorial animals. And cities, like forests, have trees.
Urban trees play different roles than their backcountry counterparts. They provide us with shade in the summer and windbreaks in winter; they mitigate the urban heat island effect; they give us clean air and fruit and something to look at. They bring up property values and bring down utility costs. They can grown to be iconic, like Los Angeles’ palm trees or Washington, D.C.’s cherry blossoms. Relative abundance of tree cover hints at the natural forces at work (climate, hydrology, etc.), but can also be an indicator of the social and economic environment. Income Inequality Seen from Space, from Tim De Chant of Per Square Mile, is a stunning example. The first image in each pair shows a satellite view of a low-income neighborhood; the second shows a nearby wealthy neighborhood.
De Chant cites a study that shows “a tight relationship between per capita income and forest cover:”
The study’s authors tallied total forest cover for 210 cities over 100,000 people in the contiguous United States using the U.S. Department of Agriculture’s natural resource inventory and satellite imagery. They also gathered economic data, including income, land prices, and disposable income.
They found that for every 1 percent increase in per capita income, demand for forest cover increased by 1.76 percent. But when income dropped by the same amount, demand decreased by 1.26 percent. That’s a pretty tight correlation.
Trees are expensive: in exchange for aesthetic, environmental, and health benefits, they need space, soil, and sometimes maintenance. They can grow untended, but it takes time. Meanwhile, more modest vegetation flourishes without heed to its social standing or environment. The pictures below are from Santa Fe, New Mexico, near the Railyard district. Even in the high desert of Santa Fe, in parking lots and driveways, a rich urban ecosystem calls for exploration.
Natasha Balwit is an undergraduate student in the Department of Urban Studies and Planning at MIT.