046 forest city

An average middle-class street in an average Midwestern town. The vernacular architecture here isn't bad, but Hamilton Street would not have not merited a postcard if not for the rows of elm trees on both sides. A century ago, these were the pride of all the towns of southern Michigan.

In the spacious settlements of the New World, people had room to plant trees, and over the years this would become the most distinctive feature of American design. Plenty of towns liked to call themselves the 'Forest City', as Cleveland once did, and devotion to this ideal covered many sins of industrial city-building. The future Argentine President Domingo Sarmiento noticed how it worked in Washington and Baltimore on his visit in 1847: 'All over the city the crowded streets have forests of trees which close off the perspective at a short distance. Above the treetops one can see the cupolas of banks and hotels, the steeples of temples, and the facades of government buildings. There is nothing more spacious, airy and country like than these streets of trees and houses in which the activity of others is a thing which does not need to concern or interest us'.

Sadly, there has always been something in the American soul that does not love a tree. The first fire insurance companies, in Philadelphia, tried to get rid of them all, and refused to cover any property that had one. (That was the origin of the 'Green Tree' company, which liked trees better; their fire marque survives on many of the old homes of historic Philadelphia today). We have seen what happened to the 'Forest City' at the hands of 19th century progress, beginning with the telegraph lines, then the railroads, then the water and sewer lines, the telephone lines and finally the street widenings of the automobile era. Trees declined in quantity, and in quality too. In the old days, developers and property owners were proud to plant avenues of elms, sycamores and chestnuts; after 1945, homes in most new subdivisions only got something like the wretched little Norway maple, selected for compact form and ease of upkeep. Bill Levitt gave his new Levittowners only a wispy sapling, and told them they could plant it themselves. The new strip malls and commercial areas rarely had any trees at all.

This is another tragedy of city-building; nothing adds so much to the quality of urban life. Besides providing shade and shelter from the rain, trees improve air quality; they slow storm water runoff and peak flows, so reducing the need for storm sewer investment. Shading asphalt roads and parking lots, they keep them from becoming 'heat islands' that raise the temperatures of neighborhoods in summer. The national conservation group American Forests recommends a 40% average tree cover for cities: 15% downtown, 25% in urban residential neighborhoods, and 50% in suburbs. They measured tree cover in selected cities, and the results were discouraging: Milwaukee on average had only 18%, Baltimore 31%, Austin 34%, Atlanta 27%. What is more, they found that areas of high tree cover (over 50%) were decreasing everywhere due to sprawl development and the continued attrition of trees in older neighborhoods: down 37% in Seattle from 1972 to 1996, 60% in Atlanta.

Some cities now plant more trees than they lose; others haven't learned yet. We still see trees unnecessarily rubbed out for road 'improvements', following the precepts of the AASHTO manual, and developers still start new subdivisions by levelling them all, instead of using them as value-increasing amenities. Underground parking garages in city squares have become another problem. In European cities, they bury them deep enough so that trees (and fountains) can survive on top. Here, tightwad governments spare that extra expense, and the result has been the ruination of some fine open spaces, such as Los Angeles's Pershing Square. We have suggested that urban design is not brain surgery, and here's an example. There's nothing a city could do to improve itself simpler and easier than planting new trees, and spending some money maintaining the ones it has.

Beyond that, in the fine points of design trees hold a special place. They can help a city perfect its style, like the Sylvester pines of Rome, or the cherry trees of monumental Washington, a gracious gift from Japan. Just a few trees in the right place, or even a single tree can be a memorable design element. We can imagine that the famous olive tree on the Athenian Acropolis, sacred to Athena, was carefully incorporated into that subtle and masterful informal design ensemble in the Periclean rebuilding. Today, every Parisian knows the single weeping willow planted conspicuously at the pointed tip of the Ile de la Cité; they say it is traditionally the first tree to blossom each spring.

Sometimes, trees seem to be the very soul of a town, as with the inevitable, huge old plane trees at the heart of any Greek village. Mediterranean places, where trees may be sparse, have learned how to invest more meaning in the ones they have. Every Greek knows that planes provide the most healthful shade. Hippocrates taught them that, and one of the planes he knew 2,600 years ago survives in the center of Kos, where he had his medical school; it is said to be the oldest in Greece. The planes are for the living. In every village they have their counterpoint in the equally ancient cypresses, symbols of eternity that look down over the cemeteries.

A thousand years ago, in the mosques of Andalucia, ranks of orange trees in the courtyard mirrored the ranks of columns inside. In Seville today, they plant oranges as street trees, and you can pick one and eat it on the city's main street (though out of courtesy to the city few Sevillanos ever do). South Italy has a knack for making a few trees go a long way. The main road across Sardinia, the 'Carlo Felice', is embellished in a unique way. You'll pass a row of four spreading Sylvester pines on one side; then, a quarter mile or so further on, there will be four more on the other side. The arrangement speaks of motion, speed and measured distances; somehow it makes the Fiat you are driving seem like a Maserati. It would be far less memorable if they had lined the road with trees the entire way.

From a little-known Baroque Sicilian town called Mazara del Vallo, out of many lovely open spaces one sticks in the mind: a small rectangular piazza, with simple sandstone palazzi on either side, now home to city offices, their austerity broken only by a little carved decoration around the entrances. The short ends are walled off, with archways, and inside there's nothing but some benches and a row of three small flowering trees, not in the middle, but towards a corner. It's the very picture of the sweet economy design can achieve: a wonderful, minimalist urban room, with a touch of Zen to it.