NZ Visual Diary - entry 458

streetscape in sepia

I was walking north on Queen Street on my way back to my apartment, having been to the central branch of Auckland Libraries to collect a book. It was mid-afternoon and the west side of Queen Street was bathed in the harsh light of the day. The tonal contrasts of that sharp light on the mature trees along the west side of the street were striking.

Few features, built or natural, on the walkways of a city street appear to me as powerful and inviting as that of mature trees.

I queried Claude to prepare a brief history of the urban tree movement in European cities, New Zealand having been colonised by a European nation. I reproduce below that short essay for those inclined to explore the topic.

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A Brief History of the Urban Street Tree Movement in European Cities

From military ramparts to climate-resilient canopies

The tree-lined street is so familiar a feature of the European city that it is easy to forget it was invented. Street trees did not simply grow where cities happened to be; they were deliberately planted, and the reasons for planting them changed dramatically over four centuries — from military engineering and drainage, through royal display and public health, to today’s climate adaptation. What follows is a short account of how the urban street tree became a movement.

^{Medieval beginnings: trees against the enemy}

Before the seventeenth century, European streets were largely treeless. Medieval streets were narrow, crowded and intended for pedestrians and carts, leaving no room for trees, while what greenery existed clustered in churchyards, monastery gardens and market squares. The decisive change came, unexpectedly, from warfare. As siege artillery grew more powerful in the sixteenth century, military engineers in cities such as Antwerp, Amsterdam and Strasbourg began replacing vertical stone walls with massive sloping earthworks — bulwarks — that could absorb cannon fire. To stop these mounds from eroding, engineers planted rows of trees along their length.

The by-product of this military necessity was a pleasant, shaded walkway atop the ramparts, ideal for promenading in peacetime. The very word boulevard descends from the Dutch bolwerk and Italian baluardo, both meaning bulwark. The European street tree, in other words, began life as fortification.

^{The Dutch innovation: trees as infrastructure}

Amsterdam was arguably the first European city to plant trees on a large scale. From the late sixteenth century, as the city dug its famous ring of canals, it planted lindens — and later elms — along each newly cut waterway. This was not primarily decorative. The trees’ roots helped bind and strengthen the soft canal banks, and they were believed to act as natural pumps, drawing water out of the swampy subsoil on which the city was built. They also softened the stench of the canals and the squalor of the streets. By the eighteenth century, elms, which tolerated harsh urban conditions better, had largely replaced the lindens. The Dutch model established a lasting idea: that street trees were a form of civic infrastructure, not merely ornament.

^{The French grand manner: the avenue and the boulevard}

In France, street trees became instruments of display and grandeur. In 1616 Marie de’ Medici, the Italian queen of Henri IV, had the Cours-la-Reine laid out beside the Seine — a wide carriageway flanked by four parallel rows of elms, created expressly for fashionable promenading. Later in the century, under Louis XIV, the minister Colbert and the landscape architect André Le Nôtre extended this taste for formal, tree-lined avenues into and around the capital, planting grand approaches that echoed the drives of aristocratic country estates.

The culmination came in the mid-nineteenth century. Under Napoleon III, Baron Georges-Eugène Haussmann cut long, straight, broad boulevards through the medieval fabric of Paris, bringing light and air to overcrowded quarters. These new arteries were planted on a vast scale — Haussmann’s administration is credited with adding on the order of hundreds of thousands of trees to the city. Haussmann’s Paris became the template that cities across Europe and beyond sought to imitate, cementing the tree-lined boulevard as the signature of the modern metropolis.

^{The nineteenth century: public health and the reforming city}

Industrialisation gave street trees a new rationale. As nineteenth-century cities filled with smoke, filth and dense populations, reformers came to see trees and parks as remedies for the physical and moral ills of the industrial city. Trees were valued for shade, for filtering foul air, and for offering ordinary people access to something of nature within the crowded city. This period saw the founding of municipal parks and the beginnings of organised civic effort — societies, associations and city authorities — devoted to planting and caring for urban trees. It is here that the scattered practice of planting trees begins to resemble a movement.

^{The twentieth century: decline, science and revival}

The twentieth century tested Europe’s urban trees. Two world wars, the pressures of motor traffic, road widening and post-war reconstruction all took their toll, and diseases — most notably Dutch elm disease — devastated species that had defined cities such as Amsterdam and Paris. At the same time, the practice of caring for city trees became more professional and scientific. The term urban forestry — treating all the trees of a city as a single managed resource — emerged in the 1960s and gradually took hold in Europe, bringing an integrated, strategic approach to planning and managing urban trees for their environmental, economic and social benefits.

^{Today: the tree as climate infrastructure}

In the twenty-first century the street tree has acquired perhaps its most urgent role yet. Faced with rising urban temperatures, heatwaves, flooding and biodiversity loss, European cities increasingly regard trees as one of the most effective nature-based solutions available: cooling streets, absorbing stormwater, cleaning air and supporting mental and physical health. The COVID-19 pandemic sharpened public appreciation of accessible green space still further. Cities now pursue explicit canopy-cover targets and diverse, climate-resilient planting — even as the same warming climate stresses the trees themselves through drought, pests and disease.

Across four centuries the European street tree has been, by turns, a defence against cannon, a prop for canal banks, a symbol of royal power, a cure for industrial squalor and a tool of climate survival. Its history is, in miniature, a history of what Europeans have most feared and most valued in their cities.

^{Selected sources}

Orion Magazine, “The Peculiar Relationship Between City Trees and Medieval Battle”; DeepRoot Blog, “History of Street Trees in Holland” and “History of Street Trees in Paris”; Smart Cities Dive, “History of Street Trees in Paris: The Golden Age of the Boulevard”; Arnold Arboretum (Harvard), “How Trees Were Urbanized”; Forest History Society, “History of Urban Forests”; Springer, “A History of Urban Forests and Trees in Europe”; Forest Information System for Europe (EEA), “Urban forestry: multi-functional greening in the city.”