• Davide

Ecology and Urbanism. Part 3.

Where we meet the absolute hero-est of them all, Ian McHarg.


Ian McHarg virtually created the discipline of environmental planning. His work is part of research for an alternative cultural approach to the dominant dichotomy of economic development vs equality and nature. First, Patrick Geddes and then his pupil Lewis Mumford had pursued a "third way" for urban development: "the city as a polis in harmonious relationship to the organic complexity of the regional ecosystem" (Steiner 1997, 57). The historical relationship between morphology, ecology and the social production of space, which Geddes exemplified with the phrase work, folk, place, and which Mumford had described in his historical evolutions in "The Culture of the city" (Mumford), are translated with a particular emphasis on environmental dynamics in McHarg's work.


The valley section ties the different types of landscape to types of settlement.
Patrick Geddes's Valley section. Worth an entire new post.

An evolution of the valley section, Ian McHarg's section of a residential settlement proposal.

After World War II, Ian McHarg elaborates a theory of ecological planning, reusing and systematising the different traditions of American landscape architecture and inheriting the research program of regional planning and social ecology from his mentor Lewis Mumford. McHarg embodies the combination of two almost opposite approaches to the relationship between society and nature: he is an ecologist, an activist who takes it upon himself to disseminate ecological knowledge through radio and television broadcasts; and a landscape planner and designer, attentive to the relationships between urban space, quality of life, economic development. The condition of the human being in the modern city, in continuity with the idea of ​​sanitation, is described in terms of disease, which McHarg defines as the inability of the urban habitat to adapt to the physiological needs of the inhabitants. McHarg's theoretical contribution is based on pragmatic considerations of the usefulness and effectiveness of an interdisciplinary knowledge that allows to verify the results of transformations, as opposed to the irrationality of choices guided by the exclusive speculative interest: a critique that extends to the ordering of daily life, to individual consciences and to cultural and religious debate. In designing with nature (1967), McHarg elaborates a complex theory on the relationship between man and the environment through the development of ecological concepts that are declined in a socio-spatial and philosophical sense at the same time. One of the thought experiments in the volume describes an imaginary space capsule that should have brought a man to the moon using the least possible amount of resources: sunlight, water, bacteria, and algae. The capsule is a limited ecosystem, where oxygen, nutrients and waste must be continuously reused and renewed to allow the astronaut to survive.

Reporting in spatial terms the evolutionary theories of succession and flows of matter and energy, McHarg describes two possible forms of evolution of ecosystems: the entropic or destructive one, through which the energy introduced into the system progressively degrades as the disorder increases; the creative or negentropic one, in which the energy supplied is transformed into increasingly complex and varied systems, therefore more and more ordered and in dynamic equilibrium. This last type of evolution characterises ecological systems: «Energy is temporarily trapped; it will inevitably be dispersed in entropy, but it will also be replaced. Meanwhile, living creatures […] cause matter to rise to higher orders" through the work of plants, first, of other organisms later.

Planning as a form of evaluation.



Staten Island, maps and overlays.

McHarg's devised a method to understand the how the landscape works, how it has affected and can affect societies and cities, and how to design new development. The method uses overlay mapping: superposition of maps describing different aspects of the landscape to extrapolate new information. The succession of layers is chronologically ordered: geologists and climatologists identify the longer-term processes that had defined the geomorphological structure; hydrologists describe the surface and groundwater cycles that feed biological life, represented by landscape ecologists and botanists; finally, historians, sociologists and urban planners have at their disposal the tools to understand the characteristics of each site and the conditioning they had exercised on settlement dynamics. Combining the data, McHarg was able to recognise the hidden differences in the landscape and identify the suitability for development of each area. McHarg called this method ecological determinism. Only after investigating the full scope of the natural-social relationships can the ecological designer start her creative work.

Ecological determinism goes both ways: on the one hand it allows to suggest how we should intervene in the territory; on the other, it highlights the historical links between nature, social evolutions and the social processes of production of space. Like never before, the agency of nature is made evident: performing functions of protection, nutrition, sustenance and ecological balance on which cities depend. With the increase in the possibilities of movement and choice of settlement environments, according to McHarg, even human ecologies tend to become more and more specialised: man adapts in different forms: "man-nature" is different in every place, "There is the morphology of man-Piedmont, man-Coastal Plain [...]" and so on.

The Valleys

The plan for the Valleys, an area under development north of Baltimore, is a classic example of applying this design process. The brief involved the construction of a typical American suburb: economical and efficient design of the infrastructural network, private gardens, and urban sprawl. Based on geological, hydrological, ecological investigations and overlays, McHarg classifies the landscapes of the area according to their availability for urbanisation: the result is an organic diagram that highlights above all the piedmont areas, more stable and less fertile, but which widens, with less intense gradations, even on some scenic slopes. The design proceeds through the definition of three transformation scenarios: the disordered one that had been foreseen maximises spatial dispersion and fragmentation; a second, linear one, concentrates the development along the existing transport arteries, thus saving the entire territory of the Valleys; finally, the proposed scenario is composed of different urban ecologies, laid out to minimise the impact of infrastructures and the built-up area, while taking advantage of the scenic and ecological services of the valleys. The difference in quantitative terms between the three schemes is zero; the difference in environmental, and creative terms is fundamental. The project suggested increasing the population density in the most suitable areas to preserve the most fragile ones. A diversity of settlement types allows to calibrate density and impact the land's conditions while allowing for the colonisation of almost all areas. The result is a complex settlement composed of some centres equipped with public spaces and collective buildings, vast suburban areas that occupy mainly the highlands, and more dispersed houses and services in the wooded areas.



Bird's Eye view of the proposal for The Valleys.





After this long introduction, you might want to meet the man. Here's Ian McHarg:










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