Ian McHarg, too, was concerned about unrestricted developement. The idea that some developments are more suitable to some landscapes than to others seems only common sense, but when homes built on floodplains are inundated, or hotels built on cliff tops fall into the sea, the extent of human folly becomes evident. We could avoid such calamities and live more harmoniusly whit nature, thought McHarg, if we took natural processes and values into account. He proposed a method for bringing everything into the picture. Known as ‘landscape suitability analysis’ or sometimes just as ‘sieve-mapping’, the technique he developed involved layering information on acetate sheets. So, for example, in considering the optimal route for a new highway, McHarg would combine layers showing the engineering properties of the substrates with layers showing productive soils, significant wildlife habitats, important cultural sites, and so on. When these were combined, it was the areas which were clearest of symbols that were the better areas in which to construct the road. The method also worked” well for planning development at a regional scale. Typically, after gathering physiographic, climatic, and geological data, McHarg could produce suitability maps, usually zoned for agriculture, forestry, recreation, and urban development. The method, which relied on extensive gathering and manipulation of data, became much easier with the growing availability of computers, and ‘McHarg’s Method’ became the basis of the technology known as GIS (Geographical Information System) which uses digital map layers instead of superimposed drawings.
Some years later, however, another nail in the coffin of the designed landscape was drilled: the publication of Ian McHarg’s Design with Nature, which cited the natural world as the only viable model for landscape architecture. This text provided landscape architects with both an analytical method and sufficient moral grounds to avoid almost completely decisions of form and design -that is, if design is taken as the concious shaping of landscape rather than its stewardship alone. McHarg emphasized the evolving study of natural ecology and remained within the bounds of natural processes and planning. A strong moral imperative underpinned the discourse; it mixed science with evangelism -a sort of ecofundamentalism. In his writtings and lectures, McHarg took no prisoners and allowed no quarter.
Ian McHarg, Minimum Social Cost Alignment of a Road (late 1960s)