Scale of permanence

What the scale is for

Every piece of land has things that will outlast any plan and things that can be changed next week. The scale of permanence puts them in order. P. A. Yeomans, the Australian farmer and engineer behind Keyline design, worked it out on his farms Yobarnie and Nevallan and set it out in The Challenge of Landscape (1958). His list runs from the most lasting to the most changeable:

1. Climate: rain, temperature, wind, the length of the dry season.
2. Land shape: slopes, ridges, valleys, the form of the ground.
3. Water supply: where water falls, runs, can be held and stored.
4. Roads and access: tracks and paths, how people, machines and animals move.
5. Trees: woodland, shelterbelts, orchards.
6. Buildings: houses, sheds, stables.
7. Subdivision fences: the division of land into paddocks and fields.
8. Soil: its life, its structure, its organic matter.

The further down the list, the less energy it takes to change an element, and the more freely it can be fitted to what lies above. Yeomans drew a planning rule from this: decide in this order, and the farm grows with its landscape instead of against it. A track laid before the water lines are known may later carry runoff like a gutter. A fence drawn on a straight survey line cuts across the natural flow of the slope. A house built in the wrong place fixes the paths of a whole life.

Soil standing last is the surprising part. For Yeomans it was not a given but something good management could build within a few years, once water, access and trees sit in the right places. Permaculture took the scale up early. David Holmgren used Keyline extensively in his designs, and the scale fits his principle design from patterns to details.

How to use it, step by step

Take a notebook, a map or aerial photo of the land, and walk down the list. At each level ask three questions: what is there, what can be changed, and what follows for the levels below?

1. Climate. Collect what is known: rainfall over the year, the dry months, the wind directions, frost or its absence. Then look for the small climates of the site, which can differ markedly from the regional figures; the page on microclimate shows how.
2. Land shape. Sketch ridges, valleys and the main slopes. A contour map, a laser level, a water level or a simple A-frame shows where the ground is steep and where it flattens. This is the work of the base map.
3. Water. Walk the land in heavy rain. Where does water run, where does it gather, where does it vanish? Mark the places where it could be slowed, spread and sunk, for instance with a swale or a pond.
4. Access. Lay tracks and paths so that they serve the water rather than fight it: along ridges, where little water gathers, or on gentle grades that lead runoff to where it is wanted.
5. Trees. Place shelterbelts, woodland and orchards where they protect, hold slopes and use the water that the levels above have provided.
6. Buildings. Set them where sun, wind, water and paths are already understood.
7. Fences. Draw subdivisions that follow the landscape, not the survey grid.
8. Soil. Build it up where the framework above makes this possible, with cover, mulch, compost and careful grazing.

The scale is an order of decisions, not a timetable. Covering bare soil with mulch is cheap, reversible and useful from the first day. What the scale warns against is an expensive, lasting decision taken before the levels above it are understood.

Later versions

The scale has been widened several times. Dave Jacke and Eric Toensmeier, in Edible Forest Gardens (2005), extended it to eleven items: climate, landform, water, invisible structures such as social and economic factors, access and circulation, vegetation and wildlife, microclimate, buildings and infrastructure, zones of use, soil, and aesthetics and experience. The Australian designer Darren Doherty built his Regrarians Platform on Yeomans' scale and added layers such as economy and energy. Andrew Millison's open textbook at Oregon State University teaches it under the name Keyline Scales of Permanence. Whatever the version, the core is the same: what lasts longest and costs most to change is decided first.

Common mistakes

• Starting with the plants. The plant list is often the first thing people write. On the scale it comes late, after water and access, which decide where plants can thrive at all.
• Roads before water. A track cut across the slope before the flows are known becomes a channel in the first heavy storm.
• Treating soil as fixed. Poor soil is often taken as a final verdict. Yeomans showed that soil changes faster than almost anything else on the list.
• Reading the scale as dogma. It ranks decisions by permanence. It does not forbid small, early steps on the lower levels.

Further in the TerraWiki

• P. A. Yeomans and Keyline design: the origin of the scale and the water system built on it.
• The design process: where the scale sits in the sequence of a permaculture design.
• Swale, retention pond and water retention landscape: techniques for the water level of the scale.
• Zones and sectors: tools for placing elements once the frame stands.
• Spade test and soil analysis: ways into the last level, the soil.

The scale at Sa Medada

Read from the top, the scale describes Sa Medada like this. The climate: a frost-free slope in Jerzu, in Ogliastra on the east side of Sardinia, with mild winters and a dry season from roughly May to September. The land shape and the water: a LiDAR wetness map shows a comparatively dry main area and moister channels along the edges. Swales are planned; none has been built yet. The trees: an old olive grove, and macchia on the steeper slopes. The soil: a laboratory analysis does not yet exist, so no statement is made about its humus or nutrients.

Project Eden begins with pioneer plants, ground cover and holding water.