Cycle thinking in permaculture

What cycle thinking means

An oak leaf that falls in autumn is not lost. Over the next few years woodlice, springtails, fungi and bacteria take it apart, and what it held returns to the roots of the same tree or its neighbours. Dung feeds beetles, dead wood feeds fungi. In an intact ecosystem the word waste has no real meaning: what one organism leaves behind is food for another, and the same atoms of nitrogen, phosphorus and carbon pass through countless lives.

Modern economies mostly run in a straight line: take, use once, throw away. Food travels to the cities, and its remains leave through the bin and the sewer. At the start of the line something runs short, at the end something piles up where it does harm. Much of what we call pollution is a resource in the wrong place.

Cycle thinking bends this line back into a loop. It asks of every material on a piece of land where it comes from, where it goes next and who could use it on the way. No real system is completely closed: harvests leave, rain washes some nutrients away. The goal is shorter, tighter loops that lose little and need little from outside.

How permaculture understands it

Cycle thinking runs through permaculture from the beginning. In Permaculture: A Designers' Manual (1988), Bill Mollison described farms and gardens as webs in which the output of one element becomes the input of another. Two rules from his teaching are part of many design courses to this day. Each element should perform several functions, and each important function should be supported by several elements. A pond can store water, cool the air and feed fish; the water supply of a garden, in turn, should not hang on a single tank. Mollison is also credited with a bolder thought: that the yield of a well-designed system has no fixed ceiling, because the number of uses a resource can be put to is limited above all by the information and imagination of the designer.

David Holmgren condensed permaculture practice into twelve principles in Permaculture: Principles and Pathways Beyond Sustainability (2002). Five of them read almost like a description of cycle thinking.

Catch and store energy. Sunlight, rain and the growth of a season are abundant for a while and then gone; Holmgren pairs the principle with the advice to make hay while the sun shines. Water in the soil, humus, seed and wood carry a time of plenty into leaner months.

Use and value renewable resources and services. Nitrogen-fixing plants feed the soil, earthworms loosen it, hens scratch and manure. Using such services means less fuel and fewer bought inputs.

Produce no waste. The icon of this principle is the earthworm, one of the most effective recyclers of organic matter: it lives on plant litter and turns it into humus that serves the soil, its microbes and the plants. Holmgren contrasts this with cheap mass-produced goods that are not made to last and with plastic packaging, made from oil and used only briefly. Waste, in this reading, is a sign of an unfinished design.

Integrate rather than segregate. Cycles form only where elements are close and connected: a henhouse at the edge of the vegetable garden, a compost heap between kitchen and beds.

Apply self-regulation and accept feedback. Pale leaves, a crust on bare soil or a gully after heavy rain show where a loop is leaking. Permaculture asks the designer to read such signals and to build systems that largely correct themselves.

Energy drives the cycles

As the page on energy flow explains, energy does not circle. Water, nutrients, carbon and material can pass through the same field again and again, but the energy of sunlight is used up as it works and finally leaves as heat. Mollison's teaching speaks of energy cycling, and what it means is a practical aim rather than a law of physics: to pass stored energy from one use to the next on site for as long as possible before it is gone.

The sun also drives evaporation and rain, but the living cycles of the land keep turning only while plants capture fresh sunlight. Permaculture therefore asks two things of every place: how much of the incoming light falls on living leaves rather than bare ground, and how long the captured energy stays in the system as sugar, wood, humus and soil life before it escapes as warmth. Layered plantings such as a food forest, soil that is never bare and prunings that stay on the land are the answers.

From principle to design

In practice, cycle thinking means placing things so that the waste of one element becomes the resource of the next.

Kitchen scraps go into compost, and the compost goes onto the bed that supplies the kitchen. Rain from a roof is led into a cistern and from there into the garden in the dry months. Prunings and cut green plants are laid down as mulch, feed worms and fungi and come back as crumbly soil. Animals graze, leave their dung on the pasture, and the pasture grows again on what they leave.

Distance matters. Zone planning, as Mollison taught it, puts whatever needs daily attention close to the house and whatever needs little care further away. A compost heap at the far end of the land is soon neglected, and the scraps end up in the bin after all.

Diversity matters too. A single crop draws on the same nutrients and leaves residues that few other elements can use. Mixed plantings, plant guilds and the stages of ecological succession create many small exchanges. Deep roots take up minerals from the subsoil that return to the surface with their leaves, and nitrogen fixers feed their neighbours when they shed leaves or are cut. Syntropic agriculture goes a step further and prunes hard and often, so that plant matter keeps flowing back to the soil.

The six cycles in the TerraWiki

The section Closing the cycles looks at six loops one at a time: how each runs in nature, where ordinary land use breaks it, which techniques close it again and how it looks at Sa Medada.

• The water cycle follows the rain from leaf to soil to vapour and shows why holding water in the slope comes before any tank.
• The nutrient cycle traces nitrogen, phosphorus and other nutrients from air and rock through plants and soil life back to the roots.
• Carbon and humus describes how carbon from the air reaches the soil, how long it stays there and why that store can be lost again.
• Energy flow explains in detail why sunlight drives all the other cycles and where land use squanders it.
• Biomass and material follows leaves, wood and prunings from growth to humus and asks why so much of it is burned or carted away.
• The seed cycle shows how plants sow themselves and adapt over generations, and how gardeners can take part.

How Terra Humana approaches it at Sa Medada

Sa Medada is a slope in Jerzu, in Ogliastra on the east side of Sardinia, with mild winters and a dry season that lasts roughly from May to September. An old olive grove covers part of the land, macchia grows on the steeper slopes, and the LiDAR wetness map shows a comparatively dry main area with moister channels along the edges. On land like this, water sets the pace for every other loop.

Project Eden therefore begins with pioneer plants, ground cover and holding water. Swales are planned; none has been built yet. Several nitrogen fixers are already in the ground, among them Tephrosia, the coral tree, Inga edulis and Leucaena. Their prunings are meant to go back onto the soil as mulch where they grow, so that what grows on the slope stays on the slope; how much this contributes has not been measured. A laboratory analysis of the soil does not exist yet, and so we make no statements about its humus or nutrients.

Terra Humana understands its work as renaturation and rehumanization: bringing life back to damaged land and finding a place for people inside these cycles rather than outside them. Part of this is our view of so-called invasive species. Fast-growing newcomers are, in our understanding, nature's own strategy for repairing disturbed ground, and they hold the greatest potential for rapid renaturation when they are guided and gradually replaced. Species on the EU list of invasive alien species of Union concern, however, Terra Humana never uses.