Friday, April 11, 2014

The Blessing of Constraint: Why Limitations Make Design Easier

It’s so fine yet so terrible to stand in front of a blank canvas
- Paul Cezanne
"Blank canvas" in AP, India
Many people might imagine their dream design scenario to be one in which they are completely free to express their creativity. But like a solution needs a seed crystal for crystals to form, so too does a designer need something with which to get the design started. If we view constraints as seed crystals, the more there are, the faster and easier the design process is likely to be.

Constraints narrow down the possible to the doable. They simplify the process. Limitations are focal points around which you can design. You might consider a site with a lack of an essential resource such as water. Your focus will then be around the capture and conservation of water. As another example, it can make the style of element you add to a design clear. If you face the constraint of freezing temperatures, then you are not going to look at thatched huts as a viable option for housing. In fact, just by having freezing temperatures, your building shape and orientation are largely predetermined for you.

Constraints can also bring you down to Earth, focusing you on what you need rather than what you happen to want at the moment. Financial restrictions, for instance, weed out “what would be great” from what you or your clients actually need.

If you find yourself faced with a big, empty site, look for fixed points you can work around. These serve as a starting point. It’s like a jigsaw puzzle. You find a piece that stands out from the others, and then fit it together with its neighbours bit by bit, forming a foundation.

Friday, April 04, 2014

Empathy in Design


If touchy-feely stuff really turns you off, relax, that's not what I'm going to be talking about here. I'll be talking about a way of viewing systems that opens useful perspectives for assessing and designing them.

The type of empathy we will be looking at is cognitive empathy. Normally, cognitive empathy is assessing the thoughts and feelings of others – getting into their heads, as it were. In applying it to permaculture design, I am using the term cognitive empathy to mean understanding a system's situation and needs.

For example, when I designed my house, there were a lot of appealing design elements and approaches that I really loved. Would I have tried to fit them all in my blueprint, I would have made a disaster. To make the house functional and pleasant to be in, I had to 'get into the head' of the house I was planning. What would the house require given the physical and legal restrictions of location I was to build on? How many of my desires could it accommodate before it started to perform badly? What would the environment throw at it in the future, and how could I design for that?

Use in Design

Empathy is a useful design tool. I'd go so far as to say it is essential for good design. It allows us to design systems that will be more in harmony with natural processes, making them perform better with fewer external inputs.

The water-harvesting designs I have done, for instance, have greatly benefitted by observation of the land in an effort to figure out what the land needs, how it currently behaves, and how water behaves on it. Allowing space for each of these facets allows me to see what I otherwise would have overlooked.


Get a feel for your site. A great way to do this is through passive observation using mindful walking. Mindful walking is a technique of clearing the mind of thought. The approach is quite simple. Walk slowly. For each step forward with your left foot, breathe in and focus on your breath. With each step forward with your right foot, breathe out and focus on your breath. Keep alert with your head up, looking around, but don’t think. Don’t grasp at ideas or think thoughts like "What am I seeing about water availability?" You are walking the land without agenda. Let the observations come to you. Don't force them out. When they do come, note them in your mind, but let them pass. Don't fixate on them.

After you do that, write down any insights you gained about the site. Next, walk the land applying thought and questioning. Actively observe. Take notes. Think. Think like the land. Think like water. Think like the system you are going to put in place. What is it like for you on a regular day? What is it for you on an extreme day? What is going to happen to you over time?

This approach of 'getting into the head' of the system you are trying to design will always help you in designing better systems.

Friday, March 28, 2014

“I love this plan! I'm excited to be a part of it! LET'S DO IT!”

It may have worked for Dr. Venkman and the crew, but loving your plan is a great way to get yourself into a lot of trouble.

The permaculture design process starts with the creation of a clear and concise goal – something that elegantly answers the question "What are we trying to do here?" Your goal is what is distilled from asking why as many times as you can tolerate.

Once you settle on a goal, you enter in on the process of planning. You create a strategy whereby you try to achieve that goal. This is also a stage where you can get into a lot of trouble. One easy way to get into trouble is to fall in love with the plan you've created. You see, the problem is that a plan is just an idea. And let's face it, a lot of ideas are just plain bad. Loving a bad idea makes reality your adversary, and you don't want that. Trust me. Love for a bad plan will have you wasting energy and resources. It will sap your time, money and strength, only to leave you with disappointment.

Don't panic. There is a way to avoid the pitfalls of love. Once you have crafted your goal to the point that it is a concise statement reflecting what you really want, you then set out to make "an imperfect plan." Seriously, call it this, even if only to yourself. We all have imperfect knowledge and imperfect information. What can we hope to create from this? Imperfect plans. Acknowledge that the plan is imperfect. If you admit up front that it is imperfect, you won't be hesitant to make changes in the face of conflicting feedback.

Monday, March 24, 2014

When Swales Can Kill

by Douglas Barnes

Sensationalist title, yes, but unfortunately swales can cause damage, or even loss of life. When designing and building earthworks, "Don't kill people" should be your first rule. I'm going to highlight 3 situations in which these water-harvesting earthworks could be dangerous and perhaps even fatal.

The swale is a water-harvesting ditch on contour.

You've Heard of Quicksand. How About Quick Clay?

When I get a call from a client who is east of me inquiring about earthworks, I immediately head for a soil map. The reason is that much of Eastern Ontario was covered by the Sea of Champlain around 10,000 years ago. Here silt, clay and organic matter were deposited in the sea’s saline environment, leaving a deposit of a particular kind of clay known as Leda clay, quickclay, or Sea of Champlain clay. The salt in the water acted as a flocculating agent (fancy way of saying a substance that allows small particles to form larger clusters). When the sea disappeared, this clay was then exposed to fresh water from rainfall, washing away much of the bonding properties of the salt.

Under pressure, or sometimes when highly saturated with water, Leda clay can liquefy – something which has triggered a number of landslides in Eastern Ontario. If you place a swale somewhere, you are going to make the ground downhill of the swale wetter. This creates conditions that could make the ground unstable, triggering a landslide.

So what do you do in this situation? I don't have any set rules. I look at the need for swales and if other approaches would suffice. I also look at the slope and the likelihood that the land might slide. (Keep in mind that these slides can cover a lot of area and might start a long distance off site.)

In some situations, swales just might help prevent damage. Leda clay contracts a lot when dry, which can lead to foundation damage. If sliding is not a danger, you might help a building keeping the ground hydrated with swales. Personally, I'd look to preserve moisture with mulch and ground cover in those situations, just to be safe.

In short, Leda clay makes me nervous. I've yet to install or recommend any swales in these situations. If you've had any experience dealing with quick clay, I'd love to hear about it in the comments, or via the contact form.

Video by Christian Olsen.

Trouble in Paradise

Swales can trigger landslides in tropical highlands. These hilly areas get tremendous volumes of rainfall. Forcing more water into hillside soils in these regions can trigger a slide, even when they are forested. Consider the following passage from Jared Diamond's Collapse:

Image by Radhakrishnansk
[O]ne European agricultural advisor was horrified to notice that a New Guinean sweet potato garden on a steep slope in a wet area had vertical drainage ditches running straight down the slope. He convinced the villagers to correct their awful mistake, and instead to put in drains running horizontally along contours, according to good European practices. Awed by him, the villages reoriented their drains, with the result that water built up behind the drains, and in the next heavy rains, a landslide carried the entire garden down the slope in the river below.

These are areas of 3 or more metres of rainfall a year. There's no problem with available water in these regions. Don't risks potentially deadly landslides by floating mountainsides with swales.

Swales to Stop a Leaky Basement? No

As mentioned above, swales make the area downhill of the swale wetter. I had someone near the waterfront in Toronto contact me a few years back about doing some work on her property. Her house was at the bottom of a bluff, and she was wondering about swales above her home to keep the water out of her basement in the spring. In this situation, there was the increased risk of sliding, as well as a good guarantee that spring flooding would be made much worse. Sometimes the best advice is not to do anything. I was happy not to ruin her home with swales and I suggested some drainage to carry water away from the uphill side of the home.

Friday, March 21, 2014

Permaculture Home Design, Part 1

The first volume of The Rhizome: Permaculture Journal of Ontario and Québec is out! [76.5 MB PDF]

You can read many fine articles, including a piece recounting part of my journey designing and building a passive solar home.

Wednesday, September 11, 2013

Kingston Introduction to Permaculture Course

Registration for the Kingston course ends Friday! 

This course is also the introductory module for our PDC, should you decide to decide to take the whole course. 

More information is available here.

Monday, July 01, 2013

How to Build Tropical Soils

Building Tropical Soils from Douglas Barnes on Vimeo.

This video looks at building soils in dry and humid tropics, as well as desert regions. The footage is from Andhra Pradesh, India in 2009, and the Loreto Region of Peru in 2013.

For more on the Chaikuni Institute, click here.

Monday, June 17, 2013

Permaculture Earthworks Workshop, July 13th & 14th

Permaculture Earthworks Workshop, July 13, 14, 2013

Thank you to all the students for making this event such a wonderful experience. Invite yourselves back for a visit to see the results.

This class aims to give students a practical understanding of the water-harvesting earthworks techniques used in permaculture. A theoretical section will be taught in which a variety of approaches will be introduced, including dams, swales, ripping, and more. This section will also cover site assessment and design. Students will have practical hands-on time for site measurement, design, layout and implementation. The topics covered in this course will allow students to assess and design their own sites. 

Course books for the theoretical section will be provided to ensure all students have a copy of the material for future reference. The theoretical section will be taught using lectures some topics with student-directed deductive reasoning used wherever possible. 

July 13 
Day one will cover design theory. Students will also learn how to measure the site and map it for design purposes in a hands-on environment. Time will be devoted to design work with student design teams creating their own plans for the workshop's site.

July 14 
Day two will focus on site layout and implementation. Swales will be cut into the site with a dozer. A subsoiler will also be used for patterned ripping of the soil. As part of the hands-on component, the swales will be groomed and level-sill spillways cut into the swales. The use of various levels will also be demonstrated, with students having an opportunity to use them in practice. 

Equipment needed 
Students should bring a notebook, pens, pencils, a shovel (if possible), work gloves, boots, and rain gear. Sunscreen is also recommended as we will spend prolonged periods outdoors. Meals and accommodations will not be provided during the course. Contact Douglas for a list of area accommodations.

Please note that to provide the best learning environment, we are limiting ticket sales to 20 tickets.

Saturday, February 02, 2013

2013 Guelph Organic Conference

The following is a write-up of my February 1 presentation at the Guelph Organic Conference. Many thanks to the event organizers and staff, my fellow panellists, and most importantly to the wonderful, engaging audience.

Permaculture Earthworks

by Douglas Barnes

We are fortunate to live in a climate that is relatively abundant in water. The disastrous drought of 2012, however, shows us that we can no longer afford to take water for granted. Globally, nearly half of all land is arid, with a further 25% threatened with desertification. That's the bad news.

I'm here to tell you the good news. I’m here to tell you about how, with a fraction of the time and energy we have spent degrading our environment, we can foster life and increase biodiversity. And we can do it profitably.

Let me jump right into the "how." The "how" is based on a few design strategies. One of those strategies is to hold onto the resources we have on site as long possible. In the case of water, we hold onto it in two ways. One is to put it through as many duties as possible before it is lost to us. The approach we are focusing on today, however, is to capture the water arriving on site, and take it over the longest, and slowest path practical.

Putting this approach into practice means starting at the highest elevation on a site and working downhill with the techniques I am about to highlight.

To hold water at the top of a site, we typically forest hilltops and ridges, along with steep slopes. Forests are very effective at capturing water with minimal runoff. They also have the added benefits of preventing erosion, and adding fertility to the top of a site where it can naturally flow downward. This is a strategy hit on by the Japanese in a traditional mountain region farming system they call Satoyama. Admittedly, this is not a form of earthworks, but it is so integral to water harvesting design that I would be remiss not to mention it.

Water harvesting earthworks have the goal of intercepting runoff water, and storing it. The simplest of the interception techniques involves patterned ripping of the soil with a subsoil plow, given the right soil conditions. With the plow, we cut narrow furrows into the ground just slightly off contour to capture runoff and gently direct it from wetter areas to drier ones. Originating in Australia, this technique has proven very effective there.

This type of interception technique is also really a storage technique as well. The ground is a fantastic place to store water. There it is largely free from evaporation while being available to plant and soil life.

Another common interception technique is the swale, which is a water harvesting ditch dug level on contour. It stops water flowing downhill, allowing it to sink into the ground.

This is a good point to address an argument that too often comes up around water harvesting. Sometimes you will hear a claim from downhill people that you are "stealing their water." Nothing could be further from the truth. They might see a temporary reduction in runoff onto their land as you hold onto more of your water, but, as you recharge the water table, the medium and long term effect will be to increase the local ground water. In many cases, ephemeral streams will start to have a more regular or even constant flow.

Both of these interception and infiltration techniques are inexpensive and cost effective to install.

Swales are also used in conjunction with earthen dams and ponds. The dams we are talking about are small reservoirs sealed with clay, not concrete structures. Both ponds and dams provide water for irrigation. They can also be put to productive use through aquaculture. While our climate does not support a very large variety of productive aquatic crops, warmer climates can produce prodigious quantities of edible and palatable plants. And even in our climate, water has a better feed conversion rate than terrestrial livestock. For instance, it generally takes 870 grams of feed to produce 100 grams of beef, or 190 g of feed to produce 100 g of chicken. The feed conversion rate for fish, however, is typically 120 g of feed to 100 g of fish.

Aquatic systems are also excellent producers of soil. Their periodic need for dredging yields a very valuable product that adds to site fertility.

In semi-arid and arid conditions, we sometimes employ a land imprinter - essentially a large, patterned drum which can break through desert hard pan and leave divots in the earth. Here debris, including seeds, will collect and moisture will concentrate during rains. This simple approach has proven effective in re-establishing grasslands.

Dug pits can work similarly to establish drought-hardy trees in semi arid conditions.

This has been a very rapid summary to give you a taste of some of the techniques we use. I'd like to leave you with a brief case study of the most dramatic work I have been involved in.

In 2009, I received an invitation to carry out a joint project with a local NGOin Andhra Pradesh, India. This region had traditionally had a dry tropical climate. In recent decades, however, it has grown increasingly arid at an accelerating pace.

When I finally arrived, I found the situation on the ground to be quite bleak. The vegetation is starting to give way to cacti and other desert xerophytes. The local village I worked in now has to draw water from a well over 1000 feet deep, the water from which is tainted with excessive amounts of naturally occurring fluoride.

Before leaving, I'd had it in mind to employ a number of techniques, including ripping the ground with a subsoiler, and building a dam. The soil conditions only lent themselves to swales, however.

I was given carte blanche over 7acres of arid hillside that a local mango farmer considered a write-off for everything except a seasonal crop of pigeon peas.

After crunching some formulas, we laid out contour lines on three levels, then excavated over 400 metres of swales, capable of holding over 1 million litres of water.  Our host farmer was initially dismayed to see us chewing his land up, but started to get the gist of what we were doing. The night before we were to complete the project, a pre-monsoon storm hit, so when the rains hit, he took off on his motorbike, and headed to the site. He was delighted to see that all the water that would have washed down the hillside, and eventually out to sea, was now stored in the ground.

Before I left, I made what I thought was a bold prediction. I said that within 3 years time, there would be springs appearing at the bottom of the hill during the monsoon season. It turns out that my predictions were very conservative.

Six months after I left, I received a photo update of the site. In it, I saw that they had established mango seedlings, and they had managed to do it without drip irrigation - something very unusual even on flat sites in the area.

Tamarind trees on the opposite side of the valley had a very anemic crop, whereas a tamarind tree adjacent to the swales produced an unusually bountiful crop.

I'd made my bold predictions of springs appearing within 3 years. At the bottom of the site there had been a well with water 3 metres down while I was there. Now six months later, the well was full. Water is no longer an issue on the site. And what had been a meager pigeon pea field is now a lucrative mango polyculture.

The results were beyond my most optimistic expectations, and the cost of the immediate project was just $650 Canadian. This is really a prime example of how the cost, effort and time it takes to repair a site is far less than that required to destroy it in the first place. As soon as we pattern our actions in harmony with nature, the payoff is immediate.

These techniques have proven effective everywhere from arid desert to tropical rainforest. They help to rejuvenate drylands, and buffer against drought. We can expect increasingly erratic weather in our future, including severe drought. These water harvesting approaches can help us through the rough times to come, and they can replenish our water tables during the good years.

Friday, October 19, 2012

Species of the Month: Tilia americana

Thanks to a student of mine, Tom Marcantonio, I gained an appreciation of this common temperate North American tree. Tom had learned of the use of its inner bark for cordage, and was using stakes, and cordage made from the tree to support his plants.

Tilia americana, also known as Basswood, and American Linden, is hardy in USDA zones 3 to 8, making it a common feature on the landscape. It does well on deep, well-drained soils, but it can handle dry or heavy soils. Left alone, it could grow to 21 meters (70 feet).

Its a useful winter browse for deer, and its buds are food for birds. The summer fruits are eaten by birds, squirrels, and mice. Older trees tend to rot out in the center, leaving habitat for animals. Its nectar makes it a good bee fodder. However, it does have the tendency to attract pests; among these are borers, aphids, leafminers, scale, and Japanese beetles. As we say, however, the problem is the solution. This tendency might make it a useful tool in a push-pull integrated pest management regime. If anyone has tried this, please let us know how it went.

Image by Tie Guy II
The soft wood does not splinter easily, making it a good wood for carving. Its ability to coppice makes it all the more appealing. To make cord, soak branches, then peel off the bark. The inner bark is the part then made into cord.

The sap has traditionally been boiled to make syrup, or taken as a drink. Young leaves can be cooked and eaten as well.  The nuts and flowers can be ground into a paste that is said to have a chocolate taste. I’d love to test the truth of this claim. The flowers can be put in salads, or brewed into a tea. I have seen one recommendation cautioning moderation in drinking the flower tea as it could cause heart damage. I think this warning stems from the β-Sitosterol it contains. For this reason, it is probably best for pregnant women to avoid altogether. The flowers do have a whole host of interesting chemicals in them, including but not limited to bioquercitrin, which helps regulates cell growth. Recent research suggests that T. americana can be used as an anti-anxiety treatment.

There are a few places I could use this tree on my site as part of a shelter belt. Though I have seen no mention of its use as a fodder tree, I would imagine it could be used as such. I suspect it would work well in a silvopasture setup.  Its many fine properties make it an appealing candidate that I am sure to utilize.

Sunday, October 07, 2012

Site Mapping for Permaculture Design – November 2012

Date: Saturday, November 3, from 1-3:30pm
Rain date:  Sunday, Nov. 4th, from 1-3:30pm
Location: meet at Just Food Ottawa’s office,
2389 Pepin Court, Ottawa, ON, (in Blackburn Hamlet)
Suggested donation: $10-30 (no-one turned away for lack of funds).  Any extra money raised will go towards Permaculture Ottawa’s Community Urban Food Forest project.
Transportation: OC Transpo bus #94 Millenium, some ride-sharing will be available.

Join us for a hands-on workshop that will introduce you to the basic site mapping skills used in permaculture design. Participants will learn how to measure and map a site’s features, including elevation.  The workshop will be led by Douglas Barnes, an experienced permaculturist who is the president of EcoEdge Design Ltd. Douglas studied with permaculture founder Bill Mollison, and has worked on projects in Canada, Japan, India, and Australia.
This workshop will take place outdoors, so participants should take the weather into account and dress appropriately. Participants please bring your own paper, pens or pencils- and if you have one, a 100′ tape measure will come in handy!  The workshop organizers will provide a set of workshop notes for the students, a surveyor’s level, A-frame level, bunyip level, farmer’s level, GPS, twine, stakes, a measuring wheel, and two 100′ tape measures.

* Limited space available- to reserve a spot email
Sarah Lévesque-Walker at
and write “Mapping workshop” in the subject heading.

Sunday, September 30, 2012

Patterns in Nature: Waves and Spirals

Patterns In Nature: Waves and Spirals

by Douglas Barnes

The information here will be instructive regarding the functioning of the universe (of which the designer should have at least a rough grasp). It is useful when considering the temporal aspects of growth (i.e. how things grow over time), but is only marginally useful as a physical design template. It does, however, happen to be really fascinating.

In Bill Mollison’s Permaculture: A Designers’ Manual there is a passing reference to “Winfree’s ‘doped’ chemicals" that long ago caught my eye. The chemicals Arthur Winfree was working on were, in fact, the Belousov Zhabotinsky Reaction, which is what is known as a reaction-diffusion system. As we'll see, such systems govern many of the biological and physical systems we see in nature.

Before we get too far ahead of ourselves, let’s start with Boris Belousov. Belousov was looking for clues on the glycolysis process (and happened to be on the right track, too). He found a reaction that would react, reverse, and repeat the process with a regular period.

In trying to get his research published, he was given the brush off by the establishment because, to the world of chemistry at that time, what he was claiming sounded akin to striking a match, then having the process reverse, then reignite, then reverse, and so on. All known reactions at the time settled linearly into an equilibrium state.

Later, Anatoly Zhabotinsky took a look at Belousov’s work, and expanded on it. The reaction the two scientists pioneered became known as the Belousov-Zhabotinsky reaction. The BZ Reaction is a catalytic reaction in which the catalyst forms out of the reactions own reactants. This autocatalysis burns out and meets with a different reaction that forms products needed to restart the autocatalysis once again.

In the reaction, travelling circular waves emerge and propagate outward. Should those waves happen to meet with an obstruction in the medium, they form spiral waves - something we will come back to several times in our explorations here. Describing it only goes so far. It’s better to see it for yourself.

Reaction-Diffusion in Nature

Reaction-diffusion systems also occur in nature – a lot. In a biological system, cells will start in a state susceptible to excitation. They become excited from the stimulus of neighbours, passing on the excited state. They then go into a period of recovery. This is embedded in the mathematical template governing the chemical automation that runs your body, other life forms, species interaction, and possibly galaxies, too.

Your heart operates this way, for instance. A wave propagates across your heart, giving the cells an instruction to beat. If it meet an obstruction – a damaged area of the heart – a spiral wave can form and propagate, as in the BZ reaction. This is what happens in ventricular fibrillation when one has a heart attack.


This same reaction-diffusion dynamic (excitation, spread, recovery) occurs in interacting species populations, as well. For instance, you see the waves temporally in pest populations in your garden. The pests appear, providing an untapped food source. Predator populations then respond with increased localized populations, reducing the initial wave of pests. The loss of food leads to a decline in predator population, allowing a recovery of the pest/prey population.

Similarly, you might also notice this model is at least prima fascia applicable to memetic social systems like propaganda, for example. True or false horror stories about the official enemy emerge, followed by outrage in the population with potentially deadly results, followed by a return to relative sanity. Repeat as necessary, nationality irrelevant. You might also imagine similar patterns emerging in economics, fashion, and so on.

Enter Chemotaxis

Let’s consider a bacterial population. One cell emits a chemoattractant that diffuses out into the medium it is in. Detecting this signal, neighbours are drawn in. The neighbours congregate where there is the greatest concentration of chemoattractant, resulting often in either circular waves, or spiral ones.

Spiral wave propagation looking in Dictyostelium discoideum
looking very much like the BZ reaction. From

I've noticed the same pattern often emerges in mycelial propagation. Enter Paul Stamets who has noted the appearance of these patterns in his book Mycelium Running.

Nature tends to build on successes. The mycelial archetype can be seen throughout the universe: in the patterns of hurricanes, dark matter.... The similarity in form to mycelium may not be merely a coincidence. - Paul Stamets, Mycelium Running

Spiralling Psilocybe and Armillaria, respectively.
From Mycelium Running by Paul Stamets

I would say indeed it may not be. I would argue that these forms are mathematically predestined. (This is not to suggest, however, that hurricanes are the product of reaction-diffusion systems. They emerge out of fluid dynamics.)

Galaxies? Really? Come off it!

I had always only ever thought of galaxies coming about as a result of gravitational interactions. My education in physics being limited to undergrad studies, I did not encounter much in the way of astrophysics, unfortunately. As it turns out, the way I had envisioned galaxy formation to occur would, in fact, result in a galaxy that would quickly wind so tightly was to appear to be just a nondescript disc.


This problem of formation was mostly solved when Chia-Chiao Lin and Frank Shu proposed the Density Wave Theory, in which the density of the spiral arms of the galaxy prevents the galaxy from winding up into a disc.


It is a great theory, elegant, simple, plausible, and with backing evidence. But it doesn't quite explain every type of spiral galaxy. Theoretical physicist Lee Smolin had a look at the problem of galaxies where the density wave doesn't hold, and proposed a hypothesis whereby the galaxy was actually one great reaction-diffusion system. In his model, shockwaves from star formation and supernovas drive one reaction, and ultraviolet radiation from giant stars serves to inhibit it. The hypothesis isn't perfect but just might explain some aspects of galaxy formation.

Now Available in 3D!

The BZ reaction shows a two dimensional expression of the propagation of travelling waves, or spirals, as the case may be. Taken in three dimensions, the travelling waves form expanding toroids, or, in the case of spirals, scroll rings. This form is reminiscent of the much talked about but perhaps sometimes misunderstood “core model” in permaculture (more on this in a future article).

Scroll ring. From riowight.

Take the example of a jet of fluid flowing forward into a medium. The leading edge thrusts forward, and friction at the sides slow it down, creating a mushroom shape. These edges often form spirals as the following image of a portion of a von Karman vortex street shows. Keep in mind, however, that this is a characteristic of fluid dynamics, and not the product of a reaction-diffusion system. I am including it for illustration purposes only. Remember, though, that the appearance of spirals in a reaction-diffusion system is a result of fluid dynamics. Hence the relevance.

Portion of a von Karman vortex street. From

 So there you have it, spirals from wave propagation. Is there some great mystical universal something going on? I believe these patterns emerge because they must. They are the mathematically prescribed result of chemical interaction in space and time. Galaxies do not form giant portraits of Homer Simpson because that is not a mathematically possible outcome. Bacteria propagating in a uniform petri dish do not form interlaced nonagons because that is not a possible outcome. What you see is what you can get.