Imagine the Valley of Mexico, home of the Aztec people and present day Mexico City, in 1519, when the Spanish first arrived. What comes to mind first? Human Sacrifice? Well, there was some of that going on… but let’s not go there. The Aztec empire at that time was supporting a population of 5-6 million people. That’s a lot of people to feed. Now, can you imagine the agriculture systems that were commonly used to feed all of these people?
It turns out they were using a system of combined Aquaculture and Agriculture called chinampas. Also referred to as “Floating Gardens”, chinampas are typically rectangular gardens protruding into or floating within lakes or ponds. When the Spanish arrived in 1519, what they found was a vast network of chinampas in the shallow lake beds of the Mexico Valley, built from water hyacinth reeds, and soil. These vast systems of floating gardens protruding out from the lake shore, were self-watering, self-fertilizing, navigated easily by boats, and highly productive. These sophisticated traditional systems demonstrate a perfect example of the kind of multi-functioning, self-supporting, and life-regenerating systems we seek to create using Permaculture Design.
I first learned of chinampas in an Ethnobotany class, when I was studying Botany at the University of Texas at Austin, and was very intrigued at the concept of floating gardens. I later encountered an example of this technique while traveling in Bolivia in 2008, where the native “Uru” people of Lake Titicaca build entire floating islands from the reed plants that grow at the edges of the lake. They keep stacking these floating reeds until it becomes a large interwoven floating mass. Each year they continue stacking more reeds on top, as the bottom of the island slowly decomposes into the lake. They were growing crops on these floating islands, building houses, boats, and many other necessities out of the reeds, and even eating the reeds. I then forgot about the idea of chinampas until the technique came up in my first Permaculture Design Course in 2011. I was so pleasantly surprised to reencounter the technique, as if an old friend came to visit after a long separation. I told myself, “Someday I’m going to design and build a chinampa system”.
Now, my opportunity has finally come. I’m here in East Bali, managing Tirta Gangga Organic Farm, which is an entirely spring-water irrigated system of terraces supporting various crops of organic vegetables, grains, fruits and herbs. The farm is directly located beside the abundantly spring fed, Tirta Gangga Water Palace, built for the King of Karangasem, Bali in 1948. As the farm is also abundantly fed with fresh flowing spring water, and any of the terraces can be selected to receive water at any time, I thought “This site is just begging for chinampas”. Now we are in the process of installing some small chinampas to start with. You can learn about these systems as well as the full spectrum of methods and techniques in our upcoming Permaculture Design Certification Course at Tirta Gangga Organic Farm in Bali, August 16-31.
It turns out, floating garden systems are not novel to South East Asia and may even have roots here dating back to far before the Aztec Empire in Mexico. Chinampas are also found to this day in Asia (though they are not called chinampas of course), such as in Vietnam, and the famous floating gardens of lake Inle in Myanmar. As we know, the indigenous people of the Americas originally came from Asia. The most commonly accepted theory is that most of these peoples came by foot over the Barring Strait, but there is immense evidence that this migration was also by Sea navigation. The Maori people of New Zealand for example, have extensive records of Navigational routes to various other islands in the pacific, and as far reaching as Peru. The Polynesians had, and still have, sophisticated knowledge of navigation, which brought them to inhabit the Islands of Hawaii, and perhaps even parts of Central America. It is possible that this combined agriculture aquaculture system was one of the techniques brought over in that migration. But given the immense productivity of chinampa systms, it would be no surprise if it was discovered independently across cultures.
So what makes this system so productive?
Well one way of looking at this is that the combination of Agriculture and Aquaculture, as in an aquaponics system, can create a more or less “closed loop system” where nutrients are cycling within all life in the system. The plants create food for the fish, the fish create fertilizer for the plants, and the abundant sunlight and carbon dioxide create more plants to feed the fish.
There’s another way to look at it though. Permaculture design principle number ten tells us to “Use edge and value the marginal” in the design process. The edges are always where you find the most biodiversity and productivity in Nature, such as in an estuary, where the river meets the ocean, or at the edge of a forest and prairie. Where edge is maximized, there is more functional bio-diversity, and therefore more stability, resilience, and productivity. Chinampa systems, if designed well, can have an immense amount of horizontal and vertical edge. “You may have canopy trees, understory trees and shrubs, land crops, edge crops, emergent crops, trellis crops, fish, crayfish, water fowl, chickens on the land base, and floating water plants for fertility and mulch production… It’s due to all of this vertical and horizontal edge [in a chinampa system] that made it the most productive system ever documented per square meter.” –Geoff Lawton (from a PDC course he co-taught with Bill Mollison). There is an immense amount of possibilities for cultivating these systems. Like Geoff mentions, you may have trellises hooping over the waterways with fruits hanging down which can be harvested by boat. You may even design in a way of easily draining the waterways to harvest fish/crayfish, and flooding the land base to bring nutrient rich water to the plants. The possibilities are nearly endless.
How to create a chinampa system?
There are many appropriate ways to go about it, depending on your starting conditions, but I’ll share the process by which we’ve been creating them here in Bali. Our first installation was on a former rice terrace, which had water flowing through it and raised keyhole beds coming out of the water filled with water loving plants such as mint and Ipomoea aquatica (water spinach). The soil in these beds was very dense, anaerobic, and very rich in nutrients from all the algae content. My basic strategy was to dig out half of these bed areas into ponds, and build up the beds left behind with the soil removed for the ponds, while layering in straw and sand to lessen the density and create more aerobic soil conditions. The entire edge of the terrace has a strip of free flowing water going around the beds and the water finally spills out down into the next chinampa system below. The ponds I chose to dig at least one meter deep so that the temperature of the pond would be moderated by it’s thermal mass. In other words, if the pond is deeper, the water is not so easily warmed by the sun or chilled in cool climates, which makes for a more stable aquatic ecology.
For those with large ponds, or lake-shore property, you could try the age old method of piling floating reeds from the edge to create a truly “floating” garden, with soil on top. This of course requires the presence of reeds such as water hyacinthI have not tried this kind of installation before, but my guess is that you would have to have a predominance of reeds as a base, and just enough soil on top, but not too much, so the reeds can support the weight of the soil. You could try weaving in plastic bottles filled with air (a great re-use of a common waste product), tying them to bundles of reeds. I bet bundles of straw could even be used if you had a way of tying them all together with plenty of plastic air bottles attached (If anyone has success with this, please contact me: email@example.com) Organic Matter such as reeds or straw will act like a wick to bring water up to the soil.