Mexico City was founded by the Aztecs in 1325 AD and was built on a vast lake and a series of wetlands.
This ancient culture created an incredibly productive farming system using the rich silt at the bottom of the lake to create constructed farmlands or “chinampas”, growing food and supporting a population of about 300,000 people. Organic waste, including human and animal manures, was continually recycled back into the soil, creating a fertile growing structure with an organic matter content of about 11%.
Chinampas are sometimes referred to as ‘floating gardens’ although they are actually anchored to the ground and filled with layers of plant matter, water weeds, and other organic waste which continuously breaks down and is continuously added to. Trees planted around the edges of the islands stabilise the soil and prevent it from running off.
Before the Spanish conquered the region in the 1500s the chinampas covered an area of approximately 235,000 acres however the Spanish began draining and filling in the canals and built what is now known as Mexico City.
The area of Xochimilco, located about 23 kilometres from the centre of Mexico City, is the only area that still has constructed chinampas in use with about 80 families still farming and continuing to use the successful ancient cultivation techniques including continuously recycling nutrients, not using chemical pesticides or fertilisers and maintaining the structure of the chinampas as they have been since ancient times.
For many decades the area has been degraded due to the waste water, sewage and chemical runoff from Mexico City as well as continuing encroachment into the land from property development. However, in recent years the value of this precious ecosystem to the city has started to become apparent and there is more and more pressure to protect and conserve it. It has been declared a UNESCO World Heritage Site for its cultural and environmental significance, eco-tourism and the demand for locally and ethically sourced produce from high-end chefs which brings hope to this important area.
The federal government has started an ecological rescue project to improve the health of the ecosystem and wildlife - in particular by providing a breeding area for the endangered axolotl, which depends on these lakes for survival. Their survival has been threatened not only by the draining of the lakes and the water pollution but also by the introduced tilapia which eats them (ironically, the tilapia was introduced to eat the goldfish that had been introduced and were out of control - thoughts of the introduction of the cane toad come to mind).
Most tourists from Mexico City and beyond only know Xochilmilco as a place to go for festivities on the ‘trajineras’ or colourful party boats, enjoying floating down the river, drinking, eating and singing along with the mariachi groups on passing boats. While this brings income to the area for the musicians, boat owners, local caterers and so on, it also leads to litter and does not necessarily support the environmental activities in the area.
Ownership of the chinampas is passed down through generations of families and some have abandoned them, some have converted them to sports playing fields and about 80 families are carrying on the traditional farming practises which take care of the water, produce organic food and process organic waste. All organic waste produced on the farms is returned to the soil and food waste produced locally as well as from within Mexico City itself is converted to compost to regenerate the soils of the chinampas.
Farmers using traditional methods understand that keeping these practices alive is not merely to act as living museums but to show how these methods are needed more than ever as cities face the impacts of climate change, food insecurity, soil depletion, and numerous other issues. The grasses on the edges of the beds and the high organic matter and biological activity in the soil act as a bio-filter and assist with cleaning and improving the water quality.
One ingenious method farmers use for germinating seeds is to use the silky mud from the canals, pour it flat and let the top layer dry out. This becomes a seedling nursery bed which is then sliced into suitably sized blocks where seeds are planted into. Once the seed germinates the block it is growing in is pulled out and planted directly.
This method does away with the need for plastic pots, creates minimal root disturbance with transplanting and gives the plant a highly nutritious growth block with excellent water-holding capacity for its start in life.
The chinampas of Xochimilco illustrated to me that even so close to such a massive city it is possible to bring together modernity with ancient wisdom in order to protect and preserve significant environmental assets, not out of a glib nod to the quaintness of the past, but as a crucial measure to minimise the effects of climate change and environmental damage that has occurred over the last few hundred years.
The culture and land of the chinampas are still under threat but I hope the Mexican government takes measures to extend the protection of the area and to support the efforts farmers and groups within the city are taking to use ancient cultural methods to convert food and garden waste into rich soil that not only grows food and fosters community but also cleans waterways and supports threatened wildlife. Similar opportunities exist within and around Australian cities as we manage our own limited resources and deal with the damage that has been inflicted on the land over the last 200 hundred years
Visiting Mexico City was part of my research for a Churchill Fellowship exploring education methods and partnership models to support community composting. For more details visit my Churchill Fellows Portal where the full report can also be downloaded.