Science increasingly reveals the degree to which forests shape the atmosphere, soil, rainfall, hydrology and climate. We used to think air, water & soil just happened to be there, and the trees were lucky enough to benefit. Now we know that the oxygen we breathe was produced by plants (and bacteria), nearly all rain in the Amazon basin comes from trees not the ocean, the topsoil essential to our farms was created by forests, and that trees keep many of our rivers flowing while preventing the land from salting.
Unfortunately our European farming systems were set up without this knowledge. Farming now threatens these essential processes and requires much additional resource extraction to compensate for the removed forest ecosystem services of building soil, and capturing and detaining rainfall.
In the Amazon rainforest, slash and burn over large areas turns forest into infertile laterite (rock) within a few years, and it is abandoned. Yet slash and burn has been practiced sustainably by Amazonian tribes for thousands of years. The difference is that small circles within healthy forest are cleared, and allowed to regrow back into forests.
The species in these circles of regrowth are manipulated such that they are all edible. A few months after clearing, crops like beans and sweet potato are harvested. After 2-3 years, people are reaping cassava, papaya and banana. From 5-10 years a number of fruit crops come on line while all of the previously mentioned crops are still produced in the shade or in sun spots below. So canopy, sub canopy, ground covers and vines are all producing. The system continues to develop in size and complexity until the canopy becomes over dominant and the garden phased out. What botanists used to classify “virgin rainforest” can turn out to be an old garden with a 50m tall canopy of brazil nuts and ice cream bean trees.
Many people around the world adapt a scaled down version of an edible rainforest into backyards as small as 20 square metres. So can we. A good way is to plant all the species at once, either on bare soil broadcast with annuals or fully mulched. Either way, you harvest annual vegies soon enough. They shelter the longer lived plants and their wastes add to organic matter.
Locally, perennial groundcovers include sweet potato (the leaves can be stir fried), taro, surinam spinach, okinawa spinach, garlic chives , capsicum. Sub canopy can include cassava, papaya, banana. Lower canopy fits many fruit trees including black sapote, custard apple, grumichama, jaboticaba, lychee, longan. Top canopy can include macadamia, avocado, native peanut, pecan. Sunny edges suit citrus, fig, etc. Pigeon pea is good for nursing the system through its first five years. More species can be found on my website www.ecolivingdesign.com.au/portfolio_page/plants-for-bellingen/.
The maintenance of such a system is low and is easily done with a sharp machete, just chopping weeds or crops that attempt to smother the young fruit trees. As the system matures, it becomes more stable and little chopping is required. It is not only a stable growing system, but a compact one – allowing maximum productivity for a given land size. By using a minimum of land to grow food we release the maximum amount of land back to nature. Which is a good thing – it’s about time we shared the planet.