Subsistence agriculture is where farmers primarily grow food for themselves and their families. It has a long history with many traditions and clever methods that minimize losses and make the most out of the soil.
A desire to grow our own food is strong.
After all more than 3 billion people [45% of the global population] make their living from agriculture.
For example, in Uganda more than 30 million people [86% of the population] will typically grow most of their vegetables in a small kitchen garden. Yams, sweet potatoes, corn and green veggies are grown and harvested in rotation for all year round supply that is supplemented by ‘matoke’ a starch made from green bananas harvested from groves nearby.
It is possible in the warm, wet climate to grow enough food in a very small area. Over time farmers have learnt the best combination and sequence of crops to maintain yields and reduce the risk of pests and disease even when they have little or no access to fertilizers and pesticides — and they get help from the deep laterite soils that retain sufficient nutrients to sustain many rotations.
The techniques and skills required for successful subsistence agriculture are about maintaining soil quality and conserving nutrients by using mulch, manure and compost — many are adapted for urban farming.
But unless there is a nutrient subsidy from beyond the plot, in time nutrients are used up and fertility begins to decline. Alternative crops may run another season or two but eventually plots are abandoned and the farmer forced to move to a fresh location.
Variations on this practice of shifting agriculture occur throughout Africa, Asia and South America.
Once a plot is abandoned secondary forest vegetation returns and slowly replenishes the soil. Given enough time the plot can be cleared again for a new sequence of crops.
The modern challenge is to find the space to grow food like this.
130 years ago in the early 1860’s the explorer John Hanning Speke — now remembered with a monument in Kensington Gardens, London — walked his way across East Africa including parts of what is now Uganda.
There were few people back then, perhaps 2 million at most. At independence in 1962 there were 7 million Ugandans and just 50 years later in 2012 there were 36.5 million.
Uganda is a sizable place with around 197,000 km2 of land and so there was no surprise that Speke would have seen unbroken forests and grasslands with more wildlife than people. Subsistence agriculture could move around easily with nearly 1,000 ha of land per person.
By 2012 though there was the equivalent of just 54 ha per person.
This is still more than enough for successful subsistence agriculture and the population continues to grow. It should be possible to shift the average sized plots of 0.2ha for quite some time still.
Except that not all the land is available — space is needed for cities, transport, utilities, commerce, tourism and industrial agriculture [not to mention the African wildlife]. And where land is steep, waterlogged or infertile it is not suitable for subsistence agriculture.
There is actually a lot of pressure on that 54ha per person.
Across Asia subsistence farming often stays put — plots are cultivated for generations using traditional methods of crop rotation and low cost inputs.
The reason this works is that the systems of cultivation evolved to replace the nutrients that leave the fields in the crop with inputs from elsewhere. Manure, green compost, mulch, and in some cases inorganic fertilizers replace the nutrients to maintain crop yields.
And often yield are quite low, below what the soil might be capable of delivering. This seems odd to western agronomists with a commercial mindset, yet running the system below its full potential preserves it — rather like driving a car without sending the rev counter into the red.
This combination of subsidy and restraint built into a long and respected tradition of cultivation allows some subsistence farmers to be sedentary for a long time.
These rice paddys in West Papua, Indonesia form part of system of arable fields and oil palm plantations that allow farmers to subsist in the same area without reverting to shifting agricutlure
It should be a staggering statistic that nearly half the people in the world grow almost all of their own food — even if it may come as a shock to those of us used to getting our food from the shopping mall.
It should also be staggering [and even a little disconcerting] that this system still works given world population growth.
It should be a huge worry that in many places subsistence agriculture, especially shifting cultivation systems, is at risk of reaching its limit.
The reality is that there is no longer enough land to sustain shifting agriculture and before the activity finally stops much of the worlds native forest will have been cleared.
This is not the fault of the farmer who is just doing what anyone would do to feed his [or her] family. Nor is it the fault of those fortunate ones who can shop at the supermarket. It is what it is.
There is, however, a choice.
We can choose to see this as one of the global environmental issues that has a solution or we could ignore it.
Cultivation in the highlands of Papua New Guinea has gone on for thousands of years with yams and root vegetables supplemented by pigs, chickens, fish from ponds and any number of food items from the rainforest nearby
Some villages in Papua New Guinea are semi-permanent because they are small, the soil supports the food crops, and the nearby forest provides sources of nutrient input and food
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