The widespread failure of slash and burn agriculture.

Slash and burn agriculture and its associated pattern of shifting cultivation have been practised for centuries in all three of the world's great tropical regions.  Under low population pressures in the past, the practice has proved broadly sustainable, but there are notable exceptions to this.  In the leached, acid-soil environments which are typical of the true rainforest zones, many indigenous agricultures of the past are reported to have required fallow periods, between cropping episodes, of perhaps 12-20 years duration. 

It has been observed that, the more acid the soil, the longer the soil needs to recover before the site can be re-burned. Today, the practice is failing widely and leading to the seemingly remorseless destruction of both primary and secondary rainforest; and while it has been reported widely that slash-and-burn practices in the past could guarantee the farmer a food crop, it is also widely acknowledged that the practice maintains them in poverty.  There is no sustainable development pathway open to them and the practice cannot withstand intensification in any conventional sense.  Now, over vast areas of former rainforest, and for perhaps hundreds of millions of subsistence farmers this consumptive process is failing to provide the food security and cash-cropping that are an inherent component of their present day aspirations.  A new set of techniques are urgently required which will be both effective and practical; a set of techniques which will provide food and cash-crop security without exposing the family to debt, dependence or other externalities; and which will not involve them in intolerable workloads in swiddens distant from their homes. 

Slash and burn subsistence versus logging as destroyers of the rainforest.

The destructive effects of over-intensive slash and burn agriculture are exponentially greater than those of logging because the logged-over forest at least contains the seed and root of its own regeneration.  By fragmenting the forest and allowing former forest swiddens to become dominated by invasive grasses, slash-and-burn agriculture not only "closes the door" on regeneration, but also "throws away the key". We are seeing today a slowly enacted environmental and human catastrophe which seldom makes television news headlines.  

Carbon Inputs to the Global Atmosphere.

It is estimated, today, that annual atmospheric inputs of CO2­ due to slash-and-burn agriculture amount to the equivalence of 1.5-2 billion tonnes of elemental Carbon; or about 20-25% of all human-induced inputs.  When it is considered that none of this is effected for its energy release, but solely to create transient fertility for subsistence food-crops, then the irony which is built into the catastrophe becomes apparent.