Jeremy asked recently whether shifting agriculture ((Also called slash-and-burn and swidden cultivation, and tavy in Malagasy.)) can really support growing populations. I’ve just come across (via the PLEC newsletter) a paper from Madagascar ((E. Styger, H.M. Rakotondramasy, M.J. Pfeffer, E.C.M. Fernandes and D.M. Bates 2007. Influence of slash-and-burn farming practices on fallow succession and land degradation in the rainforest region of Madagascar. Â Agriculture, Ecosystems and Environment 119: 257-269.)) which says maybe.
Its objectives
were to analyze jointly with the Betsimisaraka farmers how slash-and-burn practices influence fallow species succession, and how current fallow/cropping regimes influence agricultural productivity and upland degradation dynamics.
The researchers conclude, from discussions with farmers and botanical surveys, that fallow periods have been cut by up to two thirds — to 3-5 years — in the past 30 years. This means that fallow land goes from having plentiful pigeon wood trees on it to bare, dry unproductive grassland in 5-6 rice cropping cycles, after which agriculture is no longer possible. After each cycle, the land needs to be left fallow for increasing lengths of time in order for the soil to recover fertility: “already with the third cycle after deforestation, vegetation starts to degrade quickly in parallel with agricultural productivity decline.”
The findings of this paper indicate that the tavy system with its currently short fallow periods is collapsing.
The main culprit is fire. As fallows become more herbaceous, fire is more difficult to control, and wildfires escape more easily, often “eliminating a productive plot of land for agriculture without getting any benefits of production.”
So what can be done? Try to take fire out of the equation, certainly. “The restoration of soil fertility should build on the biological potential of the system, by optimizing nutrient cycling (e.g. through residue and weed recycling, mulching) and by producing and recycling of high quality organic matter (e.g. through improved fallows and cover crops).” The key to the adoption and success of these practices will be engagement with the young, according to the authors:
The careful development of alternative agricultural practices should especially be done in collaboration with young farmers. If the young obtain a real interest in agricultural intensification, they may not feel the need anymore to leave their native villages and migrate to the forest border to undertake tavy.