Slash and burn farmers in southeast Asia are blamed for deforestation and are considered backward or ignorant. Efforts have been made by agricultural development experts to urge farmers to switch to fixed field methods. Slash and burn methods are used in upland areas with steep slopes, low soil fertility, and unpredictable natural hazards in order to allow survival in an environment made difficult for cultivation by other methods. Slash and burn farmers may be stable or migratory and use rotational or pioneering methods. Rotational methods involve clearing and burning a new plot every year, and then allowing regeneration of forest for 10-20 years. When population density is 40/square km, this method does not degrade the environment. Pioneering involves clearance of primary forest, cultivation for several years until soil fertility is destroyed, and then replacement with low productivity imperata cylindrica grass." Pioneering tends to cause long-term environmental degradation. Humid tropic soils tend toward infertility, and in many areas of southeast Asia the soils are nutrient-poor and acidic. Ash from burning also reduces soil acidity. In northeast Thailand, 454 kg of calcium are released from burning one hectare of mature forest. The advantages are affordable natural fertilization and freedom from technical experts and imported spare parts. Frequent rotation also helps to expand the crops and provide disease protection. Population densities, competition for scarce resources, and social and economic pressures make the slash and burn technique inappropriate. As yet unavailable alternative farming techniques are needed which take advantage of slash and burn benefits. Slash and burn farmers are victims of deforestation even though they may appear to be the villains."
