According to a comprehensive publication by The Forest Trends Association states that: "nearly half (49%) of all recent tropical deforestation is the result of illegal clearing for commercial agriculture. The study also finds that around half of this illegal destruction was driven by overseas demand for agricultural commodities including palm oil, beef, soy, and wood products. In addition to devastating impacts on forest-dependent people and biodiversity, the illegal conversion of tropical forests for commercial agriculture is estimated to produce 1.47 gigatonnes of carbon each year—equivalent to 25% of the EU’s annual fossil fuel-based emissions"
Since 1997 indonesian law forbids the use of fire to clear land during the dry season (july-october). Companies continue to breach the law. It is claimed that plantation companies were behind 80% of the fires burning in Sumatra and Kalimantan. The Forestry and Plantations ministry had identified 176 companies suspected of using fire to clear land. However they avoid prosecution by using farmers to set the fires under traditional "slash and burn" techniques and then claim that the fires have spread from outside their concessions.
Each province has 30% of its forest allocated for concessions to convert into plantations. Such land conversion has been identified as the major culprit for the fires. The largest fires can be found on the largest concessions. According to the Indonesian Forum for the Environment.
The fall in prices of forest products exacerbates the problem as the plantations attempt to expand output and cut costs including using fire for land clearance. Meanwhile the government lacks the resources for enforcement.
The extent of biomass burning has increased significantly over the past 100 years. It is now recognized as a significant global source of atmospheric emissions, contributing more than half of all the carbon released into the atmosphere (see table left). The burning of tropical savannahs is estimated to destroy three times as much dry matter per year as the burning of tropical forests (Andreae 1991). Only in the past decade have researchers realized the important contributions of biomass burning to the global budgets of carbon dioxide, methane, nitric oxide, tropospheric ozone, methyl chloride and elemental carbon particulates.