People hold surprisingly strong – and often conflicting – views about what causes tropical deforestation. Some blame population growth and shifting cultivation by small farmers. Others focus on misguided government policies and the activities of large companies and wealthy landowners.

To discuss the issue seriously you need real evidence. "Proximate Causes and Underlying Driving Forces of Tropical Deforestation" by Helmut Geist and Eric Lambin pulls together a lot of that. The authors review 152 studies of deforestation in specific regions from around the tropics to assess how important different causes of deforestation really are. The regions vary in size from a single community to several provinces.

In practically all the regions analyzed farmers cleared the forest to plant crops or pasture. In about half the cases commercial logging also played a major role. Shifting cultivation figured in about 40%. Ranching was important in Latin America, but not in Asia or Africa. For fuelwood collection it was the other way around. About two-fifths of the studies reported that poverty contributed to deforestation. A similar number found that powerful public officials and private investors had promoted forest clearing for their own ends.

Among the underlying causes of deforestation, road building, rising demand for cash crops and timber, agricultural colonization programs, subsidized credit, and inappropriate land tenure policies featured prominently. Most of these factors applied to all three tropical continents, although colonization programs and subsidized credit were not so important in Africa. Migration of people into forested areas contributed to forest clearing in a number of places. However, little evidence suggests that high human fertility rates affected deforestation much. A number of studies also highlighted the influence of cultural and technological factors.

So, no matter what you think causes deforestation, you can probably find some place where your argument seems to hold. It all depends on where you look. In most places deforestation has no single cause. It results from a combination of different factors. That also implies that no one universal set of policies can control inappropriate forest clearing. Each region requires its own approach.