Without trees, soil is eroded during the monsoon rains - or so the theory goes. The mountains are left naked and the plains below are flooded. His study of local agriculture reveals very little reduction in forest cover in the past 50 years. It is not even clear that deforestation is bad, he says. And some flooding is essential for the peasants of Bangladesh s lowlands.
Normal floods supply the moisture and silt necessary for cultivation.
When the floods cease entirely, the moisture and silt are cut off - damaging local farms. This happened when foreign experts persuaded Pakistan to build huge embankments to protect 30 per cent of the country s flood-prone area in the 1960s. The Government plans more. But the farmers don t like the measures. And the embankment walls are also quickly eroded by heavy sediment in Bangladesh s rivers.