Yeah, that is a good discussion to have. My first thought was soil depletion due to lack of rotation, but i think that's not so much the case here for (2) reasons. First, i do see them rotate crops occasionally, and that also do crops in "tiers"; beans intermixed with corn, for example, which also replenishes nutrients. The second thing is, if it was just soil depletion, then the folks with the fields at higher elevations would see crop yield decreases as well, not increases.

Having said that, I agree about the deforestation issues. We have lots of landslides around here, and deforestation is largely to blame. Some of the locals (Nas Palas, for example) "get it" about deforestation, and make a point to plant trees on unused acreage.

Also, not much terracing here. That too can cause erosion and nutrient loss. But you can usually identify those cases by large gullies in the hillside/field in question.

Like I said, I am not an agronomist, i am just interested in ag and read books. This kindof learning is a 2-way street. Your points are well taken, though. I do agree that the developing nations shouldn't use a "global problem" to shirk their responsibilities as well.