For agricultural production they had no choice other than going to marginal lands. And that means erosion. It means destruction of natural resources, cutting of forests and destruction of best ranges in agriculture. Traditionally, nomadic tribes like the Bahktiari and the Gashgaie were perfectly adapted to the fragile mountain terrain. They moved their herds with the seasons, from lowland plains to high altitude pastures.
Nomadic life continues in Iran and the birth rate among tribal people is the highest in the country.
In pastoral production it means the same thing. It means more families, more pastoralists, more herds, which means higher pressure on ranges and, little by little, destruction of the pastures and that itself causes relative poverty, which means going from say sheep to goats, which are easier to keep, and that, again causes more destruction in the pastures. When Syamak Moattari was a medical student twelve years ago, he and three fellow students were worried about pollution in the city where they lived and the mountains where they went climbing. Article 15 of the Iranian constitution prohibits activities that harm the environment, but Iranians, they felt, didn't know enough about the problems. They set up the Green Front of Iran to make people aware of environmental issues.