> It’s no surprise that the region that gave birth to agriculture has also refined innovative sustainable agriculture methods for thousands of years. Pigeon towers were one such innovation—and they helped Persian farmers cultivate all kinds of crops on previously arid, thin-soil land.

Didn't ancient Persia originally have much more fertile soil, but unsustainable practices (like the introduction of goats) destroy the soil quality? I guess both can be true, initial poor practices necessitated the introduction of more sustainable techniques.