HODEIDA, YEMEN — The country of Yemen, known in the medieval period as “Green Yemen,” is one of the most extensively terraced areas of the world. There, Yemeni farmers transformed rugged mountain slopes into terraces and built dams like the Great Marib, a structure whose history spans long enough that it was mentioned in the Quran. During the medieval period, Yemen had one of the widest ranges of agricultural crops in all of the Middle East.