Yemen is by far the most fertile part of the Arabian peninsula, yet agriculture is a hard scrabble. There are two major regions: the smaller coastal region or Tihama and the more extensive mountainous highlands. The Tihama is a narrow, hot, humid semi-, desert, almost waterless an strip that extends the entire seacoast from Maydi on the northern frontier Saudi Arabia to the Bab al Mandab at with the country's southern limits and occupies approximately 10% of the country. These 20,300 sq. Km. miles are watered principally by seven major wadis carrying runoff from the highlands. Their waters seldom reach the sea and rarely flow throughout the year. The climate is oppressively topical. Temperatures often reach 55 degrees c. and even in the cool season range into the 30's, humidity readings of 80% or more are not uncommon. Rainfall in the wetter areas of the Tihama only rarely exceeds 300mm annually. Natural vegetation is sparse and the area is subject to severe windstorms and shifting sands