Yemen can be divided geographically into four main regions: the coastal plains in the west, the western highlands, the eastern highlands, and the Rub’ al Khali in the east. The Tihāmah (“hot lands” or “hot earth”) form a very arid and flat coastal plain along Yemen’s entire Red Sea coastline. Despite the aridity, the presence of many lagoons makes this region very marshy and a suitable breeding ground for malaria mosquitos. Extensive crescent-shaped sand dunes are present. The evaporation in the Tihamah is so great that streams from the highlands never reach the sea, but they do contribute to extensive groundwater reserves. Today, these are heavily exploited for agricultural use. Near the village of Madar about 50 km (30 mi) north of Sana’a, dinosaur footprints were found, indicating that the area was once a muddy flat. The Tihamah ends abruptly at the escarpment of the western highlands. This area, now heavily terraced to meet the demand for food, receives the highest rainfall in Arabia, rapidly increasing from 100 mm (3.9 in) per year to about 760 mm (29.9 in) in Taiz and over 1,000 mm (39.4 in) in Ibb. Temperatures are warm in the day but fall dramatically at night. Perennial streams occur in the highlands, but these never reach the sea because of high evaporation in the Tihamah.
The central highlands are an extensive high plateau over 2,000 m (6,562 ft) in elevation. This area is drier than the western highlands because of rain-shadow influences, but still receives sufficient rain in wet years for extensive cropping. Water storage allows for irrigation and the growing of wheat and barley. Sana’a is in this region. The highest point in Yemen and Arabia is Jabal An-Nabi Shu’ayb, at about 3,666 m (12,028 ft).
Yemen’s portion of the Rub al Khali desert in the east is much lower, generally below 1,000 m (3,281 ft), and receives almost no rain. It is populated only by Bedouin herders of camels. The growing scarcity of water is a source of increasing international concern.
Principal agricultural commodities produced in the nation include grain, vegetables, fruits, pulses, qat, coffee, cotton, dairy products, fish, livestock (sheep, goats, cattle, camels), and poultry.
Most Yemenis are employed in agriculture. However, the role of agricultural sector is limited due to the relatively low share of the sector in GDP and the large share of net food-buying households in Yemen (97%). Sorghum is the most common crop. Cotton and many fruit trees are also grown, with mangoes being the most valuable. A big problem in Yemen is the cultivation of Khat (or qat), a psychoactive plant that releases a stimulant when chewed, and accounts for up to 40 percent of the water drawn from the Sana’a Basin each year, and that figure is rising. Some agricultural practices are drying the Sana’a Basin and displaced vital crops, which has resulted in increasing food prices. Rising food prices, in turn, pushed an additional six percent of the country into poverty in 2008 alone. Efforts are being made by the government and Dawoodi Bohra community at North Yemen to replace qat with coffee plantations.