Khat

Khat is a flowering plant native to tropical East Africa and the Arabian Peninsula. It is also known as qat, qaat, quat, gat, jaad, chat, chad, chaad and miraa. The plant is grown commercially in Kenya, Ethiopia, Oman, and Yemen.
Khat is a shrub. When grown commercially, the shrubs grow to a size of about 5m, in the wild they can reach about 20m. 
Khat is used as a stimulant in Eritrea, Somalia, and Yemen the effects are comparable to those of drinking tea or coffee. 
Problems.
There are some problems with Khat. People can become psychologically addicted to the drug. Many anti-drug organisations, such as the Drug Enforcement Administration target this drug. It is illegal to use in many countries, though not in Yemen.
Khat is very popular in Yemen. Much of the country's farming resources are used for it because farmers get more money than for other cash crops. It is estimated that 40% of the country's water supply goes towards irrigating it. Its production is said to increase by about 10% to 15% every year. It uses so much water that groundwater levels in the Sana'a basin are getting lower. For this reason, government officials have proposed to move large portions of the population of Sana'a to the coast of the Red Sea.
Some studies done in 2001 estimated that the income from growing khat was about 2.5 million Yemeni rials per hectare, while it was only 0.57 million rials per hectare if fruits were grown. This is a strong reason farmers prefer to grow khat over coffee and fruits. It is estimated that between 1970 and 2000, the area on which khat was cultivated grew from 8,000 hectares to 103,000 hectares.