Tigray, the most northern of Ethiopia's ethnically based regional states, covers an area of 53 386 km 2 and has a population exceeding 5.17 million of whom some 24.3% are urban dwellers. Wide agroclimatic variations result from altitudinal differences (600 to 3000 m) and rainfall patterns. The area is a center of origin of many cultivated and wild plants. The mainly agricultural rural population, farming small areas of non-contiguous plots, makes wide use of these conditions to ensure its livelihood. Crops grown include ten species of cereals, seven pulses (legumes), six oilseeds, and numerous fruits, vegetables and spices. Within these groups and species several varieties or landraces are recognized and used to advantage. Wild species are exploited for food, especially at times of crop failure, and for medicines. Crop production is beset by many biotic (weeds, pests, diseases), abiotic (infertile soils) and anthropic (government policy, civil strife, military actions) constraints. Drought is a frequent occurrence and leads to crop failure and famine. In normal times crop yields are low but some of the production is marketed to provide cash for other necessities. Tigray's population is poverty stricken and often in need of food aid.