Little is directly known from the economic structures of the region due to the paucity of Arab sources. It is however possible to advance a few assertions. The constant warfare between Muslims and Christians and among Muslims certainly costed the region dearly and must have participated to the rampant problems of underpopulation experienced by the Gharb Al-Andalus. As a matter of example, several attempts to repopulate the regions north of Coimbra to guarantee a line of defense against the Christian kingdom failed. The economy was heavily influenced both by structural Islamic habits (creation of cities) and the direction chosen by the dominating Muslim ruler of the Maghrib and al-Andalus. For instance, the great interest paid by the Almohad dynasty to the Atlantic helped develop the military and civilian (trade, fishery) activities of the western Iberian ports such as Sevilla, Lisbon, etc. Despite a general impression of sustained development, specially during the 10th and 11th centuries when the area witnessed a noticeable demographic expansion, the Gharb al-Andalus also underwent some dramatic episodes such as the great famine of 740 which decimated the Berber colonists of the Douro region.