Why Did Agriculture in North Africa Collapse after the Islamic Conquest of the region?
A friend and i have been debating the effect of Islam on North Africa and he is of the opinion that the collapse of the North African agricultural heritage is due to Arab influence. He believes that as Arab people are primarily animal husbanders, their influence destroyed the agricultural industry of the region.
The collapse of agriculture in North Africa happened hundreds of years after the original Islamic conquest of the Maghreb. In the early 1000's the Ismaili-Shi'i Fatimid dynasty's authority in the Maghreb began to slip away after they moved the center of the caliphate to Egypt. By 1049 they had lost Morocco, Algeria, and Sicily to foreign invaders and local revolts (whereas at one time they were a credible threat to Ummayyad Spain and southern Italy) — that year the hereditary governors of Tunisia and Libya had enough of this crumbling dynasty and decided to strike out on their own by converting to Sunnism and recognizing the Abbasid caliph in Baghdad. This act greatly angered the Fatimid administration, which then unleashed the fanatically Ismaili-Shi'i Bedouins of the Banu Hilal tribe (translates Children of the Crescent Moon in English) on the inhabitants and agricultural lands of Tunisia and Libya in revenge. Generally, nomads tend to despoil and trash agricultural land during warfare because it's a direct land-use competition, land used for farming often cannot be used for nomadism — so they make the land unfit for agriculture. Another example of a place this occurred is Central Asia, once an area rich in cities and agricultural lands, til the Mongols decided they wanted to pasture their flocks there, impacting the region til this day.
On the other side of the coin, Muslim rule in Iberia and Sicily vastly expanded agriculture in those regions. There the Arabs vastly expanded the irrigation systems, introduced improved farming techniques, and brought new crops. So, the collapse wasn't really due to "the Arabs" or the Islamic conquest, but rather bickering dynasties in the post-conquest era.
Andrew Watson's Agricultural Innovation in the Early Islamic World: The Diffusion of Crops and Farming Techniques, 700-1100.
Fatimid History and Ismaili Doctrine by Paul Walker
Interesting, but which methods were employed to make the land unfit for agriculture? Did they do as the Romans did to Carthage, and salt the lands? Or was the grazing of a massive amount of animals enough to permit desertification?
It was the grazing combined with the destruction of irrigation channels and olive/citrus orchards (trees create moisture and prevent erosion). Also shock warfare on the population.
While Carthage was undoubtedly destroyed, salting the land was a myth popularized in the 19th century (of this current era). Tales of 'salting the earth' are common throughout Medieval times but rarely authentic.
It recalls to mind a quote. As the poet Ennius, who was a young man during the Hannibalic War, had said: "qui vincit non est victor nisi victus fatebur" (He who conquers is not the victor unless the loser considers himself beaten). The tactic of razing a city was uncommon but a fearful tool for propaganda and bargaining. As history turns to myth with the march of time, additional outrages are attributed to the destruction of cities to embellish a good tale.
The question was about the collapse of agriculture, which is not necessarily linked to the increasing aridity. Pastoralism, while bad for agriculture, does not always degrade the environment.
Edit: the destruction of orchards probably had an impact on the aridity, but honestly I don't know if the Hilalian invasion had a climate impact or not (but it certainly had an impact on the number of people engaged in agriculture).
The scholarly debate is whether there was an agricultural revolution under early Muslim rule, not a collapse. Proponents of the theory argue that the spread of Islam allowed crop varieties and farming techniques to diffuse more rapidly, while critics argue that agricultural practices during this period didn't actually change much compared to the Roman period even centuries earlier.
Even if a collapse did in fact occur in the 600-800 time period, a sharp decline in trade routes due to the contraction of the Byzantine empire (or the instability caused by it's contraction) would be a more likely reason than cultural characteristics of the Arabs. The initial Arab conquest of most regions had a very small footprint. Just a few Arab military units and families supported by a minimal tax structure.