I agree with Emmet Scott in general about the disastrous impact of the Arab/Muslim invasion on the Middle East and North Africa and on civilization in general. Moreover, to use currently fashionable terminology, traditional Arab/Muslim society was an occupation regime. Consider the importance of jizya as well as kharaj [a tax specifically on agricultural land, on farmers].  Living off of the conquered peoples --who were not Muslim initially-- was the rule in Muslim lands up to when non-Muslim powers conquered or exerted influence in favor of non-Muslim subject peoples, the dhimmis. And as Scott says, there was tremendous pressure to convert in order to escape exploitation, humiliation and oppression. But as the dhimmi part of the population was reduced by conversion and other ways, the Muslims could no longer depend on the dhimmis for support. And on their own, Muslims have seldom been able to build prosperous economies, certainly not without dhimmis.

I think that it can fairly be said Islam brought down civilization in the conquered lands and it still impedes development in the Islamic world.

My disagreement with Scott is that the final destruction of the irrigation systems in North Africa and the Middle East came several centuries after the conquest. In NA, this destruction is often attributed to the Bani Hilal tribe who migrated westward from Egypt about the 11th century [maybe 10th or 12th], in huge numbers, wrecking the foggaras of the water system on their way. They were followed by another tribe maybe a century later which finished the work.

In Mesopotamia, with a prosperous agriculture between the two rivers, many of the farmers Jews, the ancient irrigation system was wrecked not by Arabs but by the later Mongol invaders. But subsequent Muslim rulers never rebuilt the ancient  irrigation works.  So I am sure that agriculture started to sharply decline when the jizya and kharaj were imposed, yet the final blow to irrigation came a few centuries after the conquest.

By the way, the American agronomist and water supply specialist, Walter Clay Lowdermilk, wrote a book reacing similar conclusions to Scott's about agriculture, although in gentler terms than Scott expresses. Lowdermilk's book was specifically about Israel [Palestine, Land of Promise]. But I feel that in 2011/2012, it is too late to state these matters gently.

The Camel and the Wheel by Bulliet also addresses the issue of the disappearnce of the wheel from the Middle East.