Threre is an interesting essay in the Jewish Chronicle entitled "So, what did the Muslims do for the Jews?" (24th May 2012). It argues that the Jews flourished within Muslim communities and may have died out without them:
"Islam saved Jewry. This is an unpopular, discomforting claim in the modern world. But it is a historical truth. The argument for it is double. First, in 570 CE, when the Prophet Mohammad was born, the Jews and Judaism were on the way to oblivion. And second, the coming of Islam saved them, providing a new context in which they not only survived, but flourished, laying foundations for subsequent Jewish cultural prosperity - also in Christendom - through the medieval period into the modern world.
Within a century of the death of Mohammad, in 632, Muslim armies had conquered almost the whole of the world where Jews lived, from Spain eastward across North Africa and the Middle East as far as the eastern frontier of Iran and beyond. Almost all the Jews in the world were now ruled by Islam. This new situation transformed Jewish existence. Their fortunes changed in legal, demographic, social, religious, political, geographical, economic, linguistic and cultural terms - all for the better.
The political unity brought by the new Islamic world-empire did not last, but it created a vast Islamic world civilisation, similar to the older Christian civilisation that it replaced. Within this huge area, Jews lived and enjoyed broadly similar status and rights everywhere. They could move around, maintain contacts, and develop their identity as Jews. A great new expansion of trade from the ninth century onwards brought the Spanish Jews - like the Muslims - into touch with the Jews and the Muslims even of India."
You can read the full article here.