Now if mangroves were grown in places where they do not currently grow at all, why should the subsequent economic harvesting cause coastal erosion? Surely quite the reverse would be the case. And surely if they were economically managed, rather than cut down for free by anyone who can get at them, the owners would look after them carefully regardless of their cultural background.

Mangroves do grow along the Red Sea coast, and Persian gulf coast, so they are native to the region. But they grow only in tiny areas: there are less than 5 sq km of mangrove in Egypt, and are now all protected. There are surely extensive areas that have been lost from.

So there would seem to be scope for expanding their range. Whether it could be an economic project harvesting some of the output, that seems a more difficult question.

In fact people have already tried, and discovered it is not easy. See the wikipedia article Mangrove - Wikipedia, the free encyclopedia near the bottom.

I am not aware of any salt-tolerant bamboo. They also are mostly very thirsty plants, so probably not the best choice for Middle East.