Read this passage from "Dover Beach." What do the retreating waves symbolize to the speaker?

The Sea of Faith

Was once, too, at the full, and round earth's shore

Lay like the folds of a bright girdle furled.

But now I only hear

Its melancholy, long, withdrawing roar,

Retreating, to the breath

Of the night-wind, down the vast edges drear

And naked shingles of the world.

The loss of faith

The danger of the wind

The evils of Empire

The joys of love