Ivory beaches, stretch of land

Devbagh is a tiny island off the west coast near Karwar in the Uttara Kannada district of Karnataka, which has one of India's largest untouched forests and miles of pristine ivory beaches. Hemmed in by the ghats on the east and the Arabian Sea on the west, as a seaside town Karwar offers varied opportunities for the tourist. For a relaxed holiday spent in solitude, however, undoubtedly head for Devbagh, a small island near the confluence of the Kali River and the sea. Devbagh, which literally means "God's own garden", is a 20-minute boat ride from Karwar. Apart from Devbagh, Karwar's other claim to fame is the Seabird Project, the biggest naval base in the whole of Asia. The Rs. 36,000 crore project will turn Karwar and its beautiful locales into an importance centre for the country.
The first sight of Devbagh, a totally isolated stretch of land, makes you feel that you are about to spend the next few days on a private island. You setp off the boativor on to untouched and secluded sands in the midst of casuarina groves.

Could you please explain to me what "ivory beaches" mean in this context?

I know "ivory" means "decorative articles made from elephant's tusks", but I don't know what they mean by "ivory" beaches. Similarly, I guess, "stretch of land" means, "a piece of land".