One advantage coastal countries of west africa have over nations of the sahel is

better transportation
political stability
access to the ocean
larger populations

access to the ocean

Explanation:

Western Africa consists of 16 countries and has an estimated population of 381 million. Owning to the closeness of the ocean they have large biodiversity and as compared to the semi-arid conditions of the Sahel regions. The northern border of the Saharan landscape is a desert environment, also owing to this they have a navigation and transportation route well established along the coastlines. Coastal lands are enriched with the mineral wealth of the nation such as the gold deposits.

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