Guest writer Arthur Karuletwa, director of Starbucks Coffee Traceability, describes coffees Starbucks Reserve coffees from his home of East Africa. SEATTLE, 2016-May-10 — /EPR Retail News/ — Millions of years ago, when the continental drifts split apart from the eastern ridges of the horn of Africa, a geographical masterpiece known as the Rift Valley etched its mark…