Coffea is a genus of flowering plants in the family Rubiaceae. Coffea species are shrubs or small trees native to tropical and southern Africa and tropical Asia. The seeds of some species, called coffee beans, are used to flavor various beverages and products. The fruits, like the seeds, contain a large amount of caffeine, and have a distinct sweet taste. The plant ranks as one of the world's most valuable and widely traded commodity crops and is an important export product of several countries, including those in Central and South America, the Caribbean and Africa. The coffee trade relies heavily on two of the over 120 species, Coffea arabica (commonly known simply as "Arabica"), which accounts for 60–80% of the world's coffee production, and Coffea canephora (known as "Robusta"), which accounts for about 20–40%. Both coffee species are vulnerable to shifting growing zones caused by climate change, likely to result in a decline in production in some of the most important growing regions.