Mexico ranks first in the Americas and seventh in the world for the number of UNESCO World Heritage Sites. It is also one of the world's 17 megadiverse countries, ranking fifth in natural biodiversity. Mexico's rich cultural and biological heritage, as well as varied climate and geography, makes it a major tourist destination: as of 2018, it was the sixth most-visited country in the world, with 39 million international arrivals. Mexico is a member of United Nations, the G20, the Organisation for Economic Co-operation and Development (OECD), the World Trade Organization (WTO), the Asia-Pacific Economic Cooperation forum, the Organization of American States,  Community of Latin American and Caribbean States, and the Organization of Ibero-American States.