As of July 2024, how many sites are there in the World Network of Biosphere Reserves designated by UNESCO, following the approval of 11 new biosphere reserves in 11 countries, including Belgium and Gambia for the first time, as well as two transboundary biosphere reserves, and the addition of new reserves in Colombia, the Dominican Republic, Italy, Mongolia, the Kingdom of the Netherlands, the Philippines, the Republic of Korea, Slovenia, and Spain, covering a total area of 37,400 km²?