Official language to the government in their native languages. In countries that do not formally designate an official language, a "de facto" national language usually evolves. English is the most common official language, with recognized status in 51 countries. Arabic, French, and Spanish are also widely recognized. An official language that is also an indigenous language is called "endoglossic", one that is not indigenous is "exoglossic". An instance is Nigeria which has three endoglossic official languages. By this the country aims to protect the indigenous languages although at the same time recognising the English language as its lingua franca. Around 500 BC,
Ecoregions of Zambia artificial reservoir), together with the smaller lakes such as Mweru Wantipa and Itezhi-Tezhi reservoir, and numerous lagoons and swamps cover about 5% of Zambia. Together with their associated rivers, the WWF categorises these freshwater bioregions in Zambia: Zambezi Basin made up of (not shown on the map): Ecoregions of Zambia The biomes and ecoregions in the ecology of Zambia are described, listed and mapped here, following the World Wildlife Fund's Global 200 classification scheme for terrestrial ecoregions, and the WWF freshwater bioregion classification for rivers, lakes and wetlands. Zambia is in the Afrotropic biogeographic realm (or ecozone) of the scheme.