Nigeria is the most populous country in West Africa, and currently the seventh most populous in the world. About half of Nigerians are urban dwellers. Nigeria’s urban character is unique in Africa, counting 11 cities of over 1 million, and more than 70 cities of over 100,000 inhabitants. Rapid growth in both population and the economy exerts a strong pressure on Nigeria’s diverse natural resources, from the tropical coastal plains in the south to the Sahelian savannas in the north. After running 4,000 km from the Guinean Highlands through West Africa, which makes it Africa’s third longest river, the Niger reaches the Gulf of Guinea on the Atlantic Ocean in Nigeria, where it ends in a network of channels forming a large coastal delta with extensive mangrove and swamp forests. The Niger Delta, which covers about 70,000 sq km, is a hotspot of plant and animal biodiversity, but it also holds Africa’s second largest oil and largest natural gas reserves, which have fueled Nigeria’s economy, the second largest in Africa by nominal gross domestic product (GDP). Diversity and extremes characterize Nigeria both culturally and environmentally, making it a microcosm of all Africa’s promise and problems.