Our Environment is everything our surroundings comprise of. Human Environment is the interaction between human society and the natural ecosystem. The most fertile regions in the world are the tropical and sub-tropical region. The Ganga-Brahmaputra basin is the largest sub-tropical region in Asia, and the number of people living here is more than anywhere else in the world. Human settlements were the outcome of agriculture, and rivers were a boon for agriculture. The first settlements of human started developing around waterways. The life and culture of people vary in the different natural regions of the world.