"One of the real obvious services that rivers provide is fertility. If you look at ancient history we notice that a lot of the early civilizations lived along the great rivers, the Nile, the Tigris and Euphrates, and it was because of the fertility that the flooding river during the spring flood pulse, the river flooded into its floodplain and left behind nutrients and a very rich soil. And it's really one of the ecosystem services that we are in danger of losing as we build levees and dikes along our modern rivers. It's a rare floodplain river these days in the world that continues to flood and provide that fertility. It's something we are losing. It's also something that's very important in the delta area or the estuary of a river. When the Aswan Dam was built blocking the nutrients the Nile would normally carry into the Mediterranean the natural fertility of the Mediterranean a lot of the productivity of the Mediterranean was lost. The fisheries have largely disappeared."