Rice paddies cover more than a million square kilometres mostly in tropical to warm temperate climates, especially Southeast Asia. They are filled by rainfall or river water diversions. Their levees and channels retain shallow water areas, with nutrients inputs from inflows and fertilisers. Planting and harvest establishes a regular cycle of disturbance, with many paddies also supporting production of fish and crustaceans, Their simple foodwebs are adapted to temporary flooding and the harvest cycle, including algae and plankton, waterbugs, frogs and waterbirds.