The Ganges River Delta (fig. 5) is the largest inter-tidal delta in the world. With its extensive mangrove mud flats, swamp vegetation and sand dunes, it is characteristic of many tropical and subtropical coasts. The vegetation cushions the shoreline from wind and wave action while the mangrove trees provide a habitat and food for aquatic and terrestrial plant and animal life. The increasing demand for lumber and firewood is outpacing the natural re-growth of the mangrove trees. Space Shuttle photographs, taken over time, permit monitoring of environmental changes in the delta caused by population pressures, and allows mapping of geological changes caused by shifting distributaries and delta growth. As seen in this photograph, the tributaries and distributaries of the Ganges and Brahmaputra Rivers deposit huge amounts of silt and clay that create a shifting maze of waterways and islands in the Bay of Bengal.