River deltas and other low-lying areas are often surrounded by poorly drained mineral beds. This leads to the formation of marshes, large, water-logged areas vibrant with grasses and other plant life. Marshes are often extremely complex ecosystems home to hundreds of different plant and animal species. Rice and other food plants requiring large quantities of water can be grown in marshes, although the soil underneath may not be sufficiently hospitable. Due to the soft nature of the ground, marsh is generally unsuitable for building purposes.