Crinum thaianum

A major threat to the habitat of this species is the dredging of rivers and streams for removal of sediment and rock for construction and land reclamation purposes (this has also increased the speed of water flow in habitats of the Water Onion, where entire subpopulations have been dislodged). Also threatened by diversion of the rivers and streams for agricultural purposes. There is also extensive changes in the ecology of the streams and rivers due to land use changes in the adjoining areas (e.g., clearing of forest for agriculture) and resultant land-based erosion and river bank erosion (the substrate of the Nakha and Kuraburi rivers has changed drastically over the past 10 years, due to erosion. The muddy substrate that facilitates the growth of Water Onion has been replaced by pebbles, rock and gravel, in large areas of these rivers. Collection of bulbs from the wild for sale to the international trade for home fish ponds and aquaria is also a threat which needs closer monitoring.