by mean temperature of driest quarter, maximum temperature of warmest month, elevation, alluvium soil, land use type and distance to dredging. The lowest contribution was from aspect. (Fig.4) Fig.4 Relative percentage contribution of environmental variables to Water Onion distribution according to MaxEnt model 3.3 The conservation status of the Water Onion plant in Thailand The predicted distributions derived from the MaxEnt was used to evaluate the conservation status for Water Onion because it generated higher accuracy than the logistic regression model. Based on the criterion B1 of the IUCN Red List categories and criteria (IUCN, 2001) Water Onion is categorized as an endangered species. This is due to the fact that the current extent of occurrence covers approximately 126 km2. In addition, it shows a continuing decline during the last decade. Soonthornnawaphat et. al. (2011) reported that suitable habitats of Water Onion covered less than 641 km2. Further evidence showed that Water Onion disappeared from Klong Namdang, Klong Kapur and Klong Tumnung and its population had dropped by 25% during 2008- 2013 (Thailand Institute of Scientific and Technological Research, 2013). Besides, there was an extreme fluctuation in many of number of locations or sub-populations, where water onion could be found in the span of 3 years. That decrease of 80% (Fig.5) could be due to the dredging, land reclamation activities, and the drastic drop of population that reaches the reproductive stage. From this, within a period of 4 years there has been 98% decrease in Klong Naka, 92% in Klong Bangbong, 90% decrease in Klong Nui/Klong Suanyang/ Klong Kumnunhud and 97% decrease in Klong Bangphoamoo (Fig.6). Fig.5 Land use Change in Ranong and Phang-Nga Province, Thailand Fig.6 Extreme fluctuation of sub-populations of Water Onion 34 Proceedings of the International Conference on Climate Change, Biodiversity and Ecosystem Services for the Sustainable Development Goals (SDGs): Policy and Practice 27-29 June 2016, Cha-am, Phetchaburi, Thailand
Proceedings of International Conference on Climate Change, Biodiversity and Ecosystem Services for the Sustainable Development Goals : Policy and Practice 27-29 June 2016 at the Sirindhorn International Environmental Park, Cha-am, Phetchaburi, Thailand
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