Orchid Diversity (Orchidaceae) from Danau Sentarum National Park in West Kalimantan, the largest floodplain lake in Indonesia.

Danau Sentarum National Park located in West Kalimantan is the fifth biggest wetland in Indonesia. This lake is a floodplain/seasonal lake that may vanish for months in the dry season and flood in the rainy season, composing by many small lakes linked together. This outcome is due to the topographical diversity of the national park, ranging from basins to hills, with heights from several meters to approximately 700 m above sea level. In the dry season, the lake is nearly empty as the water drains to the Kapuas River, resulting in grassy terrain and swampy forests. Conversely, in the rainy season, the lake is abundant with water, achieving depths of several meters due to water streams from the nearby hills into the lake's basin. The environment of Danau Sentarum National Park features lowland tropical rainforests and peatlands. Danau Sentarum National Park is a sanctuary for orchids in Indonesia. Numerous orchids thrive on the trees by the lakes. Nonetheless, scant information regarding orchids was gathered from this region. In Danau Sentarum National Park, orchid exploration took place at the end of 2025, resulting in the collection of more than 100 orchid species. The specimens were collected by following the riverside and stopped whenever found the orchid plants. The complete specimens were preserved in ethanol 70% mixed with 5% glycerol, flowers were soaked in a bottle filled in the ethanol solution, and the leaf samples were preserved in silica gel. The preserved specimens were dried in an oven at 60oC and then identified morphologically. Danau Sentarum is a home to numerous endemic species found in Indonesia and Kalimantan. Also, a new finding from the genus Dendrobium increases the diversity of orchid species in both Danau Sentarum and Kalimantan. Lastly, orchid conservation initiatives have taken place through preservation beyond the National Park, such as in living orchid plot exhibits, mainly for national parks’ displays. This mainly involves gathering and identifying the orchids for education and to highlight the iconic species from Danau Sentarum to draw tourists. Nonetheless, it requires a certain period and proper funding to achieve the optimal state necessary for attracting complete focus from the general populace.