A self-assembling ecosystem
The floating islands of Indawgyi Lake are buoyant mats of vegetation and peat that drift across the water surface. These formations, known scientifically as sudds, begin with aquatic plants like water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and water fern (Salvinia cucullata) colonizing the lake. Their roots and rhizomes weave together, trapping sediment and decomposing organic matter. Over many years, this process builds up a thick layer of peat, a soil-like material with high organic content.
The buoyancy of these islands comes from their physical structure. The porous peat traps gases, such as methane, released during the decomposition of plant material deep within the mat. This trapped gas acts like a life preserver, keeping the entire mass afloat. The islands are substantial enough to support a succession of larger plants, starting with grasses and eventually including shrubs and trees like teak (Tectona grandis) and various Dipterocarpus species. These larger plants anchor themselves in the dense peat, creating a stable, mobile ecosystem. The entire Indawgyi Biosphere Reserve, which includes the 260-square-kilometer lake, was designated a UNESCO site in 2017.
Islands in motion
Untethered to the lakebed, the islands are constantly moved by wind and the lake's currents, causing the internal geography of the lake to shift with the seasons. This dynamic environment provides a unique and varied habitat for a wide array of wildlife. The submerged portions of the peat mats offer shelter for some of the lake's 93 fish species, including several newly discovered to science.
Above the water, the islands are important for birdlife. Indawgyi Lake is a designated Ramsar site and an Important Bird Area, hosting over 160 bird species. It is a major stopover point on the East Asian-Australasian Flyway for migratory birds. The islands provide nesting grounds for many species, including the critically endangered slender-billed vulture (Gyps tenuirostris) and white-rumped vulture (Gyps bengalensis). The surrounding wetlands and forests also support threatened mammals, such as the eastern hoolock gibbon (Hoolock leuconedys) and the endangered hog deer (Axis porcinus). This interaction between the mobile islands and the lake's broader ecosystem makes Indawgyi a important area for biodiversity.