Pollution-sensitive plant expands more than tenfold in Erhai Lake

A pollution-sensitive aquatic plant has expanded across Erhai Lake in southwestern China, offering visible evidence of the lake’s ecological recovery. Ottelia acuminata, a species found only in China, covered about 950,000 square metres in 2026, up from roughly 90,000 square metres in 2021, according to the Erhai management authority. This August, its white flowers spread across parts of the lake.

The plant requires clear, clean water and is used as an indicator of ecological conditions. It had nearly vanished after Erhai began suffering eutrophication in the early 1990s and a major cyanobacterial bloom in 1996. From January through June 2026, water at national monitoring sections remained at China’s Class II standard and was rated excellent.

The return follows years of watershed work addressing sewage, agricultural runoff and damaged habitat. Measures included nearly 30 kilometres of new or upgraded rainwater and sewage pipes, 19 wastewater plants and 92 rural treatment facilities, plus restoration of aquatic vegetation. All 27 major rivers entering the lake have consistently maintained good or excellent water quality. The flowers’ resurgence shows how coordinated repair can bring a sensitive native species back from near disappearance.