Black swans are being recruited to tackle unwanted water hyacinths.
A black swan breeding base in Qingpu District is using the bird to eliminate the aquatic plants — thereby easing the invasion of unwanted aquatic plants and tackling water pollution.
Water hyacinths are a headache because they block waterways and affect flood drainage.
An adult black swan can eat 2.5 kilograms of water hyacinths daily, according to Huang Haibo, executive director of the Shanghai Wildlife Protection Association.
Shanghai Daqian Ecological Estate, one of the biggest black swan breeding bases in China, has nearly 10,000 of the swans. About 30 percent of their food comes from concentrated feed, with the rest supplied by floating plants like water hyacinths.
Workers at the base salvage the hyacinths from rivers and put them into the estate's lake for the swans, to digest.
When the swans excrete the hyacinths, it then serves as feed for fish, and the expansion of fish will contribute to water purification, said Huang.
This way of killing aquatic plants has been proved feasible by experts of Shanghai Academy of Agricultural Sciences. "We plan to release black swans into rivers filled with water hyacinths, which can ease the invasion of unwanted aquatic plants and tackle water pollution, and provide a solution for the shortage of food for black swans," Huang added.
The city's greenery and public sanitation authorities said the practice will be tested on a small scale initially, but expressed fears that the black swans might be stolen or killed. In April, a black swan in Xujiahui Park was illegally killed and eaten by a migrant worker.
This year, a warm winter and rising tide levels led to an early outbreak of water hyacinths from the usual September to June period.
Some areas in Songjiang and Jinshan districts, Suzhou Creek and upstream Huangpu River have all seen the invasive species.
This year, 147,000 tons of water hyacinths have been removed since June, a record in recent years.
October and November are the peak months of the plant invasion.