Massive diversion project creates conduit for potable water—and possible invaders

China's South to North Water Diversion (SNWD) aims to improve access to potable water for 110 million people by transferring water from the Yangtze River in the south to regions with groundwater deficits in the north. But despite best intentions, human-built infrastructure like the SNWD frequently provides as highly efficient pathways for biological invasion. This study offers the first risk assessment of the world's largest and longest water diversion project potential to spread invasive species.

Alligator weed (Alternanthera philoxeroides), water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes) are aquatic plants whose ranges have strayed far beyond their South American origins to become notorious non-native aliens in China and elsewhere around the globe. Each produces dense mats of vegetation that have the potential to impair navigation and water flow, spawn floods, impact water quality and quantity, and imperil native and agricultural biodiversity.

Using occurrence data from each species' native and introduced ranges accessed via GBIF.org and other sources, the authors constructed ecological niche models underlining their suitability in nearly the entire diversion area. Alligator weed shows the greatest potential for expansion, having already reduced yields of sweet potato and rice by 63 and 45 per cent in the country's south. So as the northerly flow of water from the diversion increases, these models can help prioritize and direct management actions toward the most vulnerable areas where early detection and rapid response could mitigate or avoid the most costly impacts of any invasion.