An accidental geoengineer
In December 1979, scientists intentionally introduced a foreign grass to China's coast. The plant, smooth cordgrass (Spartina alterniflora), is native to the Atlantic coast of the Americas. The hope was that this salt-tolerant plant would protect coastlines from erosion and help build up new land on the vast tidal flats. It worked far better than anyone anticipated. The grass is a powerful "ecosystem engineer," physically altering its environment. Its dense stems, which can grow up to two meters tall with up to 200 stalks per square meter, slow down tidal currents. This causes suspended sediment to fall out of the water and accumulate. Its extensive underground root systems, or rhizomes, then bind the new mud, raising the elevation of the marsh.
This process dramatically accelerates coastal accretion. In some areas, marshes dominated by S. alterniflora have advanced seaward by nearly a kilometer in just nine years. This rapid land creation transforms the very geography of the coast, turning open mudflats into dense grasslands. By 2015, the grass had expanded to cover over 50,000 hectares along China's coast. The process is pronounced in the Yellow River Delta, which is part of the Shandong Peninsula's coastal system. The river deposits enormous quantities of sediment naturally, and the introduction of S. alterniflora has amplified this effect.
The ecological cost of new land
The success of Spartina alterniflora has come at a high price for native ecosystems. The aggressive invader has displaced native salt marsh plants, such as Suaeda salsa and the reed Phragmites australis. As a C4 plant, S. alterniflora has a higher photosynthetic rate than many native C3 plants, giving it a significant competitive advantage. The dense meadows it creates transform the habitat entirely. Open mudflats, critical foraging grounds for millions of migratory shorebirds on the East Asian-Australasian Flyway, disappear under a carpet of grass.
This habitat conversion has led to a significant decline in biodiversity. The dense root mats and altered sediment structure affect benthic organisms—the crabs, worms, and shellfish living in the mud—which form the base of the food web. In response to the damage, China officially labeled the grass an invasive species in 2003. Large-scale eradication projects began, particularly after 2021. In Shandong Province alone, the total area covered by the grass was reduced by over 97% between 2020 and 2024, from 8,537 hectares to just 232 hectares. Methods include mowing, flooding, and physical removal, with the goal of restoring the original mudflat and salt marsh habitats.