Damage to China’s wetlands by invasive cordgrass highlights fight against biodiversity loss

·4-min read

Invasion by exotic cordgrass has hampered the conservation of native wetlands in China’s major protected coastal areas, an international team led by Fudan University’s coastal ecology lab found after analysing three decades of data.

They found that cordgrass had invaded four out of seven of the largest coastal wetland protected areas in the country. All are along the Yellow Sea coastline in northeastern China and have been established for at least 20 years.

In the Shanghai Jiuduansha Wetland National Nature Reserve, for example, the area of cordgrass grew from 2.33 sq km (0.85 sq miles) in 2000 to 55.7 sq km (21.5 sq miles) in 2018 after being introduced in 1997.

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Cordgrass is native to North America and was introduced to China’s coastlines in 1979 to help prevent erosion and stabilise shorelines because of its tolerance for fluctuating water depth and salinity.

But in 2003, China listed it as an invasive alien species, noting that it “threatened native coastal ecosystems and caused large areas of mangroves to disappear”.

The researchers said controlling the invasion of exotic species and restoring native species were needed to avoid large-scale, long-term dysfunction of protected zones. Establishing these zones is a key biodiversity target in the coming decade.

They also advised against bringing in highly invasive foreign species in the future for local plants and animal habitats to be protected.

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“Although protected areas have been achieving success in slowing reclamation-driven loss of iconic wetlands and critical shorebird habitats, this success is being counteracted by escalating exotic plant invasions,” the team wrote in an article published in the peer-reviewed journal Science Advances on Wednesday.

While cordgrass had been intentionally planted inside and outside some protected areas, the “notorious coastal plant invader” had naturally dispersed into those zones, most likely via waterborne seeds and rhizomes, according to the study.

The team found that exotic cordgrass invaded and often irreversibly replaced critical shorebird habitats, including mudflats and the distinctive “red beach” landscape formed by a native red succulent called Suaeda salsa .

Compared with many native marsh plants, exotic cordgrass is a superior competitor, more tolerant of flooding and wave stresses and more capable of trapping sediments, according to the paper.

Co-author He Qiang, professor of coastal ecology at Fudan University in Shanghai, said China would not see cordgrass completely removed from its soil in the near future because the plant had spread to a vast area.

Native “red beach” marshes in the Yellow River Delta National Nature Reserve, China. Exotic cordgrass invades and often irreversibly replaces critical shorebird habitats, such as the red beach. Photo: EurekAlert
Native “red beach” marshes in the Yellow River Delta National Nature Reserve, China. Exotic cordgrass invades and often irreversibly replaces critical shorebird habitats, such as the red beach. Photo: EurekAlert

“Protected areas are intended to safeguard the habitat of indigenous plants and animals and the native biodiversity, not introduced species. We should do more and prioritise these areas to remove cordgrass from them as soon as possible,” he told the Post.

“It would be a pity to see the red beach scenery we enjoy very much disappear,” he said, pointing to wetlands being turned into “green deserts” avoided by waterbirds after being dominated by cordgrass.

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In the ongoing United Nations Biodiversity Conference hosted in Kunming in southwestern China’s Yunnan province, Beijing pledged to roll out a more ambitious national action plan on biodiversity conservation and donate 1.5 billion yuan (US$232.5 million) to set up a new fund to help developing countries protect the variety of plant and animal life around the world.

The second session of the COP15 conference will take place next spring when the parties to the UN Convention on Biological Diversity are expected to adopt a post-2020 global biodiversity framework that aims to reverse biodiversity loss during this decade.

One of the 2030 action targets is to ensure that at least 30 per cent globally of land areas and of sea areas are conserved through effective and fair management of protected areas, according to a draft of the framework.

He at Fudan University said the study showed that the management of protected areas worldwide should include and strengthen the control of invasive species.

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“It is important to expand the area and number of protected zones and invest more in human resources,” he said. “But this is not enough.

“We need to strengthen the control of invasive species in protected areas, particularly to enhance the monitoring along the borders of protected areas to prevent invaders from spreading into the zones.”

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