China Battles Alien Marsh Grass 中国发起外来滩涂草治理战

“Mammoth” plan to control a coastal invader would benefit migratory birds. 治理沿海入侵植物的宏伟计划将使候鸟受益。

Along its coastline， China has been taken over by a green invader. Smooth cordgrass （Spartina alterniflora） grows tall and thick across tidal mudflats， depriving endangered migratory birds of habitat， clogging shipping channels， and ruining clam farms. Now， China aims to beat back 90% of the weed by 2025. “This is a mammoth undertaking，” says Steven Pennings， a coastal ecologist at the University of Houston. “It’s audacious.”

中国的海岸线被一个绿色的入侵物种占据。这种光滑的米草属植物叫作“互花米草”，生在潮间滩涂带，长得又高又密，侵占了濒危候鸟的栖息地，堵塞了航运通道，破坏了蛤蜊养殖场。现在，中国的目标是到2025年除治90%的互花米草。休斯顿大学沿海生态学家史蒂文·彭宁斯说：“这是个非常艰巨的任务，非常大胆的设想。”

The nationwide effort， launched in February this year， “is by far the largest action plan for wetland invasive species control in China and even in the world，” says Bo Li， an invasion ecologist at Fudan and Yunnan universities who was not involved in creating the plan. It won’t be simple or cheap， costing hundreds of millions of dollars， Li estimates. And schemes to dig up， drown， or poison the weed all have side effects. “It’s going to be really difficult，” says Sam Reynolds， a biologist at the University of Cambridge.

这项全国行动于今年2月启动。就职于复旦大学和云南大学的入侵生态学家李博说：“这是迄今为止中国乃至世界最大的湿地入侵物种治理行动计划。”李博本人并未参与计划的制定。他认为这项行动没那么简单，费用也不低，估计要花费数亿美元。此外，挖除、淹没或者药杀互花米草的方案都有副作用。剑桥大学生物学家萨姆·雷诺兹说：“这确实会非常困难。”

Spartina， native to eastern North America， was brought to China starting in 1979 to stabilize tidal mudflats and turn them into land for agriculture or development. The plan worked， but the Spartina kept spreading and now covers about 68，000 hectares， about the area of New York City. The government has realized， says Yihui Zhang， a wetland ecologist at Xiamen University， that “the harm of Spartina alterniflora outweighs its benefits.” It dominates native salt marshes， outcompeting native plants that provide food for indigenous species such as the reed parrotbill， which has declined as a result.

互花米草原产于北美东部，自1979年起引入中国，用来稳固滩涂并将其变为农业或发展用地。该计划奏效了，但是互花米草不断蔓延，现在占地约6.8万公顷，大致相当于纽约市的面积。厦门大学湿地生态学家张宜辉说，政府已经意识到“互花米草的危害大于益处”。互花米草成为本地盐沼的主要物种，长势盖过为本土物种提供食物的本土植物，比如震旦鸦雀就因缺少食物而数量减少。

Also at risk are birds migrating along the East Asian–Australasian1 Flyway， “the most important flyway in the world for coastal water birds，” says Nicola Crockford， principal policy officer at the Royal Society for the Protection of Birds. Spartina is the biggest threat to habitat for migratory birds in China because it prevents them from gathering food， Crockford says.

英国皇家鸟类保护协会首席政策官妮古拉·克罗克福德表示，沿东亚—澳大拉西亚迁飞路线迁徙的鸟类也面临危险，“这条路线是世界上最重要的沿海水鸟迁飞路线”。克罗克福德还说，互花米草是中国候鸟栖息地的最大威胁，因为它阻碍了候鸟觅食。

China has already launched smaller scale Spartina control projects. Li was involved in a well-known success at the Chongming Dongtan National Nature Reserve. After Spartina was planted there in 2001， it ruined habitat for dozens of fish species and migratory birds. To remove the weed， engineers built a seawall and flooded the wetland to drown the grass. By 2018， the project had eliminated 95% of the Spartina in 2400 hectares， and native plants and bird populations began to recover. But the price tag was steep： about $150 million， largely for erecting the seawall. A smaller project in Jiangsu had similar success at lower cost by covering Spartina with silt dredged from a shipping channel. In both cases， follow-up weeding was necessary to remove survivors.

中国已经启动了规模较小的互花米草治理项目。崇明东滩鸟类国家级自然保护区就是众所周知的成功案例，李博曾参与其中。2001年，该保护区内种植互花米草后，这种植物破坏了几十种鱼和候鸟的栖息地。为了清除互花米草，工程师们修建海堤，水浸湿地，淹没互花米草。到2018年，该项目在2400公顷的土地上消灭了95%的互花米草，本土植物和鸟类的数量开始恢复。然而，项目造价高昂，大约花了1.5亿美元，主要花在建造海堤上。江苏一个小项目以更低的成本取得了类似的成功，该项目用从航运通道疏浚而来的淤泥掩埋互花米草。这两个案例后续都需要再次除草才能将残余的互花米草彻底清除。

But local control efforts aren’t enough， because the weed spreads so readily. Under the national plan， local authorities will map the distribution of Spartina and work together. Officials in coastal regions submitted control plans to the National Forestry and Grassland Administration， which is overseeing the effort. Funds will come from the national and local governments.

然而，地方治理行动的力度不够，因为互花米草太容易蔓延。根据国家计划，各地方政府将绘制互花米草分布图，然后合作除草。国家林业和草原局负责监管此项计划，沿海地区的官员向该局提交了治理计划。资金将由国家和地方政府提供。

Li says scientists and policymakers have yet to solve a key challenge： identifying the combination of eradication methods that would work best in the variety of habitats Spartina has invaded. None of the possible methods is a sure thing. Releasing insects that eat weeds， a technique called biocontrol， has worked against other plants， but so far researchers have not found anything that can be used against Spartina in China. Other techniques have limitations. Flooding， for instance， can starve the sediment of oxygen， which can kill worms and other animals that live in it. Baoshan Cui， an expert in wetland protection and restoration at Beijing Normal University， says waterlogging causes more problems than other strategies， so it should be avoided. But backhoes and other construction equipment， which can drive onto firm mudflats to dig up and bury Spartina， compact the mudflats， disturbing the habitat of sediment-dwelling creatures. And herbi-cides have rarely been used against Spartina in China.