Rising seas threaten spread of marine invaders, scientists say

PARIS – Sea-level rise driven by climate change could help invasive marine species spread into newly flooded coastal areas, threatening biodiversity and some economic activities, researchers warned in a study published on Sept 28.

The findings in Nature Ecology & Evolution highlight the links between the climate and biodiversity crises, with global warming altering ecosystems and creating new opportunities for non-native species to thrive.

That could “potentially expose ecosystems and human activities that have not previously been affected by these species,” said study co-author Xuan Liu of Beijing Normal University.

The researchers modelled the potential future spread of 122 established non-native marine animals, including fish, crustaceans, molluscs and sea stars, under different climate and sea-level scenarios.

Climate change causes sea levels to rise through thermal expansion – ocean water increases in volume as it warms – and the melting of glaciers and ice sheets.

Global sea levels are projected to rise by about 20cm by 2050 and 56 cm by 2100 under a scenario of moderate growth in greenhouse gas emissions.

That would see around 360,000 sq km of coastal land flooded by mid-century, rising to 550,000 sq km by the end of the century.

More than two-thirds of the newly flooded coastal land – roughly 290,000 to 470,000 sq km – could become suitable for the marine non-native animals studied, particularly around estuaries at mid-latitudes, the authors found.

The risk is concentrated in regions including the eastern United States, Gulf of Mexico, North Sea, Gulf of Guinea, Arabian Gulf, northern Bay of Bengal, south-eastern China and northern Australia.

Several species examined are already established in Europe, including the Pacific oyster, Atlantic blue crab and the veined rapa whelk, a predatory sea snail.

“Estuaries are particularly at risk because they are directly connected to the ocean and are also major hubs of human activity,” Liu said.

Such areas could provide stepping stones for marine invaders moving further inland as the sea advances, the study said.

The findings come as governments prepare for two UN-backed international summits on the twin biodiversity and climate crises: COP17 in October and COP31 in November.

A global assessment by the UN’s expert scientific panel on biodiversity, IPBES, estimated that economic costs from biological invasions exceeded US$423 billion in 2019. AFP