About 4,000 sq km of tidal wetlands lost in 20 years

Study by experts in Britain and Australia reveal that three-quarters of the wetland decrease happened in Asia



File photo
File photo

By Prasun Sonwalkar

Published: Fri 13 May 2022, 7:21 PM

A new study by experts in Britain and Australia based on an analysis of over a million satellite images has revealed that 4,000 square kilometres of tidal wetlands have been lost globally over 20 years, mostly in Asia.

The tidal wetlands – tidal marshes, mangroves and tidal flats – lost were: 13,700 sq km, which was offset by gains of 9,700 sq km, leading to a net loss of 4,000 sq km over the two-decade period.

About three-quarters of the net global tidal wetland decrease happened in Asia, with almost 70 per cent of that total concentrated in Indonesia, China and Myanmar, the study published on Friday in the journal Science said.

Ecosystem restoration and natural processes are playing a part in reducing total losses, but efforts to estimate their current and future status at the global scale remain highly unclear due to uncertainty about how tidal wetlands respond to drivers of change.

The researchers developed a machine-learning analysis of vast archives of historical satellite images to detect the extent, timing and type of change across the world’s tidal wetlands between 1999 and 2019.

“We found 27 per cent of losses and gains were associated with direct human activities, such as conversion to agriculture and restoration of lost wetlands,” said Nicholas Murray, head of James Cook University’s Global Ecology Lab, who led the study.

All other changes were attributed to indirect drivers such as human impacts to river catchments, extensive development in the coastal zone, coastal subsidence, natural coastal processes and climate change.

“Asia is the global centre of tidal wetland loss from direct human activities. These activities had a lesser role in the losses of tidal wetlands in Europe, Africa, the Americas and Oceania, where coastal wetland dynamics were driven by indirect factors such as wetland migration, coastal modifications and catchment change,” said Murray.

Noting that over one billion people live in low-elevation coastal areas globally, the study said that tidal wetlands are of immense importance to humanity, providing benefits such as carbon storage and sequestration, coastal protection, and fisheries enhancement.

“Protecting our coastal wetlands is critical to supporting coastal communities and the wider health of the planet. These areas are the last refuge for many plants and animals,” said Thomas Worthington, Senior Research Associate in the University of Cambridge’s Department of Zoology and co-author of the study, adding: “This data can help identify coastal areas most impacted - and therefore in need of protection, or areas where we can prioritise restoration.”


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