the study, published This week in the magazine Nature SustainabilityAnd the I found it The land is sinking rapidly especially in coastal cities built on “flat and low-lying river deltas”, where groundwater and oil extraction are driven by rapid growth and urbanization.
Led by Singapore’s Nanyang Technological University (NTU), a group of international scientists used satellite imagery taken between 2014 and 2020 to analyze land sinking across 48 of the most densely populated coastal cities, with a population of at least 5 million, worldwide. around the world. They found that the average speed of land subsidence – the rate of land sinking – in each of the 48 coastal cities ranged as high as 16.2 mm, or more than 0.6 inches per year.
“When large amounts of water are drawn from underground, sediment builds up and begins to sink in on itself due to less water trapping the sediment, causing the earth to sink,” said Sherrill Tay, a doctoral student in earth sciences at NTU. and lead author of the study.
The study showed that cities in Indonesia, Myanmar and India also had some of the highest rates of land subsidence. Washington was among the 48 coastal cities studied, but the rate of land subsidence is relatively low – an average of zero millimeters per year – and they are less likely to be affected by rising sea levels.
The findings in the report also take into account and provide speeds for neighborhoods in the interior, where sea-level rise continues to affect residents through extreme weather events, such as hurricanes, cyclones and floods.
“This study is important because it identified land subsidence into a globally consistent matter, which can be used to improve estimates of sea level rise,” said Emma Hill, a professor of Earth sciences at NTU and one of the report’s authors.
The researchers did not investigate the causes of the Earth’s subsidence as part of the scope of the study.
Jakarta, one of the fastest sinking cities, is It is set to be replaced as the capital of Indonesia After years of rapid growth, congestion and pollution. In January, the Indonesian government passed a law outlining how it plans to relocate the capital to a forested region in East Kalimantan, Borneo – a decision environmental activists say will spur further deforestation.
“By 2030, much of Jakarta will be uninhabitable,” said Kian Goh, an architect and urban planner who researches how cities in the United States and Southeast Asia are responding to climate change. “The root cause of land decline in cities is development combined with a lack of proper planning.”
Goh said that while the study is useful in giving readers a “overview” of coastal cities most vulnerable to land subsidence, it does not disentangle the systemic problems that increase risks in those areas. “The places with the highest land subsidence are often home to poor people who live in settlements dating back to the colonial era,” she said. “These are more dangerous areas, where people are suffering the most.”
Goh said drilling wells and extracting groundwater would not be necessary if cities had enough pipes and municipal water supplies. “The problems are ultimately due to matters of planning and policy.”