One hundred thousand hectares of estuaries converted in 35 years

April 10 () –

More than 100,000 hectares of estuaries (an area 17 times the size of Manhattan) have been converted over the last 35 years into urban land or agricultural fields Worldwide.

Most of that land conversion and estuarine loss occurred in rapidly developing countries, a new study finds, a study published in the journal Earth's Future.

Estuaries (wetland ecosystems where freshwater rivers meet salty ocean waters) They are gateways that connect land and sea. They provide habitat for wildlife, sequester carbon, and serve as hubs for transportation and shipping.

Humanity has been shaping estuaries to adapt them to their needs for thousands of years and now some countries are paying the price. The degradation and loss of estuaries can reduce water quality, reduce and fragment critical habitats, and eliminate coastal protection from storms.

“The change of estuaries is really interesting, especially in the 20th century, because estuaries have been altered by humans through the construction of estuarine dams and land reclamation,” he said it's a statement Guan-hong Lee, a geoscientist at Inha University in South Korea, who led the study. ““When humans modify estuaries, the consequences of land loss are surprisingly enormous.”

Many developed countries, such as the Netherlands and Germany, have already modified or lost large areas of urban estuaries. Countries with significant modifications to their estuaries could serve as a kind of warning to developing countries, and act early to conserve estuaries It is an opportunity to protect the environmental and economic benefits of developing countriesLee said.

Using Landsat remote sensing data from 1984 to 2019, researchers identified 2,396 estuaries around the world that were large enough to measure with satellite images (those with mouths greater than 90 meters or 295). Almost half (47%) of these large estuaries are located in Asia; The data set includes estuaries on all major land masses except Antarctica and Greenland. They also identified changes in land use, including land conversion and dam construction.

The team then measured the change in the surface of the estuary and compared those changes to where land reclamation and dam construction had occurred.

For the estuaries studied, Between 1984 and 2019, humans converted 1,027 square kilometers (101,000 hectares) of estuaries on urban or agricultural lands in a process called land reclamation, the study found. Land reclamation, which can include drying land and adding sediment to build land, accounted for 20% of the estuary loss. Globally, humans altered 44% of estuaries with dams and/or land reclamationthe study found.

To explore the relationship between estuary gain or loss and economic development, the researchers compared countries' gross income per capita with land reclamation and estuary area. They also analyzed historical maps of high-income countries to find evidence of past alterations of estuaries. and included eight case studies of estuary loss from low-, middle-, and high-income countries.

Middle-income countries lost the most estuarine area during the study period, and almost 90% of all land reclamation (921 square kilometers) also occurred there. “As a country transitions to a middle-income country, tends to increase development“Lee said.

High-income countries lost little estuarine area during the study period. In most cases, that's because the estuary alteration occurred decades earlier, when they were in middle-income and developing states, Lee said. Today, in those countries, attention has shifted from development to environmental conservation efforts: attempts to undo the environmental damage caused by estuary development.

The findings highlight the opportunities developing countries have to minimize the negative environmental and economic impacts of degraded estuaries while balancing their own economic and development needs, Lee said.