Sand mining led to loss of habitat & range of the porpoise species but there is hope
Photo: iStock_ Checking sand mining can help the population of the critically endangered Yangtze finless porpoise to rebound, scientists found.
Previous reports had shown the cetaceans were pushed out of certain stretches of their habitat due to sand mining. This divides up the population and increases stress among the individuals, especially during pregnancy, the new research done in the Dongting lake in China that joins the Yangtze river found.
Gaps between porpoises in the lake reached 27 kilometres in 2009, the study published in Proceedings of the Royal Society B: Biological Sciences journal January 11, 2023 showed.
“This is over a third of the porpoise's entire range in the lake,” the scientists observed based on surveys between 2006 and 2019 in Dongting.
The Yangtze finless porpoise belongs to the group of animals which also includes dolphins and whales. It is the only freshwater porpoise in the world and breeds just once in 18 months. Overfishing, increased shipping traffic and noise pollution have all been linked with the decline of the porpoise.
It is the most critically endangered of its taxonomic group and the species has an 86 per cent chance of becoming extinct in the next century, according to a 2012 study.
“It's not that long since the Yangtze River dolphin was lost, and we don't want this porpoise to meet the same fate,” said Richard Sabin, principal curator of mammals, Natural History Museum, told Phys.org, a science news website.
The lake is connected to the main body of the Yangtze river by a channel that runs under the Dongting Lake Bridge. The porpoise population would swim to and from the river through this channel but because of sand mining, they were not seen in this channel any longer, the report noted.
“The sheer number of mining boats on the water meant that they formed an effective barrier across the waterway, which could also prevent the porpoise's prey fish from reaching the lake,” the authors added.
Thus, mining activity posed multiple challenges to this endangered species. However, since sand mining was banned in the region in 2017, the porpoises were spotted in parts of the lake they would previously avoid, according to the findings of the survey.
“The suspension of sand mining in 2017 was a very positive move, and could give this important ecosystem a chance to recover,” Sabin said.
More recently, the Chinese government announced a crackdown on illegal sand mining along the river's entire length, Phys.org reported. This could pave the way for a healthy recovery of the cetacean population here.
Mining-induced loss of near-shore habitats, a critical foraging and nursery ground for the porpoise, occurred in nearly 70 per cent of the water channels of our study region, the authors of the report noted.
Sand mining, which has tripled in the last two decades, is an emerging concern for global biodiversity, they added. “Over 50 billion tonnes of sand is mined every year.”
The menace is most rampant in Asia, Africa and Latin America. It threatens biodiversity and interferes with ecological processes through “direct physical disturbances, habitat degradation and reducing water quality by altering sedimentation”, the report stated.
Higher urbanisation has made sand the second-most extracted natural resource in the world after water.
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