Lauren Fuge
“Porpoises chased moonlight on silvered tides, as dragons summoned storm-clouds loom in sight,” wrote Qianlong, prolific poet and emperor of the Qing Dynasty, on a trip down the Yangtze River around 1745.
He was referencing a sighting of the Yangtze finless porpoise (Neophocaena asiaeorientalis). But little did Qianlong know that more than 300 years later, this porpoise species would be critically endangered, and scientists would draw on his poems to help piece together the species’ historic range.
A new study, published in Current Biology, uses ancient Chinese poems to document the decline of the Yangtze finless porpoise (Neophocaena asiaeorientalis) over the past 1400 years. The team searched through historic collections to compile 724 poems that reference the river porpoise.
Analysis shows that the porpoise’s range has declined by at least 65% over that time, with an acceleration in decline over the last century.
“We’re connecting 2,000 years of Chinese culture with biodiversity,” says co-author Zhigang Mei of the Chinese Academy of Sciences. “Our work fills the gap between the super long-term information we get from fossils and DNA and the recent population surveys. It really shows how powerful it can be to combine art and biodiversity conservation.”
The Yangtze finless porpoise is a charismatic cetacean, with a bulbous head and a smile-like expression. It is critically endangered, with 2023 estimates putting the species’ total population at just 1279 animals.
The porpoise only lives in the middle and lower sections of China’s Yangtze River, which is Eurasia’s longest river, spanning 6300km.
For thousands of years, the river has played a key role in China’s culture and economy, used for water supply, irrigation, sanitation, industry and war. People have also historically used the river and its tributaries for transportation, including poets, who often travelled by boat and meticulously recorded their experiences.
And along the way, these travellers would have seen the river porpoise.
“Yangtze finless porpoises are pretty big, and they’re active on the surface of the water, especially before thunderstorms when they’re really chasing after fish and jumping around,” says Mei. “This amazing sight was hard for poets to ignore.”
Mei and team found hundreds of references to river porpoises in poems dating back to the year 618.
“We had to figure out how accurate the poets were being,” Mei notes. “Some might have been really focused on realism, describing what they saw as objectively as possible. Others might have been more imaginative, exaggerating the size or behaviour of things they saw.
“So, once we found these poems, we had to research each poet’s life and writing style to make sure the information we were getting was reliable.”
Of the 724 poems more than half of were written during the Qing Dynasty (1636–1912), while the time period with the fewest porpoise references (just 5 poems) was the Tang Dynasty (618–907), though this may be due to a lack of records.
Half of the poems contained information about where the porpoises were seen.
The team used this information to reconstruct the porpoise’s habitat distribution throughout time.
The results: the porpoise’s range in the main part of the river has decreased by 33% since the Tang Dynasty, and its range in the Yangtze’s tributaries and lakes has decreased by 91%. But the steepest decline in range has occurred in the last century, since the end of the Qing Dynasty.
This lines up with previous research that attributes the porpoise’s decreasing population to human activities along the river, especially hydraulic engineering projects like building dams.
The study demonstrates that poetry can be a useful historical document to help track wildlife range changes over time.
“Protecting nature isn’t just the responsibility of modern science; it’s also deeply connected to our culture and history,” says Mei. “Chinese poetry, this ancient art form, can be a serious scientific tool. Using the past to understand the present, ‘decoding’ the stories behind the art: it’s not just research, it’s like having a conversation with the poets of the past.”