A team of scientists from China has used classical Chinese poetry to plot the decline of the Yangtze finless porpoise, the only known freshwater porpoise, over a period of more than a millennium.
The team collected, filtered and manually collated poems containing references to Yangtze finless porpoises. They identified 724 poems containing occurrence records of the Yangtze finless porpoise since the Tang Dynasty (618-907).
The Qing Dynasty (1636-1912) had the most poems with records of Yangtze porpoises (477), followed by the Ming Dynasty (1368-1644; 177 poems), Yuan Dynasty (1271-1368; 27 poems), Song Dynasty (960-1279; 38 poems), and Tang Dynasty (5 poems)
Of these poems, 362 (50 per cent) contained specific location information associated with Yangtze finless porpoise occurrence: 78 per cent of the records (281) mention the porpoise as occurring in the mainstem of the Yangtze, 14 per cent in its tributaries (51), and eight per cent in lakes (31).
The experts then used the occurrence sites mentioned in the poems to map the historical distribution of the Yangtze finless porpoise.
“The number of grids with occurrences declined from 169 in the Tang Dynasty to just 59 in modern times, implying a contraction of 65 per cent of the historical ranges of the Yangtze finless porpoise. Importantly, there was a sharp decrease from 142 grids during the Qing Dynasty to 59 in modern times, suggesting a relatively rapid shrinkage of range over the past century,” the paper noted.
They also found that most of the habitat contraction of the porpoise occurred in the tributaries and lakes, where the species’ range decreased by 91 per cent, while in the main steam, the range reduced by 33 per cent.
Dam building was mainly to blame for the range contraction of the porpoise, the paper stated, as dramatic increase in dam construction during the 1950s blocked movements between tributaries, lakes, and the Yangtze mainstem.
“Our study demonstrates that historical art forms provide valuable information that can be used to track wildlife range changes over time…Besides species distribution, such sources can also provide useful information on climate change, biodiversity loss and natural disasters, making historical documents and art — when used properly — valuable resources for biodiversity studies,” the researchers wrote.
Range contraction of the Yangtze finless porpoise inferred from classic Chinese poems has been published in the journal Current Biology. The authors are Yaoyao Zhang, Jiajia Liu, Shilu Zheng, Jianghua Wang, Kexiong Wang, Ding Wang and Zhigang Mei.