BEIJING, May 15 (Xinhua) -- Chinese scientists have mapped the 1,400-year distribution history of the Yangtze finless porpoise through an innovative analysis of classic Chinese poetry. 

Researchers from the Chinese Academy of Sciences' Institute of Hydrobiology examined historical poems to trace the species' habitat changes, providing new insights into long-term biodiversity patterns.

The Yangtze finless porpoise, notable for its relatively large size and frequent surface activity, has long captured human attention. Its distinctive leaping behavior during feeding, especially before thunderstorms, made it a common subject in ancient literary works.

The research team identified, collected and analyzed references to the porpoise in classic poems. By studying poets' biographies, subject matter and writing styles, they mapped the species' distribution across different historical periods and geographic areas over 14 centuries. 

Their systematic examination covered 724 poems dating from the Tang Dynasty (618-907) onward. Documentation peaked during the Qing Dynasty with 477 references, followed by the Ming Dynasty with 177, the Song Dynasty with 38, the Yuan Dynasty with 27, and the Tang Dynasty with five. 

To account for the Yangtze River's geographical transformation and human influence over time, the team created a spatial model dividing the river basin into 1,056 standardized 30-by-30-kilometer grid units for precise historical comparison.

Results indicated a 65 percent contraction in distribution range since the Tang Dynasty, which decreased from 169 grid units to just 59 today. The most severe decline occurred over the past century, shrinking from 142 grid units during the Qing Dynasty to present levels. 

Regional analysis shows uneven habitat loss -- with the main Yangtze waterway seeing a 33 percent reduction, and tributaries and lakes suffering a 91 percent decrease in porpoise presence. 

The study illuminates connections between the development of Chinese civilization and biodiversity changes, which devised innovative approaches to investigating historical animal population dynamics.

The findings were published in the Current Biology journal.