The Edge of Extinction

Fig.1. The Hainan black-crested gibbon (Nomascus hainanus) is critically endangered with under 30 individuals left in the wild (Credit: MRNS)

With only 26 to 28 individuals left in the forests of southwest China, Hainan gibbons are the rarest primates on Earth. Habitat destruction and poaching have placed this species (Nomascus hainanus) on the cusp of extinction. Ongoing conservation efforts work to protect China’s endangered biodiversity, but tracking species decline is especially difficult. Extinction often occurs over centuries, and the extent of how humans affect animals is difficult to determine without a baseline of past population numbers. A recent study published in the Proceedings of the Royal Society B examined a novel resource in the fight to protect biodiversity and shed light on the decline of gibbon populations over time.

Samuel Turvey at the Zoological Society of London (ZSL) and fellow researchers combed through government records stretching back over 400 years for clues about local gibbon communities. Among descriptions of political changes or shifts in culture were clues about the presence or absence of the rare primate. Unlike other animals, which might not be mentioned in historical records, gibbons are special to southwest Chinese culture, often featured in poetry or literature. Turvey et al. took advantage of this prevalence in written documents and tracked species numbers from the end of the Qin Dynasty in the 1600s to China’s Republican and Communist periods.

The researchers found that serious decline began in the mid-nineteenth century, following a dramatic drop of forest cover. Populations collapsed during the 20th century, with only a few thousand left in the wild by 1950. Now, numbering fewer than 30 individuals, a disease or natural disaster could wipe the species out completely. The documents analyzed in this study were also able to describe the decline of gibbons in specific regions. Turvey et al. discovered that it took about 40 years for a community to become extinct after they were isolated in a specific region. This find puts a limit on the survival of the current community, which was isolated on China's Hainan Island in the 1980s.

Although the situation is frightening for these primates, this study reveals a novel source of information for future conservation efforts. Historical records may lack specific climate data, and questions remain on the accuracy of population sizes, but such a resource could lead to new management of endangered species. Analyzed alongside environmental records, such as tree rings or sediment cores, these types of documents can describe past climate conditions, species ranges, and how humans interact with their environment.

To learn more about historical documents used in scientific study, read these articles about ancient DNA in animal parchments and peat bog cores supporting archaeological evidence.

References:
Turvey, S. T., Crees, J. J., & Di Fonzo, M. M. I. (2015). Historical data as a baseline for conservation: reconstructing long-term faunal extinction dynamics in Late Imperial - modern China. Proc. R. Soc. B., 1299. doi: 10.1098/rspb.2015.1299