There are four surviving species of gibbon in China today (eastern hoolock gibbon Hoolock leuconedys; black crested gibbon Nomascus concolor; Hainan gibbon N. hainanus; Cao Vit gibbon N. nasutus), all of which are threatened with extinction. In order to gain a better understanding of the processes that led to their heightened risk of extinction Sam Turvey, Jennifer Crees and I carried out an analysis of historical gibbon population records found in local Chinese gazetteers, dating back from the 1600s (the ‘Late Imperial’ period) to the present day.
We found that northern and eastern gibbon populations disappeared first, followed by a progressive range contraction towards southwestern China (which is consistent with the ‘contagion model’ of range collapse). This pattern of loss can be explained by known patterns of regional human population density and demographic expansion during the Late Imperial period. Historically, northern China accommodated higher human population densities, followed by a migration of the ‘Han’ people to areas south of the Yangtze river from the mid-1500s onwards. Next, there was a westward expansion of people away from areas of high population density in the southeast, which lead to the progressive colonization (and encroachment on gibbon habitat) of the southern uplands by Ming and Qing Dynasty settlers (so-called ‘shed people’).
Our study also highlighted a significant increase in the rate of gibbon population extirpation across China from the second half of the nineteenth century onwards, most likely in response to the well-documented destructive environmental policies and human population explosion that occurred during this period. Finally, our analyses identified that gibbon populations occurring at lower elevations in China have been more vulnerable to extinction as a result of greater historical human population growth and habitat conversion in these more accessible regions. In fact, today’s populations are largely restricted to medium/high-elevation montane forests.
In addition to documenting the dynamics of past gibbon extinctions, we hope that our analyses of long-term Chinese gazetteer records can provide some important historical insights to inform conservation management of the country’s highly threatened remnant gibbon populations.
Reference: Turvey, S. T., Crees, J. J., and Di Fonzo, M.M.I. Historical data as a baseline for conservation: reconstructing long-term faunal extinction dynamics in Late Imperial–modern China. In press in Proceedings of the Royal Society B.
This study was reviewed by the BBC on 5/08/15: http://www.bbc.com/news/science-environment-33776466