VEGETATION DYNAMICS IN THE DRY VALLEYS OF YUNNAN,CHINA, DURING THE LAST 150 YEARS: IMPLICATIONS FOR ECOLOGICAL RESTORATION

Abstract

In southwestern China, there are many opinions about past environmental conditions and the historical drivers of change, but little direct evidence. Such is the case in Dry Valley ecosystems, where current conservation programs appear to be based more on subjective perceptions than scientific understanding. Our research objective was to develop an historical profile—the description and explanation of environmental change—for the Dry Valleys to see if today's perceptions about past change are supported by data. Our study area encompassed northwestern Yunnan and adjacent Sichuan and Tibet. Specifically, we assessed vegetation dynamics by comparing historical records from 1868-1949 to conditions in 2001-2005. We used two sources to establish baseline conditions from which to assess change: 28 historical publications and 56 old photographs for which we rephotographed the modern scene. Our major finding is that there has been no substantial change in the cover of Dry Valley vegetation during the last 150 years. We also found that the aerial coverage of crop fields has decreased and major landslide activity was caused by chronic geological instability and infrastructure development. Overall, we found that comparisons of written and photographic records between 1868 and 2005 do not support many common assumptions regarding environmental degradation in the Dry Valleys, upon which current ecological restoration programs are based.