Danica Anderson of the Missouri Botanical Garden in St Louis and colleagues compared plants growing in the "Medicine Mountains" in the north-west of China's Yunnan province with those in non-sacred areas.

The sacred spots abounded with rare plants both in types and number, and also in plants Tibetans use for everything from household brooms to traditional medicines (Biodiversity and Conservation, DOI: 10.1007/s10531-004-0316-9).

There are several possible explanations, says co-author Robert Moseley of the Nature Conservancy in Yunnan, China. "Did the people who set up this sacred landscape choose areas that were inherently richer? Or are the areas less used?"

Local people observe different hunting and tree cutting restrictions in sacred areas, which could afford protection, and the finding presents a conservation opportunity, says Moseley. "Preserving the cultural landscape and biodiversity are in sync." Local Yunnan officials are starting a pilot programme to fold sacred sites into conservation efforts.