In remote China, plant hunters seek clues to climate change
Studying how flowers adapt to global warming in remote China helps scientists consistently demonstrate climate change, say botanists.
Most Mandarin syllables have multiple meanings, so whenever theÂ American ecologist Robbie Hart greets strangers in China,Â he explains the meaning behind Du, his Chinese name.
â€śDu as in cuckoo flower,â€ť he says, referring to du juan hua, the Mandarin term for rhododendron.
In 2009, Mr. Hart began traveling to Chinaâ€™s Yunnan Province to study rhododendrons, a flowering plant with famously pretty flowers. About half the worldâ€™s roughly 1,000 rhododendron species are native to Yunnan and areas of Nepal, Bhutan, and Myanmar (Burma) â€“ a region that was a favorite destination of 19thÂ and early 20th century American and European explorers who traveled east at the urging of Western botanical curators and green-thumbed aristocrats.
Hart, a graduate student at the MissouriÂ Botanical Garden and the University of Missouri, St. Louis, has inspected more than 10,000Â of the explorersâ€™ archived flowers at museums and institutions across Europe and the United States. He is now comparing them with his present-day rhododendron samples. But unlike his footloose predecessors, his aim is to see whether rhododendron behavior during the past century reflects changing global weather patterns.
He is one of a small handful of botanists in the world who study climate change by analyzing how flowering plants are adapting their flowering cycles in response to warming global temperatures. Botanists say such research is important because it draws on little-known historical data to help illuminate the scientific present.
â€śWhen these collections were established, no one really thought about climate change research,â€ť says Richard Primack, a professor of biology at Boston University who studies flowering plants in the US and several Asian countries. But today they help scientists â€śto very consistently demonstrate that climate changeÂ is the new reality.â€ť
Chronicle of flowers
It's rewarding to study plant collections in regions where botanists have made a habit of roaming. Mr. Primack, for example, inspects naturalist records that writer Henry David Thoreau kept of Concord, Mass. Scientists Yasuyuki Aono and Keiko Kazui analyze 9th century chronicles of flowering cherry trees in Kyoto, Japan.
Yunnan Province, which is close to the size of California, is a particularly fascinating place to study flowering plants because its dense jungles and soaring mountain ranges are jewels of biodiversity. According to Sun Hang, deputy directorÂ of the Kunming Institute of Botany, Yunnanâ€™s climate ranges from tropical to arctic, and although it covers just 4 percent of Chinaâ€™s total land area, it contains more than half of the countryâ€™s 16,200 documented plant species.
Western plant hunters began flocking to Yunnan en masse in the late 19th century.Â They typically shipped their flower specimens by ship from Chinese ports to European and American museums or herbariums, or to wealthy Western gardening enthusiasts eager to decorate their lavish estates with flowering exotics.
One such collector, an American named Joseph Rock, was partly based in the Yunnan village of Yuhu from 1922 through 1949 and collected some 25,000 plant specimens, many of which are in collections at Harvard University, in Cambridge, Mass., and the Royal Botanic Garden Edinburgh, in Scotland.
Now Hart, theÂ fourth-year University of Missouri graduate student, is traveling to Cambridge, Edinburgh, and other cities to photograph flower specimens that Mr. Rock collected in Yunnanâ€™s Himalayan foothills. In China, Hart creates spreadsheets of Rockâ€™s data on his laptop and hikes the Himalayas in search of the flowering rhododendrons that his predecessor collected nearly a century ago.
Responding to climate change
How are Yunnanâ€™s rhododendrons responding to climate change? "It gets to be a pretty complicated question,â€ť Hart says on a recent field trip to Yuhu. â€śBut it does look like they are being pushed up the mountain."
Hart, who conducts research in China thanks to roughly $120,000 in grants from the National Science Foundation, says it can be difficult to accurately compare withered flower specimens with living plants. And although he is grateful for the logistical support he receives from the Kunming Institute of Botany, he says, he also struggles to access official scientific data and navigate Chinaâ€™s complex science bureaucracy.
But Hart does have access to villagers from the local Naxi ethnic group. Many of them are keenly aware of rhododendron flowering cycles, and their general impression is that flowering patterns are growing increasingly erratic â€“ an observation that complements Hartâ€™s emerging data sets.
The villagers, though, donâ€™t confirm that rhododendrons are moving higher up in the Himalayas in search of cooler temperatures, as his data suggest. Hart says that is largely because such changes happen over centuries rather than decades, and partly because some villagers donâ€™t know what to make of his scientific inquiries.
â€śWhat are you talking about?â€ťÂ they reply when Hart asks if their rhododendron bushes are traversing mountainsides. â€śTrees canâ€™t walk!â€ť