The secret life of ancient trees

In Bidoup-Nui Ba National Park, researchers have been able to get reliable climate data for the past 722 years using Fokienia tree ring data. Coupled with research that Buckley conducted in Thailand, he and his colleagues have established tree ring chronologies indicating severe periods of drought across mainland Southeast Asia in the early 1400s.

During this period, the ancient city of Angkor in present-day Cambodia went into rapid decline. While some historians have blamed this on invasions by the rival kingdoms of Siam and Champa, another possibility is that Angkor’s canals and reservoirs ran dry. That would have ended an ambitious expansion that had exhausted the available farmland. A second prolonged drought in the 18th century, which was noted by foreign visitors to Siam, coincided with political upheaval, including the sacking of the Siamese capital by Burmese invaders.

The causes of drought in Southeast Asia are complicated and still far from being understood. El Niño (the periodic warming of the eastern Pacific Ocean) causes a weaker southwest monsoon and a longer dry season in Asia. La Niña, which occurs when sea temperatures cool in the Pacific, triggers a heavier Asian monsoon. Sea surface temperatures in the Indian and Pacific oceans also have an effect.

Anchukaitis likens all this to watching a game of chess. “It’s not simply that we want to understand the rules of the climate system.... We want to understand how those rules interact,” he says. “In chess, each move that a player makes in the game is going to influence the subsequent move, so there are long-term consequences of each individual move.”

Having reliable climate data for only a short time span is like watching a single chess move, he says. That’s why the paleoclimatic data obtained from tree rings is so important. Pushing back the timeline through the tree rings of Fokienia hodginsii enables researchers to see past climate variability and to continue to build their understanding of the interaction between different regions and how they affect the Asian monsoon.

After four physically grueling days, the team has been able to accomplish all of its goals for the expedition. Researchers have collected nearly 100 core samples, developed a new site for study that Buckley believes will push the climate chronology back past the 700-year mark, and have reinforced the collaborative spirit that the team shares with its Vietnamese counterparts.

“I look at this site and I look at Southeast Asia – Vietnam in particular – and I could easily see working here until I’m incapable of working anymore,” Buckley says. “There is that much to do, and it’s that exciting.”

Correspondent Simon Montlake contributed to this article.

Editor’s note: For more articles about the environment, visit the Monitor’s main environment page, which offers information on many environment topics. Also, check out our Bright Green blog archive and our RSS feed.

Previous

1 | 2 | 3