Ancient Amazon Trees

Some of the trees in the vast Amazon rainforest might have been alive when Columbus landed in the New World. And that could be bad news for Earth's climate.

Findings published in 2005 show that Amazon trees, long thought to be quick growing and short-lived, are in some cases hundreds of years old. The oldest were on the order of 1,000 years, and one Amazon Methuselah hit 1,400.

While there are older trees on Earth -- California redwoods might live 2,000 years or more -- the revelation of ancient trees in the Amazon is likely to add to the worries of climate scientists, said Susan Trumbore, a UC Irvine earth system science professor who wrote the study along with Brazilian colleagues.

It means many climate models designed to calculate how fast the planet is warming up might be wrong.

The main culprit in global warming is carbon dioxide gas, a major byproduct of industrial civilization. It is believed to trap heat in Earth's atmosphere.

One of the ways to slow down global warming is to bind up carbon dioxide in the bodies of trees and other vegetation, climate scientists say. If the Amazon trees grew quickly -- as most experts thought -- they could be relied upon to absorb carbon dioxide, slowing the rate of warming.

But large, old trees are not as good at sequestering carbon dioxide.

"The potential for those forests to take up (carbon dioxide) has been overestimated," Trumbore said.

Trumbore and her fellow researchers estimate that as many as half of the trees in the Amazon greater than 3.9 inches in diameter could be more than 300 years old.

The Amazon basin contains a full third of the Earth's land vegetation.

"The little trees we all ignore are really old," Trumbore said. "One tree that we found was 12 centimeters in diameter – about the size of a CD. The tree was nearly 800 years old."

Tropical trees do not have easily identifiable tree rings, so until recently statements about their age were mostly guesswork.

But Trumbore, who takes frequent trips to the Amazon as part of an international team of scientists, used a sophisticated instrument at UCI called a particle accelerator to determine the age of tree samples.

By blasting bits of carbon from the wood and analyzing the results, the accelerator can tell the proportion of carbon 14 in each sample. The more carbon 14 has decayed, the older the wood.

Repeated tests of the same samples confirmed the results.

"Nobody believed us," she said of the tiny, nearly 800-year-old tree. "We didn't believe it either. We measured it seven or eight times."

Brazil nut trees, one of the few species widely recognized, ranged from 800 to 1,000 years old, Trumbore said.

Some of the researchers followed loggers around the rainforest to get samples of trees they cut down.

The research was done not only to learn more about global warming but also to help conservationists in the Amazon determine which trees to harvest, Trumbore said.

"If you're going to sustainably cut trees, you want to figure out which ones are going to take 1,000 years to replace versus a few decades," Trumbore said.

http://www.ocregister.com/news/trees-amazon-carbon-1960397-trumbore-old