Some Amazon rainforest trees are over 1000 years old finds study
Rhett A. Butler, mongabay.com
December 13, 2005
Trees in the Amazon rainforest are older than originally believed according to new research published in the Proceedings of the National Academy of Sciences. A team of American and Brazilian researchers using radiocarbon dating methods to study tree growth in the world’s largest tropical rainforest found that up to half of all trees greater than 10 centimeters in diameter are more than 300 years old. Some of the trees are 750 to 1,000 years old says Susan Trumbore, a professor of Earth system science at University of California at Irvine and one of the authors of the study.
“Little was known about the age of tropical trees, because they do not have easily identified annual growth rings,” said Trumbore in a media statement. “No one had thought these tropical trees could be so old, or that they grow so slowly.”
According to Trumbore, the finding may have important implications for the role the Amazon plays in determining atmospheric carbon dioxide concentrations. Because Amazon forest trees are old and slow-growing says the researcher, they have less capacity to absorb atmospheric carbon than previous studies have predicted.
“In the Central Amazon, where we found the slowest growing trees, the rates of carbon uptake are roughly half what is predicted by current global carbon cycle models,” Trumbore said. “As a result, those models — which are used by scientists to understand how carbon flows through the Earth system — may be overestimating the forests’ capacity to remove carbon dioxide from the atmosphere.”
The growth rates measured by the team for trees in the Central Amazon are among the slowest in any forest on Earth. Trumbore says slow growth is likely due to the nutrient-poor soils of the Central Amazon combined with the low light conditions created by the shade of the forest canopy.
The slow-growing nature of Amazon trees may also mean that it takes longer for forests to recovery from logging.
Strangler fig tree in the Amazon.
Deforestation in the Amazon rainforest fell 37% for the 2004-2004 year according to Brazilian government figures released today. Between July 2004 and August 2005, 7,298 square miles of rainforest (18,900 square kilometers) — an area almost half the size of Switzerland — were destroyed. Last year the figure was 10,088 square miles (26,129 sq km kilometers) and since 1978 some 206,250 square miles (534,200 sq km) of forest has been lost.
The biodiversity of the Amazon rainforest results from biological factors, not climate change as widely thought, says new research published in the journal Proceedings of the Royal Society B. Scientists have long argued that the species richness of tropical forests could be due to climate change-induced fragmentation, known as the “forest refuge: theory, and other external factors that caused geographic isolation. Now, researchers from University College London say that biological influences play a greater role in driving species evolution.
Controversial evidence uncovered over the past decade suggests that the Amazon rainforest was once home to large sedentary populations of people. Besides the well-known empires of the Inca and their predecessors, the Huari, millions of people once lived in the forests and shaped the environment to suit their own needs. The Amazon has a long history of human settlement. Contrary to popular belief, sizeable and sedentary societies of great complexity existed in the rainforests of this region. These societies produced pottery, cleared sections of rainforest for agriculture and managed forests to optimize the distribution of useful species. The notion of a virgin Amazon is largely the result of the population crash following the arrival of the Europeans in the sixteenth century.
“The impact of logging activity in the Amazon region may be longer-lasting than we think,” Trumbore added, “because it may take centuries for these forests to grow back to their full size.”
The long recovery time after logging is a particular concern after a study released by the Carnegie Institution found that “selective logging” is degrading Brazil’s Amazon rain forest twice as fast as deforestation figures suggest. Using remote-sensing technology, the Carnegie Institution team determined that conventional analysis missed much of the degradation that occurs beneath the rainforest’s protective canopy.
The new research was conducted as part of the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA). Supported by NASA, the LBA is a Brazilian-led international scientific program with the goal of studying how the Amazon forest affects global climate and carbon dioxide. This specific study was a cooperative effort among researchers at the University of Sao Paulo, University of Acre and the Institute for Amazonian Research in Brazil, and UCI and Tulane University in the U.S. Radiocarbon measurements were made at the W.M. Keck Carbon Cycle Accelerator Mass Spectrometry Facility at UCI.
Recent articles on carbon sequestration and forests
Deforestation causes 25% of greenhouse gas emissions 12/09/2005
Yesterday the Food and Agriculture Organization of the United Nations (FAO) offered to provide forestry data and technical assistance to countries looking to mitigate greenhouse gas emissions through the reduction of forest loss.
Future forests may absorb more carbon dioxide than current forests 12/07/2005
Forests of the future may grow faster and absorb more carbon in a carbon dioxide enriched environment according to a new study by researchers at the Department of Energy (DOE).
Temperate forests may worsen global warming, tropical forests fight higher temperatures | 12/05/2005
Growing a forest might sound like a good idea to combat global warming, since trees draw carbon dioxide from the air and release cool water from their leaves. But they also absorb sunlight, warming the air in the process. According to a new study from the Carnegie Institution’s Department of Global Ecology and Lawrence Livermore National Laboratory, planting forests at certain latitudes could make the Earth warmer.
70 years after logging, forests don’t hold as much carbon as original forests | 12/05/2005
New research out of Ohio State University suggests that following logging, temperate forests take long periods of time to recover their carbon storing capacity. The scientists examined forests of of the upper Great Lakes region, which were 90% logged at the turn of the century, and found that they store only half the carbon the original forests contained. Poor forest management is blamed for the shortfall.
Elevated atmospheric CO2 increases soil carbon | 12/05/2005
An article in the current issue of Global Change Biology indicates that soils in temperate ecosystems might contribute more to partially offsetting the effects of rising atmospheric CO2 concentrations than earlier studies have suggested.
Vegetation growth in Arctic could add to global warming | 9/8/05
Warming in the Arctic is stimulating the growth of vegetation and could affect the delicate energy balance there, causing an additional climate warming of several degrees over the next few decades. A new study indicates that as the number of dark-colored shrubs in the otherwise stark Arctic tundra rises, the amount of solar energy absorbed could increase winter heating by up to 70 percent. The research will be published 7 September in the first issue of the Journal of Geophysical Research-Biogeosciences, published by the American Geophysical Union.
This article used information from a news release from the University of California, Irvine.