According to an international group of scientists led by Dr Nate Stephenson of the US Geological Survey, most of tropical and temperate tree species grow more quickly and sequester more carbon as they grow older.
Eucalyptus bridgesiana tree.
The report, published in the journal Nature, is based on repeated measurements of 673,046 individual trees belonging to 403 species, some going back more than 80 years.
“Rather than slowing down or ceasing growth and carbon uptake, as we previously assumed, most of the oldest trees in forests around the world actually grow faster, taking up more carbon. A large tree may put on weight equivalent to an entire small tree in a year,” said co-author Dr Richard Condit from the Smithsonian Tropical Research Institute.
“This report would not have been possible without long-term records of individual tree growth. It was remarkable how we were able to examine this question on a global level, thanks to the sustained efforts of many programs and individuals,” added co-author Dr Mark Harmon of Oregon State University.
“Extraordinary growth of some species, such as Australian mountain ash – also known as eucalyptus – (Eucalyptus regnans), and the coast redwood (Sequoia sempervirens) is not limited to a few species,” Dr Stephenson said.
“Rather, rapid growth in giant trees is the global norm and can exceed 600 kg per year in the largest individuals. In human terms, it is as if our growth just keeps accelerating after adolescence, instead of slowing down. By that measure, humans could weigh half a ton by middle age, and well over a ton at retirement.”
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