Amazon rainforest trees “living faster and dying younger” while absorbing less carbon

The most extensive land-based study of the Amazon to date reveals it is losing its capacity to absorb carbon from the atmosphere. From a peak of two billion tonnes of carbon dioxide each year in the 1990s, the net uptake by the forest has halved and is now for the first time being overtaken by fossil fuel emissions in Latin America.

The results of this monumental 30-year survey of the South American rainforest, which involved an international team of almost 100 researchers and led by the University of Leeds, were published last month in the journal Nature.

Measuring Amazon trees, Peru. Credit: Roel Brienen

Over recent decades the remaining Amazon forest has acted as a vast ‘carbon sink’ – absorbing more carbon from the atmosphere than it releases – helping to put a brake on the rate of climate change. But this new analysis of forest dynamics shows a huge surge in the rate of trees dying across the Amazon.

Lead author Dr Roel Brienen, from the School of Geography at the University of Leeds, said: “Tree mortality rates have increased by more than a third since the mid-1980s, and this is affecting the Amazon’s capacity to store carbon.”

Initially, an increase in carbon dioxide in the atmosphere – a key ingredient for photosynthesis – led to a growth spurt for the Amazon’s trees, the researchers say. But the extra carbon appears to have had unexpected consequences.

Study co-author Professor Oliver Phillips, also from the University’s School of Geography, said: “With time, the growth stimulation feeds through the system, causing trees to live faster, and so die younger.”

Recent droughts and unusually high temperatures in the Amazon may also be playing a role. Although the study finds that tree mortality increases began well before an intense drought in 2005, it also shows that drought has killed millions of additional trees.

RAINFOR team monitoring the Amazon canopy, Peru. Credit: Kuo-Jung Chao

Dr Brienen said: “Regardless of the causes behind the increase in tree mortality, this study shows that predictions of a continuing increase of carbon storage in tropical forests may be too optimistic.

“Climate change models that include vegetation responses assume that as long as carbon dioxide levels keep increasing, then the Amazon will continue to accumulate carbon. Our study shows that this may not be the case and that tree mortality processes are critical in this system.”

The study involved almost 100 scientists, many working for decades across eight countries in South America. The work was coordinated by RAINFOR, a unique research network dedicated to monitoring the Amazonian forests.

To calculate changes in carbon storage they examined 321 forest plots across the Amazon’s six million square kilometres, identified and measured 200,000 trees, and recorded tree deaths as well as growth and new trees since the 1980s.

“All across the world even intact forests are changing”, added Professor Phillips. “Forests are doing us a huge favour, but we can’t rely on them to solve the carbon problem. Instead, deeper cuts in emissions will be required to stabilise our climate.”

Videos: http://www.rainfor.org/en/videos

A map of the plots in the Amazon where tree measurements were taken for the study. Credit: Georgia Pickavance, RAINFOR / GLC2

More information:
[1] The RAINFOR project website: http://www.rainfor.org/en

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NASA – A year in the life of Earth’s carbon dioxide

An ultra-high-resolution NASA computer model has given scientists a stunning new look at how carbon dioxide in the atmosphere travels around the globe.

Plumes of carbon dioxide in the simulation shift and swirl as winds disperse the greenhouse gas away from its sources, which are dominated by North American, European and East Asian centres.

The simulation also illustrates differences in carbon dioxide levels in the northern and southern hemispheres and distinct swings in global carbon dioxide concentrations as the growth cycle of plants and trees changes with the seasons.

The carbon dioxide visualisation was produced by a computer model called GEOS-5, created by scientists at NASA Goddard Space Flight Center’s Global Modeling and Assimilation Office.

United States carbon emissions to be cut by 30 percent

New carbon emission regulations in the U.S. could yield over $90 billion dollars in climate & health benefits, says Gina McCarthy, administrator of the Environmental Protection Agency.

The U.S. power sector must cut carbon dioxide emissions 30 percent by 2030 from 2005 levels according to new federal regulations unveiled last Monday. The new regulations highlight a number of ways states can lower their emissions to meet these targets. Methods include carbon cap-and-trade systems, increasing use of renewable energy, replacing coal with natural gas and increasing energy efficiency.

Read the Reuters article on the topic here: http://www.trust.org/item/20140602140642-eztu0/?source=fiOtherNews2

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