Most extensive study of the Amazon to date reveals startling early death of rainforest trees.
Life expectancy of Amazon trees has declined by more than a third since the mid-1980’s.
Imagine the concern we’d have if our emissions cut short our lifespans so that no one lived to the age of 50!
The Amazon forest, largest rainforest on Earth, acts as a vast ‘carbon sink’ – absorbing more carbon (CO2) from the atmosphere than it releases. The simple-minded thinking has been that this has been helping to put a brake on the rate of climate change brought on by the sudden dumping of nearly a trillion tonnes of fossil CO2 into the air in the past century. Indeed a new long-term 30 year study of the Amazon forest shows a huge surge in the growth rate of the Amazon trees and shockingly also devastating decreased tree life expectancy. The trees are living fast dying young!
While this scientific opus focused on Amazon trees the same life shortening effects of high and rising CO2 is cutting trees down in the prime of life all over the world.
One immediate consequence of the trees dying young is that the net amount of CO2 the forest takes in vs. emits has declined sharply. 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 regional fossil fuel emissions.
Lead author Dr Roel Brienen, 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.”
This is truly terrible news as trees in the Amazon ordinarily live to incredible age. We know from a similarly surprising study published in 2005 that half of the trees in the Amazon that are more than a tiny 4 inches in diameter are over 300 years old, many more than 1000 years old. Those small trees on the right side of the photo at the top of this page are likely centuries old. By comparison a 4 inch (10cm) diameter tree in North America or Europe is typically less than 20 years of age! The rainforest trees normally grow very very slowly and steadily for centuries. So with the news that our high and rising CO2 has cut their lifespans by a third that means we have taken 100 years or more of prime growth years away from hundreds of billions of vital trees, often referred to as the lungs of the planet. Yikes, talk about the deadly effects of our second-hand smoke.
In our human context, we have an average lifespan of about 72 years, if our lives were cut short by a similar third to age 47 the human family would be in dire and desperate shape. Keep in mind there are 40 times more trees living in the Amazon than there are humans on all of the earth.
Here’s a wonderful short music vid about the wonder of ancient trees.
To read more about the Bristlecone Pine here’s my post about having lunch one day long ago sitting at the foot of and with perhaps the oldest living thing of earth
Largest rainforest on Earth speeding to its death from fossil fuels second-hand smoke
The dramatic increase in carbon dioxide in the worlds atmosphere tied to fossil fuel burning. CO2 is the key ingredient for plant photosynthesis and extra CO2 is proven to lead to accelerating growth for the Amazon’s trees. Indeed this high and rising CO2 has produced a dramatic Global Greening across the planet in all ecosystems. The CO2 stimulated growth spurt in the Amazon is now shown to have not simple good effects but dire consequences that are certain to become worse in coming decades.
At 6 million km2, the Amazon forest has an area 25 times as great as the United Kingdom (or 15 times the size of California). It spans nine countries including Bolivia, Ecuador, Colombia, Peru, Venezuela, French Guyana, Guyana, and Suriname. Its three hundred billion trees, in 15,000 species, store one fifth of all carbon in the Earth’s terrestrial biomass. Each year Amazon forests cycles 18 billion tons of CO2 within its standing biomass.
CO2 and Dust
In addition to the CO2 greening effect the Amazon is also experiencing an increase in vital nutrient laden dust that is blowing from the Sahara. This Saharan dust is vital in sustaining Amazon forest growth and has been seen to be increasing over the time frame of the study. Such increased CO2 and dust is known to impact rainfall regimes and bring on droughts so there is nasty feedback loop engaged.
Co-author Professor Oliver Phillips said: “With time, the growth stimulation feeds through the system, causing trees to live faster, and so die younger.”
Recent mega-droughts and accompanying unusually high temperatures in the Amazon are synergistically playing an additional harmful 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. The faster growing ‘rebel without a cause’ trees have less extensive root systems which means they are less drought resistant and more vulnerable.
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 will have to be revised
Climate change models that include vegetation responses assume that as long as carbon dioxide levels keep increasing, then the Amazon trees will continue to more efficiently take in much of that extra carbon. The study shows that this may not be the whole story and that younger tree mortality is likely critical to the sustainable growth and health of the forest.
To calculate changes in carbon storage they repeatedly examined over the years 321 long term 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.”
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.