Trees can absorb less carbon dioxide from the atmosphere than previously thought, new study finds
A new study shows that mature forests can absorb much less carbon dioxide than previously thought, suggesting that Earth may be closer to a climate change tipping point than previous models did. had suggested.
A team of researchers from the University of Western Sydney, led by Professor Belinda Medlyn, spent four years measuring the carbon dioxide uptake rates of 90-year-old eucalyptus trees in a wooded area near Sydney.
Current models of climate change estimate that mature trees should absorb about 12 percent of carbon dioxide from the atmosphere and sequester it so that it does not re-enter the ecosystem and contribute to warming.
A team of scientists from the University of Western Sydney spent four years pumping carbon dioxide into a mature eucalyptus forest in Australia to measure how much CO2 the trees could absorb.
To test the hold of this estimate, Medlyn and her team built a hanging ring of tubes above the forest and pumped carbon dioxide into the forest below.
Carbon dioxide levels were about 38 percent higher than current levels, and trees initially absorbed the expected 12 percent of carbon dioxide.
What was surprising, however, was that the trees weren’t able to sequester the carbon dioxide they had absorbed to keep it from re-entering the atmosphere.
“ Just as we expected, the trees absorbed about 12% more carbon under enriched CO2 conditions, ” Medlyn said. Eurekalert.
‘However, the trees did not grow any faster, which begged the question:’ Where has the carbon gone? ”
Typically, plants and trees absorb carbon dioxide as part of the photosynthetic process, which stimulates growth.
But instead of growing, the mature eucalyptus just seemed to circulate carbon dioxide through the environment before it was finally reintroduced into the atmosphere.
“Trees convert the absorbed carbon into sugars, but they can’t use those sugars to grow more because they don’t have access to additional nutrients from the soil,” Medlyn said.
“Instead, they send the sugars underground where they ‘feed’ the soil microbes.”
Although the trees were able to absorb about 12 percent of the CO2, as expected, they were not able to retain the CO2 by sequestration. Eventually, all the CO2 absorbed by the trees was reintroduced into the atmosphere through the soil or the trees themselves.
According to the team, the trees transmitted about half of the carbon dioxide absorbed into the soil, where it was processed, and then released into the atmosphere by soil bacteria or small fungi on the forest floor.
The other half of the carbon dioxide was simply released by the trees themselves.
One possible explanation for this could be the relatively poor health of the soil itself.
“It doesn’t contain a lot of nutrients,” Medlyn said.
“Plants need these nutrients to grow, so it seems what they’ve done when given extra carbon is just use it to look for additional nutrients.
The results suggest that current climate models that assume mature forests will be able to sequester CO2 at a steady, perhaps overly optimistic rate.
Current models of climate change have set a maximum warming target of 2.7 degrees Fahrenheit above the Earth’s pre-industrial average global temperature.
If mature forests have less capacity to absorb carbon dioxide than these models took into account, our calculations for staying below this warming target could be wrong.
“ For now, these global calculations assume that mature forests will store additional CO2 as concentrations increase, but our results imply that mature forests may not continue to do so in the future, ” Medlyn said. in a separate interview with ABC News.
THE MAP REVEALS THE DEVASTATIVE RATE OF DEFORESTATION IN THE WORLD
Using Landsat imagery and cloud computing, the researchers mapped forest cover around the world as well as forest loss and gain. In 12 years, 888,000 square miles (2.3 million square kilometers) of forest have been lost and 309,000 square miles (800,000 square kilometers) have regained
The destruction caused by deforestation, forest fires and storms on our planet has been revealed in unprecedented detail.
High-resolution maps released by Google show how the world’s forests suffered an overall loss of 1.5 million km2 between 2000 and 2012.
By comparison, this is a loss of woodland equal in size to the entire state of Alaska.
The maps, created by a team involving NASA, Google and researchers at the University of Maryland, used imagery from the Landsat satellite.
Each pixel in a Landsat image shows an area the size of a baseball diamond, providing enough data to zoom into a local region.
Previously, country-to-country comparisons of forest data were not possible at this level of precision.
“When you put together datasets using different methods and definitions, it’s hard to synthesize them,” said Matthew Hansen of the University of Maryland.