A team of US, Dutch and Australian scientists have published a paper that estimates the global rate of photosynthesis, the chemical process that governs how ocean and land plants absorb and release carbon dioxide. 

 

The new findings show that plants absorb carbon dioxide (CO2) up to 25 per cent faster than previously believed.

 

The team analysed more than 30 years of data collected by the Scripps Institution of Oceanography and air samples collected by the CSIRO and Bureau of Meteorology from the Cape Grim Air Pollution Monitoring Station. Scientists deduced the rate of photosynthesis over several decades as well as identifying the El Nino-Southern Oscillation phenomenon as a regulator of the type of oxygen atoms found in C02.

 

"Our analysis suggests that current estimates of global primary production are too low and the refinements we propose represent a new benchmark for models to simulate carbon cycling through plants," says co-author, Dr Colin Allison, an atmospheric chemist at CSIRO's Aspendale laboratories.

 

The research team, led by Dr Lisa Welp from the Scripps Institution of Oceanography, traced a path of oxygen atoms in C02 molecules, which showed the team how long the carbon dioxide had been in the atmosphere and how long it had taken for it to pass through plants. This method showed the team that carbon dioxide took 25 per cent less time for the plant to process than previously thought.

 

"It's difficult to measure the rate of photosynthesis for forests, let alone the entire globe. For a single leaf it’s straightforward, you just put it in an instrument chamber and measure the CO2 decreasing in the chamber air," said Dr Welp.

 

"But you cannot do that for an entire forest. What we have done is to use a naturally occurring marker, an oxygen isotope, in atmospheric CO2 that allows us to track how often it ended up inside a plant leaf, and from oxygen isotopic CO2 data collected around the world we can estimate the mean global rate of photosynthesis over the last few decades."

 

The authors of the paper said that the revised understanding of photosynthesis would help guide future estimates of plant activity, such as the capacity of forests and crops to act as bulwark against climate change.

 

Dr Allison said that better understanding of the exchange of gasses – particularly of C02 – is especially significant to climate science and to policymakers.

 

"Quantifying this global production, centred on the exchange of growth-promoting CO2 and water vapour, has been historically difficult because there are no direct measurements at scales greater than leaf levels,” Dr Allison said.

 

"Inferences drawn from atmospheric measurements provide an estimate of ecosystem exchanges and satellite-based observations can be used to estimate overall primary production, but as a result of this new research we have re-defined the rate of biospheric carbon exchange between atmosphere, land and ocean.