Trees have ‘more power’ to fight climate change20 December 2019
Tropical forests may have even more power to absorb carbon dioxide than previously calculated, reinforcing the need to save trees to fight climate change, a new study has found.
Scientists at the University of Reading used computer models to calculate how much light reaches leaves at various heights on trees in dense forests, to gauge their ability to remove carbon dioxide from the atmosphere through photosynthesis.
They found more light is reaching leaves lower down in the canopy than is currently factored into climate models, due to an over-simplification of the structure of trees. This means the world’s forests are taking up more CO2 than is currently recognised, making them even more important in efforts to offset carbon emissions.
The team estimated that the Amazon rainforest may be photosynthesising up to 10% more carbon than previously thought.
Dr Tristan Quaife, Associate Professor of Carbon Cycle Science at the University of Reading, said: “Climate models typically assume that leaves on trees are randomly distributed throughout the forest canopy. A consequence of this assumption is that leaves at the top of the canopy absorb more light than they should.
“By making trees more realistic in climate models by varying their structure, we found light actually reaches a lot further down into the forest, allowing more light to be absorbed by a large number of additional leaves.
“This means the power of forests, like the Amazon rainforest, to offset carbon emissions is likely being underestimated at the moment. This has implications for our understanding of the future impacts of climate change and action we take to manage them.”
The study, published in the journal Global Biogeochemical Cycles, was carried out with scientists at the University of Toronto. Renato Braghiere, the Reading PhD student who led the study is now a researcher at NASA’s Jet Propulsion Laboratory.
The team used satellite images to make trees more realistic in climate models, and then ran simulations to see what difference this would make to amount of carbon dioxide they absorbed globally.
Dr Quaife said: “It is important to add that photosynthesis is only half the story when it comes to trees storing carbon, and it is unlikely they would keep hold of all this extra carbon once other factors are considered.
“Nevertheless, this research helps show how important tropical rainforests are to the planet. Models need to factor in the structural variability of trees if we want an accurate picture of our future climate. This is particularly important as we model the effects of planting more trees, or preventing the destruction of existing forests, as techniques to prevent future climate change.”