It has been long-established that the accumulation of carbon dioxide in the atmosphere is a driving force behind the change in Earth’s temperature that has been observed in the past few centuries. A feasible solution to rising global temperatures, however, has not been established, but scientists are getting close.
Researchers at the Oak Ridge National Laboratory in Tennessee recently conducted a study in which they found that plants may absorb more carbon dioxide from the atmosphere than previously thought. In fact, they claim that many widely-accepted climate models for future generations are not entirely accurate because of their underestimation of how much atmospheric carbon dioxide is soaked up by Earth’s plant life. The reason behind these miscalculations is the fact that most climate models do not account for the way carbon dioxide diffuses inside the mesophyll tissue of a plant’s leaf. This has caused models to misjudge the total intake of carbon dioxide by plants by as much as 16%.
Figure 1 shows the anatomy of a plant leaf, which is an essential component in the process of photosynthesis. The palisade mesophyll towards the epidermis of the leaf contains many chloroplasts that are tall and closely packed to absorb maximum light. The spongy mesophyll towards the center of the leaf also captures light, but mainly serves to produce glucose and oxygen. The cells in the spongy mesophyll are relatively spread out, which allows for the diffusion of more carbon dioxide within plants.
Environmental scientists are currently trying to determine whether this 16% discrepancy is enough to slow down climate change and give humans enough time to curb their greenhouse gas emissions. While most news coverage and commentary has optimistically suggested that it might, many prominent scientists brush the newfound study off as meaningless from a big-picture perspective. Of these scientists is Oak Ridge Laboratory’s own Lianhong Gu, who asserts that, “…it (the 16% discrepancy) would not reduce the urgency of reducing (carbon dioxide) emissions. The climate change associated with fossil fuel use is much bigger than the response of plants to carbon dioxide.” Gu supports this claim by citing that the extra carbon dioxide stored in plants will follow the carbon cycle and eventually return to the atmosphere when the extra biomass dies. Martin Heimann, director of biogeochemical systems research at Germany’s Max Planck Biogeochemistry Institute makes a similar criticism by stating that, “…for the atmospheric carbon dioxide, only the net (land and ocean) uptake matters. If the land uptake is increased by a certain fraction, the land carbon release through respiration (the decay of dead biomass) will also increase.” Earth would need to at least double its land vegetation to keep up with carbon dioxide emissions, researchers say.
“Regardless of how much CO2 they soak up,” Gu says, “wild plants are a key ally in our quest to make civilization sustainable.” Scientists should concentrate their efforts on protecting plants rather than relying on them to protect the Earth. While it might not save the planet from global warming, Earth’s plant life will certainly soften the blow of climate change and provides many other ecosystem-related services beyond absorbing carbon dioxide. These services include the release of atmosphere cooling aerosols, the removal of toxic fumes from the air, and the production of life-saving medicines.