Trees might become CO2 sources by 2050
Approximately 30% of our carbon dioxide (CO2) emissions are absorbed by the remaining forests and land ecosystems. However, new studies are showing that the increasing global temperatures might transform these natural “sinks” into carbon “sources”.
To better understand why this might happen, let’s quickly understand how plants work. There are two chemical processes that plants undergo for survival: photosynthesis and respiration. During photosynthesis, plants absorb CO2 and sunlight through their leaves to eventually produce sugar and oxygen (which gets released into the atmosphere). This only happens when sunlight is available. Alternatively, plants use respiration to transfer the produced energy to their cells. Like humans, the waste product that is excreted by this process is CO2.
An interesting observation was made by Duffy and her team members who analyzed records of CO2 movement from 1991-2015 from a global observation network called FLUXNET. They found that, depending on the species of plant, global photosynthesis peaked during certain temperatures only to decline thereafter. In contrast, global respiration rates across all ecosystems increased with no specific maximum threshold. The study showed that at elevated temperatures, respiration rates increased whereas the rate of photosynthesis sharply decreased.
This is not good news for us. This could mean that plants’ potential to absorb CO2 might drop by 50% by 2040! In other words, trees and plants will no longer be considered as carbon sinks. Rather, they’ll start behaving as carbon sources. To make matters worse, most of the carbon pledges made in the Paris Agreement heavily depend on land uptake on carbon.
The bad news is that Earth is currently expected to heat up another 2-3 degrees by the end of the century. The good news is that we still have the ability to drastically reduce our emissions to halt further global temperature increases and prevent forests from flipping from CO2 sinks into sources.
