Plants – the natural superhero combating climate change

 

Plants have this special ability that helps us combat climate change. But this special ability is nothing unusual to plants at all. It’s called photosynthesis.

 

Plants take up CO2 from the atmosphere and keep concentrations low. Taken by D Coetzee on Flickr.

 

Carbon dioxide (CO2) concentrations in the atmosphere increase sharply every year. However, plants have limited this increase from the start of the Industrial Era. But how does it actually do this?

 

Photosynthesis is our natural superhero

Plants take up CO2 from the atmosphere to carry out photosynthesis, which has offset a significant amount of concentrations from the atmosphere. Climate scientists have determined that the absorption of CO2 by plants (and by the ocean) has meant that only about 40-45% of emissions remain in the atmosphere every year. So without plants, concentrations may have reached levels today that would be close to unbearable for humans to live in. How about that for saving the planet thus far?!

 

But there’s something trying to stop the superhero

There’s evidence to suggest that climate change is actually eating away this ability that plants have. Rising temperatures might be reducing the supply of water available to plants around the globe. This could be bad for plants because, as well as CO2 in the atmosphere, they also need water vapour in the air to photosynthesise.

A recent study by Prof Wenping Yuan (Yuan et al., 2019) considered how increasing temperatures are changing the available supply of water vapour in the air and how much they require. In warmer environments, plants need to absorb more water vapour to account for the increased dehydration. Normally, this would be fine, since the air can also hold more water vapour when temperatures increase. However, Yuan’s study revealed that the amount of water in the air has actually changed little to none throughout the globe in the last 20 years.

This induces a deficit of available water to plants and in turn halts their ability to photosynthesise. As a result, plants might be less able to harness their “super” abilities to limit climate change in the future.

 

“The two opposing effects…”

So while photosynthesis enables plants to take up CO2 from the atmosphere, the rise in temperatures tries to halt it. These two “effects” on the amount of CO2 can be separated like an ultimate battle between the superhero and its enemy.

The superhero takes up CO2 from the atmosphere. Plus, the more CO2 is in the atmosphere, the more is taken up by plants. So the superhero gets stronger as CO2 concentrations rise, limiting its increase.

The enemy halts photosynthesis and therefore the amount of CO2 taken up by plants. The enemy also gets stronger as CO2 concentrations rise, which offsets more CO2 being taken up by plants and leaves even more of it in the atmosphere, causing a scary feedback loop.

 

So who’s winning the fight?

The rate at which photosynthesis is increasing or decreasing throughout the globe depends on who is winning the battle. Right now, the superhero is clearly outweighing the enemy’s fight back, which means that photosynthesis is currently growing overall. This is good news in regards to climate change so far. But scientists are questioning whether photosynthesis will continue to lead the fight in the future. The effect of increasing temperatures is amplifying the deficit of water for plants, which is limiting the growth of photosynthesis more and more every day.

If the power of the enemy continues, it might just take over one day. Photosynthesis throughout the globe will decrease and CO2 concentrations will increase much faster than they do today.

That would be very bad news in regards to climate change and is referred by climate scientists as the ‘runaway effect.’ This very possibility is unprecedentedly scary and quite unusual, even for plants.

 

Reference:

Yuan, W., W., Zheng, Y., Piao, S., Ciais, P., Lombardozzi, D., Wang, Y., Ryu, Y., Chen, G., Dong,
D., Hu, Z., Jain, A., K., Jiang, C., Kato, E., Li,  S., Lienert, S., Liu, S., Nabel, J., Qin, Z.,
Quine, T., Sitch, S., Smith, W., K., Wang, F., Wu, C., Xiao, Z., Yang, S. (2019). Increased
atmospheric vapor pressure deficit reduces global vegetation growth. Science
Advances, 5(8), 1-12, doi: 10.1126/sciadv.aax1396


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