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Increasing CO2 levels is not going to benefit grasslands as much as previously believed

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Posted February 25, 2019

Rising levels of carbon dioxide will cause havoc on our climate. However, plants consume CO2 and flourish by doing so. Scientists have long assumed that rising CO2 levels will actually increase grasslands that are already covering around 33 % of Earth’s land. However, a new research from the University of Tasmania has shown that this is not going to happen.

Grasslands should enjoy the increase of the atmospheric CO2, but in actual reality rain becomes the limiting factor. Image credit: J Brew via Wikimedia (CC BY-SA 2.0)

CO2 will make the grass greener – this bizarre-sounding idea was actually considered to be a scientific fact. Green plants consume CO2 in order to produce energy that they need to grow. At the same time they produce oxygen that we breathe. In other words, the more plants we have, the more clean air we have to breathe.

However, a new research showed that for this to work grasslands would have to receive more rain at the right time. Also, the amount of rain should be substantial to fuel that increase in growth. And scientists say that this is not going to happen.

Previously scientists have calculated that grasslands are likely to get a 20 % boost thanks to fertilizing effects of CO2. However, a more recent study says that this factor could be closer to 6 % rather than 20 and it has everything to do with rain.

Scientists analysed results of 19 different experiments on the effect of carbon dioxide and precipitation on grasslands in Tasmania and Denmark and found that growth is stimulated more in sites that have most of their rain in spring. In other words, for the increase of CO2 to have a positive effect on grasslands, rain has to occur on correct time and in a correct amount. Scientists determined that natural rain cycle is going to be the most significant limiting factor for the growth stimulated by the atmospheric CO2. Furthermore, if most of the rain falls out during other times rather than spring, it may have an opposite effect.

Team of researchers have been puzzling over a fact that grasslands are not flourishing in different places at the same rate despite CO2 effect being largely the same. The time of rain may provide an explanation to that phenomenon.

Mark Hovenden, lead author of the study, said: “Importantly, these results are from actual experiments distributed across the world and show that the response is uniform across all grasslands, despite large differences in climate and local conditions. Therefore, this is something fundamental about the way this system will respond to the rising CO2 concentration”.

Rain is not a simple subject when climate change is discussed. The entire weather pattern is going to take a hit from the climate change. Scientists are convinced that extreme weather events are going to be more and more frequent. And that could mean more irregular droughts and irregular rain seasons.

 

Source: University of Tasmania

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