Climate scientists have found that increasing levels of carbon dioxide in the atmosphere have led to a global increase in the rate of photosynthesis since the early 2000s. The results were recently published in the Proceedings of the National Academy of Sciences.
Plants produce energy through photosynthesis, absorbing carbon dioxide from the atmosphere or water, a process known as primary production. This process speeds up as the gas concentration increases. This phenomenon is called the carbon dioxide fertilization effect.
Now, Chi Chen and colleagues at the University of California, Berkeley, have quantified the effects of carbon dioxide fertilization on land plants worldwide. The team collected data from 68 locations around the world — including crop fields, grasslands and forests — to measure changes in the concentration of carbon dioxide in the air directly above the plants between 2001 and 2014.
At these sites, the rate of photosynthesis has increased, absorbing an extra 9.1 grams of carbon per square meter per year since 2001. The team calculated that about 44% of the increase was attributable to rising carbon dioxide levels in the atmosphere, while 28% was attributable to rising temperatures. The team then combined data from these locations with satellite data and global vegetation models to estimate changes over time on a global scale. They found that primary production of plants has increased globally – since 2001, plants have absorbed an extra 4.4 grams of carbon per square meter per year.
Differences in CO2 fertilization effects at these sites and globally are due to uneven distribution of plants across the globe, as well as differences in the productivity of vegetated regions.
The total surface area of leaves around the world has increased in recent decades. “This is largely due to the fertilizing effect of carbon dioxide,” Chen said.
“It has been observed that plants use water more efficiently in the presence of elevated carbon dioxide concentrations, which often results in faster plant growth because water is often a limiting resource.” “They may also grow faster and take in more carbon, although other factors, such as nutrition, may limit the amount of photosynthesis that growth translates into growth,” said Trevor Keenan.
However, the negative effects of climate change may eventually offset the carbon dioxide fertilization effects mentioned in the study. For example, more frequent and severe droughts caused by climate change are having a detrimental impact on plants around the world, resulting in more frequent forest fires and insect infestations, Keenan said.
“While plants have bought us time by absorbing more carbon dioxide in response to the increased carbon dioxide in the atmosphere, that’s not enough to stop climate change,” Keenan said. “Reducing emissions is the only way to stop continued warming in the future.”