There is a trope In the climate denial world, that rising carbon dioxide level is actually good, because it helps plants grow. Aside from that saying that ignores all harmful effects on life on Earth, there is another problem with the tired talking point.
A new study published in Nature on Wednesday suggests that while atmospheric carbon dioxide concentrations are increasing can stimulate plant growth, it takes a huge toll on another major source of carbon sequestration that only those plants and trees lie: the ground.
Dirt is an essential part of the carbon cycle, but the impact of rising carbon dioxide on the soil is a notable gap in the literature. The authors of the new study decided to fill that gap. The study notes that there is a generally accepted assumption that the carbon content in the soil will increase as plants capture more carbon, because when those plants die, they decompose and turn into soil. But there isn’t much evidence to support that.
“As a scientist, I was amazed at how little we knew about the effects of [estimated concentrations of carbon dioxide] about soil carbon stocks compared to plant properties, ”Cesar Terrer, a fellow at the Lawrence Livermore National Lab and a Stanford University postdoctoral fellow who worked on the study, wrote in an email.
For the study, Terrer and colleagues analyzed data from 108 previously published papers focusing on soil carbon levels and plant growth amid increasing carbon concentrations. They found that when the carbon content increases, the organic matter in the soil also increases. But contrary to what conventional wisdom would lead them to believe, the researchers found that an increase in soil biomass usually coincided with a decrease in soil carbon content.
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“We expected faster plant growth and more biomass to increase soil organic carbon as additional leaves and biomass fall to the forest floor,” wrote Rob Jackson, professor of Earth systems science at Stanford University and the study’s senior author, in a statement. e-mail. “That didn’t happen, and that was the biggest surprise in our work.”
In fact, the authors found that the soil only accumulated more carbon in experiments where, although the atmosphere had high carbon concentrations, plant growth continued at a steady rate rather than increasing rapidly.
The authors think they know why this is: As plants grow faster, they need more nutrients, which they get from the soil. Soil needs to be in order to give plants access to more nutrients grow microbes such as bacteria and fungi faster. That requires them to increase their rate of microbial respiration, releasing carbon into the atmosphere might have stayed differently in the earth.
Not all ecosystems, the authors write, will behave in the same way in this regard. Based on their meta-analysis, the authors fashionhow much carbon the soil of different landscapes will absorb as the carbon in the atmosphere increases. They found that if carbon dioxide concentrations reach double pre-industrial levels, carbon uptake from forest soils will remain flat, but grassland soils will increase by 8%. That’s probably the case because in grasslands, plants allocate more of their carbon to their roots, rather than above ground, and studies show that decomposing roots tend to put more carbon into the soil than other parts of plants. This suggests that world leaders should focus on recovery and conservation efforts on these ecosystems as a form of climate mitigation.
These findings are important implications for how climate scientists explain the amount of carbon that forests, grasslands and wetlands can store. Since existing climate projections do not take into account the trade-off between soil and plant carbon sequestration, they likely overestimate the potential of land to absorb carbon and reduce global warming. That means we may not have as much leeway with carbon pollution as we may have thought.
“Forests and other lands currently absorb a third of global carbon pollution, about 12 billion tons of carbon dioxide per year,” said Jackson.We need to understand whether this valuable service continues. “