Soil Carbon Can’t Fix Climate Change by Itself—but It Needs to Be Part of the Solution

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Author: Marcia Delonge  26, 2016

A rigorous study just published in the prestigious journal Science argues that soil alone cannot be can be counted on to save us from climate change. Yet the stark analysis does not undermine the importance of better understanding, protecting, and building carbon in soils (“carbon farming”). In fact, the findings reinforce the need for soil carbon science and action to remain priorities, especially when it comes to agriculture.

The study in a nutshell:  Scientists from the University of California used 1-meter (3.28 ft) deep soil samples from 157 places around the world, which were analyzed with sophisticated carbon dating methods to improve the way that soil carbon is represented in some of the best Earth System Models. They found that models may have been overestimating how much carbon would likely be stored in soils under climate change, particularly in response to the so-called “CO2 fertilization effect” (the effect of higher atmospheric CO2 concentrations on fostering plant growth). The findings suggested that the size of the resulting soil carbon “sink” that will be available soon enough to effectively mitigate climate change is lower than previously estimated (by anywhere from 5.9% to 87%). They conclude that models need to represent soil carbon more accurately when simulating climate change scenarios, and emphasized the importance of emissions reduction strategies.

So what does this mean?

If you’re wondering about the implications of the study for soil carbon, climate change, and agriculture, here’s what you need to know:

  • As my colleagues have written, we are well beyond the stage where we can choose between either reducing emissions or increasing carbon sequestration. We need to act on both, and quickly.
  • To review the basics, there is a lot of carbon in the atmosphere (as CO2, the main climate change culprit today), but there is far more in soils. If you have been following “carbon farming”, you know that this feature of the carbon cycle is the basis for much enthusiasm. Since plants suck up CO2 and return carbon to the soil, there is constant movement between these two “pools.” Because the soil pool is large, small changes in soil carbon can mean relatively big changes in atmospheric carbon. This is great if soil carbon is increasing, but worrisome otherwise. Either way, understanding soil carbon is one of the keys to the climate change solution.

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