Sink It or Lose It: The Carbon Trade-off
Author: Rolf Sommer | Published: March 20, 2017
In the race to keep climate change in check, our soils are an important ally. A natural carbon sponge, they represent the earth’s largest terrestrial store of this essential, life-giving element.
And if we’re to meet the climate targets laid out in the Paris Agreement, then we must take advantage of the ability to sink carbon in soil, especially because this can offset harmful greenhouse gas emissions elsewhere.
But while we’re at the forefront of understanding how to make the most of soils to remove carbon dioxide from the atmosphere, our research shows that we’ve still got a way to go before we can realize the full potential of long-term carbon storage – or carbon sequestration.
Before anything else, we need to be realistic about how much carbon our soils actually can store, how long this will take, how this changes from region to region, and how much this would contribute to climate change mitigation.
Evidence is improving and research advancing, but we still don’t have enough data. Not surprisingly, many aspirations are based on quite a bit of guesswork.
At the International Center for Tropical Agriculture (CIAT), we have found that even using the best soil management techniques known to science, we can’t seem to store enough carbon – if any – to put a notable dent in global emission figures.
Yet what we do know is that carbon is being lost from soils, especially in the humid tropics, where there is a high turnover of the organic matter in which carbon is found. So we need to focus on reducing – and avoiding – carbon losses before we talk about carbon storage, or sequestration.
One of the contributors to carbon loss is tilling the soil, a common activity on most smallholder farms in developing countries. Here, only very small amounts of organic matter – from crop residues, manure or compost – are dug back into the soil, as these resources are usually in short supply.
It’s a tall order to call on African smallholders to mitigate greenhouse gas emissions and build carbon in the soil when food insecurity, drought and other challenges are looming. For them, harvesting food – to eat or sell – is the number one priority. And, these farmers already contribute very few emissions to start with, paling in comparison with large commercial farms.
But our research shows that little changes could have tremendous impacts. For instance, quantifying the climate smartness of best soil protection and restoration practices in Kenya, Ethiopia, Burkina Faso, India and Benin revealed that there are methods that can sustainably intensify farming systems without adding to greenhouse gas emissions.
If we can convince farmers to adopt small soil conservation practices, we can slow carbon loss down significantly, quickly and without too much effort. The bottom line is that we need more sophisticated management practices than the ones being advocated right now, since sustainable and smart cropping systems have not yet been widely adopted.