May 062013
 
Carbon Sequestration in land that is holistically managed

Carbon Sequestration in land that is holistically managed vs. land that is conventionally managed. Source: Holistic Resource Management by Allan Savory

I received an interesting E-mail over the weekend from someone in Sweden who had watched the Grazing Days video about intensive rotational grazing on Youtube and had the following question:

“Can intensive rotational grazing work as a carbon sink in cold and humid climates like Sweden and not “only” in dry climates like Allan Savory has proven without doubt?”

This was my response to the question:

Please note that I do not claim to be an expert on the subject matter. My understanding is based on things that I have read, heard, observed and reasoned, and I don’t know if any of it would stand up to scientific scrutiny. Having given you that disclaimer, my understanding of how carbon sequestration works using plants is that grasses play an important role – even in cold and humid climates.

There are three factors we need to consider in order to answer your question:
1) The part of the plant that will produce the carbon we are looking to sequester;
2) The role that humidity plays in the breaking down of carbon; and
3) The role that temperature plays in the breaking down of carbon.

I will walk through each of these factors below to come to my conclusion of why carbon sequestration in grasslands works even in cold and humid climates.

1) Which part of the plant will sequester carbon:
When grasses grow, they produce carbon-chains in two different places: in the foliage above the ground and in the roots below the soils surface. As far as I understand it, the carbon-chains in the foliage above the ground are quite unstable and break down (through digestion, or rotting) quite quickly, where the carbon-chains in the roots below the ground are very stable and take a long time to break down – and are a main source of energy to the microbiology in the soil that help with functions of water and nutrient transportation from the soil into the plants.

Many farmers I speak to believe that incorporating foliage organic matter into the soil helps build organic matter, but as far as I understand it this is a myth. Incorporating foliage into the soil, is like giving the soil a shot of white sugar, which releases a lot of energy very fast as it breaks down, as opposed to feeding the soil with root-based organic matter, which is acts like a complex carbohydrate like a piece of whole-grain bread and breaks down over longer periods of time.

What we learn from this is that the long-term build up of carbon in our soils is accomplished by continuous growth and re-growth of roots below the soil surface. Grasslands are an excellent environment for root growth and re-growth and thus are excellent at producing stable forms of carbon for our soil.

2) The role of humidity:
Carbon breaks down more readily in humid climates. Allan Savory has demonstrated this throughout his work and can be easily observed when we look at the decomposition of organic matter above the soil surface in humid climates (where it quickly rots- in a biological process) and compare it to the organic matter decomposition above the soil surface dry climates, (where it oxidizes slowly – in a chemical reaction). Organic matter breaks down much faster in humid climates in the presence of microbiology.

Healthy soils though, regardless of whether they are in dry or humid climates, break down organic matter biologically – in an environment where water present. Below the soil surface in a healthy pasture with very good soil cover, there is not a very large difference between a humid and a dry climate. Two factors that ensure that water is present in the soil for this biological decomposition are: good grass cover allows for rain water to infiltrate the soil slowly and good grass cover that protects the soil surface from direct sunlight. This ensures that the climate in the soil includes moisture to facilitate biological activity regardless of whether it is humid or dry above the soil.

What we learn from this is that the decomposition of carbon in our soils is not that different between humid and dry climates – as long as the soils being compared are protected by healthy grass-growth. Since carbon sequestration can happen in healthy soils in dry climates as Allan Savory has demonstrated, then we can reason it can also happen in humid climates.

3) The role of temperature:
Temperature would plays a role in determining the speed at which reactions take place. The same is true for the decomposition of carbon in the soil. The warmer the temperature, the faster the carbon will get broken down (either biologically or chemically). The colder the temperature, the slower the carbon will get broken down. From this we can reason that colder soils are more effective at storing carbon than soils in warmer climates.

Especially in places like Canada and Sweden where due to frost, all biological activity in our soils goes dormant for large parts of the year, we are able to build on and maintain soil carbon levels that are much higher than in soils that do not fall below 0 degrees Celsius at any point in the year. This is also demonstrated by the lower levels of carbon found in soils around the tropics when compared to the carbon levels in soils found in more temperate climates.

What we learn from this is that colder climates are in a better position to store carbon than warmer climates are.

Conclusion:

To answer your question – it is definitely possible to use intensive rotational grazing as a technique to sequester carbon in soils in more humid and cooler climates.

 Posted by at 11:24 am

Sorry, the comment form is closed at this time.