Why Grassland Capital X Measures Environmental Services Instead of Soil Carbon

Grassland Capital X is a proposed conservation exchange that buys and sells ecosystem service benefits. Services such as biodiversity, water quality, and soil health are measured, quantified, verified, and then offered to buyers through a free market exchange. The exchange helps form an “environmental partnership” between landowners producing the services and buyers wishing to help the environment through the purchase of the services. 

Soil Health indicators such as soil aggregate stability, bacteria to fungi ratios, soil organic matter and soil microbial respiration are measured as proxies for ecosystem services such as climate regulation, carbon storage and carbon sequestration.

To answer the question “why didn’t we just measure soil carbon?”, let’s look at the carbon cycle and the path of a carbon molecule.

It all starts with photosynthesis - the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar to be stored as glucose. In simple terms, the carbon molecule in carbon dioxide now transforms to become part of long chain sugars, which in turn are broken down through cellular respiration to provide energy that plant cells use to live and grow. 

The carbon molecule that started as carbon dioxide is now part of the above ground plant canopy and below ground roots. But it doesn’t end there, plant root exudates (organic and amino acids) are then used to influence the rhizosphere around the roots to inhibit harmful microbes and promote  the growth of a complex variety of species and microorganism existing in the soil. 

This carbon molecule can then be found in soil microbes such as bacteria, fungi, and methanotrophs that use methane as an energy source, as well as the grazing animal tissue. Methane not used by methanotrophs returns to the atmosphere where it breaks down into water and carbon dioxide, starting the whole process over again.

When a plant is stressed through grazing it does two things. 1) sacrifices root resources to regrow a new canopy, leaving carbon behind deep in the soil, and 2) makes the plant roots send out long chain carbon as sugars to attract and feed fungi. The fungi then exchange nutrients the plant roots are unable to extract from the soil in exchange for carbon sugars. 

Many soil carbon experts are challenged with where and how to measure carbon. Do you measure carbon in the root soil, or do you measure the plant and root material as well? Also, which chains of carbon do you measure and where in the soil or plant material do you find the carbon chains?

When taking your soil samples, the depth of your sample is important to consider. Some will measure carbon at the surface (top 15 cm). This top 15 cm has a significant but shallow surface of active and decaying plant material and microbes that are all part of the carbon cycle. If this is your preferred method, then the time of day also becomes an important part of your measurement protocol as soil microbes respire in the morning leaving a cloud of carbon dioxide at ground level which can reach three to four times higher levels than regular atmospheric carbon dioxide. Plant leaves can soak up most of the respired CO2.

You can also measure beyond 15cm at a soil depth where deep grass plant roots have left a pool of secure carbon. Measurements beyond 30 cm can be difficult to obtain depending on soil type and land use which significantly increases soil sampling costs.  

Soil scientists, buyers, sellers, and other stakeholders agree that a standardized way to measure carbon is needed for markets to function with credibility and transparency. However, scientists that have spent decades determining methods to measure soil carbon are still not always in agreement on best methods and soil sampling protocols.  Many soil carbon measurement protocols do not lend themselves to measuring a complex grassland ecosystem which provides higher soil carbon storage. The question remains- where in the carbon cycle do you measure, at what depth of soil, and at what time of day. A healthy carbon cycle is dynamic and complex.

Instead of weighing in on the best way to measure soil carbon, Grasslands Capital X advisors have recommended measuring the ecosystem services generated from grasslands and the carbon cycle. By measuring soil health, in combination with other co-benefits of a grassland system, marketplace buyers can secure the benefits of a functioning ecosystems built on a functioning carbon cycle.  

In the end, grassland managers will manage what is measured, and what we are measuring helps achieve a wholistic healthy grassland ecosystem.  This wholistic approach will be a win- win- win for society, buyers, and ranchers.

Written By: Norm Ward, Governor of Western Stock Growers Association

Interested in learning more about Grasslands Conservation X?