Working Group:
Managing Soil Carbon

Any viable approach to achieving the UN’s Sustainable Development Goals (adopted in 2015) requires addressing soil, which is the foundation of both healthy natural and agricultural systems. However, reliable, quantitative data on the contributions of key soil properties – like soil organic matter – to achieving production and environmental goals are lacking, which makes it difficult, if not impossible, to successfully create science-based targets to manage soils to achieve targeted outcomes for nature and people.

Working Group Summary

Improving Science-Based Soil Management

Because soil organic matter (SOM) is considered a major arbiter of soil health and can be built up or broken down by land management, it is the most relevant target for human wellbeing and conservation interventions. However, despite wide acknowledgment of the importance of SOM, there are no reliable, quantitative targets for the amount of SOM required to achieve SDG-relevant impacts, such as carbon sequestration and nutrient reduction in waterways. The Managing Soil Carbon Working Group is working to improve science-based soil management by quantifying the relationships between: SOM and crop yield, livestock value, carbon storage, biodiversity outcomes, and nutrient retention. The group will use its findings to generate specific SOM-based targets to manage soils at test sites in California and the American Midwest.

The Challenge

Closing the Knowledge Gaps in Soil Management

Management of SOM can increase agricultural productivity, remove carbon from the atmosphere, and protect water systems from contamination. In terms of biodiversity, management approaches that build SOM may also be directly correlated with biodiversity gains and losses. Conversely, mismanagement can release large quantities of carbon to the atmosphere, lower soil productivity, contaminate drinking water, and cause eutrophication in aquatic ecosystems, which also leads to biodiversity declines.

The Managing Soil Carbon Working Group is addressing the two known primary knowledge gaps impeding science-based management of the world’s soils:

  • First, while there is a new estimate of how much soil carbon has been lost due to human activity, those estimates are at the global scale. The working group will now be able to pair those estimates with more site-specific data to develop robust estimates for how much soil carbon could potentially be built up in real places. Most aims at building up SOM focus on management effects. But the ability of soil to build up carbon depends largely on the physical soil properties in a given environment. The working group will focus on these soil properties to estimate hot spots of with the most potential to build up soil organic matter. They will do this for California rangelands and Midwestern row-crop agriculture under different realistic scenarios of land management.
  • Second, while the importance of soils—and SOM in particular—to human and environmental outcomes is qualitatively well established, there is no quantitative, predictive link between SOM and ecosystem services. To enable the proper valuation of soil, the group will develop estimates of the relationship between SOM and the value of soil as a capital stock input to crop and livestock production. These estimates will be used to assess the potential for targeted management strategies to increase revenues of land managers by managing for improved soil outcomes.

The work will also estimate the economic value of soil as a capital stock, allowing it to be included generally as a component of economic models and conservation decision-making models, such as InVEST.

By the end of its charter, the working group aims to provide quantified, data-based estimates of the potential specific management strategies have to build up soil carbon (reducing CO2 stocks), increase grassland biodiversity, and reduce nutrient loss from agriculture to water systems.

Inquiry Activities & Updates

Field Testing Guidelines in the Real World

To field test its outcomes and methodologies for real-world application, the working group will use scientific data analysis to create clear, management-relevant guidelines for two place-based Conservancy projects:

  • carbon sequestration and sustainable livestock production in California rangelands, and
  • crop yield and nutrient and sediment retention through the Soil Health Partnership in the U.S. Midwest.

The group’s work will also enable the synthesis and application of data and information from several separate, but related and currently ongoing soil research activities being led by members of the working group, including:

  • a global meta-analysis on the influence of SOM on crop yields;
  • an existing Nature Conservancy-Cambridge University partnership that is assessing the evidence for agricultural management to contribute to several ecosystem service outcomes (including SOM) in Mediterranean-like ecosystems such as CA;
  • the collection and analysis of new soil data from Conservancy sites around the world (including the Soil Health Partnership and California field testing sites mentioned above) to assess how management strategies are impacting SOM;
  • the identification of practices in California rangelands that have the greatest potential for improved carbon sequestration and storage, and biodiversity outcomes.

The first full working group meeting is scheduled for Winter/Spring 2017.

The Team

Managing Soil Carbon Working Group