Know more

Article published in August 2019 in the Global Change Biology journal.

Summary

There is growing international interest in better managing soils to increase soil organic carbon content to contribute to climate change mitigation, to enhance resilience to climate change and to underpin food security, through initiatives such as international “4p1000″ initiative and the FAO's Global assessment of soil organic carbon sequestration potential (GSOCseq) programme. Since soil organic carbon content of soils cannot be easily measured, a key barrier to implementing programmes to increase soil organic carbon at large scale, is the need for credible and reliable measurement/monitoring, reporting and verification (MRV) platforms, both for national reporting and for emissions trading. Without such platforms, investments could be considered risky.

"In this paper, we review methods and challenges of measuring SOC change directly in soils, before examining some recent novel developments that show promise for quantifying SOC."

We describe how repeat soil surveys are used to estimate changes in SOC over time, and how long‐term experiments and space‐for‐time‐substitution sites can serve as sources of knowledge and can be used to test models, and as potential benchmark sites in global frameworks to estimate SOC change. We briefly consider models that can be used to simulate and project change in SOC and examine the MRV platforms for soil organic carbon change already in use in various countries/regions. In the final section, we bring together the various components described in this review, to describe a new vision for a global framework for MRV of soil organic carbon change, to support national and international initiatives seeking to effect change in the way we manage our soils.

PROPOSED GLOBAL SOIL MRV PLATFORM

The article proposes methods to measure and monitoring carbon, models to simulate SOC changes, experimental platforms and defining data needed to test those models.

They concretely propose, as shown in Figure 3, to use long-term field experiments to measure SOC changes and short-term field experiments to test novel models, data collected from those fields can, therefore, be used to establish models of SOC changes. The use of spatial data of soil characteristics can be used to simulate SOC changes and GHG emissions as well and thereby delivering a specific methodology to report emissions.
Activity data self-reported by farmers and land managers is necessary for simulations, complemented by remote sensing data to show bare fallow, cover crop or residue retention of fields could be used to ground‐truth SOC changes estimated by the Tier 2 method or Tier 3 model projections over time.
Finally, a spatial soil re-sampling survey grid is needed to provide independent estimates of large scale SOC change.

Basic methodological requirements and recommendations

In order to support scientific and policy decisions, authors provide a list of basic methodological requirements and recommendations for ‘good SOC‐monitoring and MRV practice’. They recommend:

1. The provision of long‐term continuity and consistency under changing boundary conditions, such as biophysical site conditions, climate change, methodologies, socio‐economic setting, and policy context
2. Adoption of a scientifically and politically (e.g. for GRA, UNFCCC, UNNCCD) appropriate spatial and temporal resolution for the measurements
3. Ensuring continuous quality assurance at all stages of the measurement and monitoring process
4. Measurement/observation and documentation of all potential drivers of SOC and GHG change
5. Soil monitoring network‐collated, georeferenced samples archived and the associated (harmonized) data made accessible through distributed databases to enhance the value of the collated data for multiple uses.

An example of a soil monitoring network and open‐access database for a cross‐method validation programme would be the Open Collaborative Platfom developed in the frame of CIRCASA project, as cited in this article. 

See the full article: https://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.14815#.XWoInMNaqao.twitter