HoliSoils finds proposed soil health indicator lacking

As MEPs discuss a major new law for soil health in Europe, HoliSoils researchers report that one of the proposed soil health indicators is not fit for purpose.

HoliSoils researchers are actively contributing to the current discussion on EU soil monitoring law Soil health – European Commission by testing one of the proposed soil health indicators.

In a pre-print of a forthcoming publication, project coordinators Raisa Mäkipää and Aleksi Lehtonen, with other consortium members and in collaboration with researchers from the Horizon Europe Benchmarks project, have found that the organic carbon-to-clay ratio, proposed as part of the new law for measuring soil carbon, is not a reliable indicator of soil health.

The operational monitoring of soil carbon is vital for improving soil-based ecosystem services, as identified in the Paris Climate Agreement and other national commitments. As substantial fractions of European soils are unhealthy, new regulation is needed. The European Union is committed to enhancing soil health, and the European Commission is currently defining a new Soil Monitoring Law, recommending the monitoring of soil carbon loss, among other soil health indicators.

The study for publication, carried out through the HoliSoils and Benchmarks projects, evaluates the feasibility of the proposed soil carbon loss indicator by assessing its performance using the EU-wide 2009 LUCAS soil survey data. The results are also compared with the soil carbon stock changes reported by countries to the climate convention (UNFCCC).

Results reveal that differences in the soil organic carbon (SOC) and clay content at European scale is in fact greater than that of the data used to develop the proposed indicator. Furthermore, the variation in SOC content was influenced not only by clay content but also by climate and land-use. Other observations included discrepancies between the soil carbon stock changes reported by the national GHG inventories and the proportions of degraded soils identified by using the soil health indicator.

These findings led the researchers to conclude that the indicator proposed by the European Commission for the Soil Monitoring Law cannot adequately monitor the loss of soil carbon. A single indicator such as SOC:Clay ratio, with one threshold value for all soils across various land covers, management practices, and climatic conditions, is unable to respond to the variety of soils, climates and uses across Europe, and is thus inappropriate for monitoring soil carbon loss.

The EU Soil Monitoring Law will next be discussed by MEPs and stakeholders in the EU Parliament on 31 January 2024: Soil Monitoring for Better Knowledge – Renew Europe (reneweuropegroup.eu).  HoliSoils researchers remain committed to continue providing scientific knowledge to inform this ongoing process for a new soil monitoring law that will best support Europe its important pledge for healthy soils. 

Read the full pre-print!

Reference

Mäkipää, Raisa and Menichetti, Lorenzo and Martínez-García, Eduardo and Törmänen, Tiina and Lehtonen, Aleksi, Is the Organic Carbon-to-Clay Ratio a Reliable Indicator of Soil Health?. Available at SSRN: https://ssrn.com/abstract=4681574 or http://dx.doi.org/10.2139/ssrn.4681574