Soil health monitoring requires multiple indicators and continuous measurements

This post was originally published on Luke website.

A major new law on soil health in Europe is being prepared in the European Union, and scientists report that one of the proposed indicators is not fit for purpose.

Operational monitoring of soil carbon is vital to improve soil-based ecosystem services, as stated in the Paris Climate Agreement and other national commitments. As a significant proportion of Europe’s soils are unhealthy, new regulation is needed. The European Union is committed to improving soil health and is currently developing a new Soil Monitoring Law that will establish monitoring a set of different soil health indicators.

HoliSoils and Benchmarks researchers are actively contributing to the ongoing process on this European Soil Monitoring Law by testing one of the proposed indicators. A recent publication shows that the ratio of soil organic carbon to clay (SOC:Clay), proposed as part of the new law to measure soil carbon loss, is not a reliable indicator for soil health.

Single indicator and its threshold value does not adequately reflect the diversity of European soils

The joint publication by EU funded HoliSoils and Benchmarks projects assessed the feasibility of the SOC:Clay indicator by evaluating its performance using data from the pan-European 2009 LUCAS soil survey. The results were also compared with changes in soil carbon stocks reported by countries to the UNFCCC.

Based on these findings, the researchers concluded that the SOC:Clay indicator proposed by the European Commission in the Soil Monitoring Law does not adequately monitor soil carbon status. They demonstrated that the use of this single indicator and its proposed threshold value of 1:13 for all soils under different land cover, management practices and climatic conditions, cannot account for the diversity of European soils, management practices, and climatic conditions.

The results also show that the SOC:Clay indicator provides an inconsistent conclusion on the proportions of non-healthy soils identified by using the SOC:Clay indicator when compared to changes in soil carbon stocks reported by national greenhouse gas (GHG) inventories. GHG inventories estimate changes in soil carbon stocks through repeated measurements or modelling. However, the proposed indicator, which would be based on the sampling and analysis of soil samples taken at a single point in time, may have therefore temporal limitations.

Soil monitoring indicators and tools need further development

The proposal for the Soil Monitoring Law has been discussed and voted on by the EU Parliament, after which it will be subject to further trilogue negotiations which will remain the responsibility of the next Parliament after the EU elections in June. Trilogue brings together the representatives of the European Parliament, the Council of the European Union and the European Commission and aims to reach a provisional agreement on the legislative proposal.

“The sustainable production of ecosystem services relies on healthy soils. To achieve this across Europe, as outlined in the Soil Monitoring Law, various actions must be taken in different regions. In addition to the indicators to be determined at the EU level, national tools are also necessary to monitor soil status and maintain soil health that meet the needs of different actors” says Raisa Mäkipää, Research Professor at Luke, HoliSoils project coordinator.

HoliSoils and Benchmarks researchers are committed to providing scientific input to the ongoing process of developing the new Soil Monitoring Law that best supports Europe’s important promise of healthy soils.