Carbon for soils, not soils for carbon

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Science

Background:

• Soil organic carbon (SOC) sequestration is increasingly promoted as a dual solution for climate change mitigation and food security.
• Current global strategies often overlook the complexity of SOC saturation and its impact on climate benefits.
• Observed effects of increasing SOC on crop yields are highly variable, ranging from negative to positive.

Purpose of the Study:

• To critically re-examine the purported benefits of global SOC sequestration strategies on climate change mitigation and food production.
• To assess the impact of SOC saturation on climate change mitigation estimates.
• To evaluate the consistency of yield responses to increased SOC levels.

Main Methods:

• Inclusion of SOC saturation in climate change mitigation estimations.
• Systematic review of over 21 meta-analyses on the effects of SOC on crop yields.
• Critical analysis of existing knowledge to challenge global SOC sequestration agendas.

Main Results:

• Accounting for SOC saturation reduces potential climate change mitigation by 53%-81% by 2100.
• Observed yield effects of increasing SOC are inconsistent across different studies and conditions.
• The 'win-win' outcome of SOC sequestration is only realized under specific land management practices and local contexts.

Conclusions:

• Existing knowledge does not support global agendas prioritizing SOC sequestration.
• A shift towards 'soil-smart agriculture,' adapted to local contexts and quantifying multiple soil functions, is necessary.
• SOC sequestration should be viewed as a potential co-benefit rather than a primary goal for agricultural soils.