Mexico’s Soil Organic Carbon Sequestration Crisis: A 2070 Tipping Point

The Failure of Static Soil Organic Carbon Sequestration Models

Mexico faces a hard deadline: 2070. That is the year agricultural lands flip from carbon sinks to carbon sources under fossil-fuel-intensive trajectories. Soil organic carbon sequestration is a primary lever for terrestrial climate mitigation, yet existing projections often fail. They rely on static assumptions. They ignore the friction between economic development and climatic forcing. This limitation is severe in Mexico, where rapid agrarian shifts threaten to destabilise historic storage. The current baseline mean stock sits at 2.96 kg C/m², but this figure is precarious. Without accounting for the velocity of socioeconomic change, policymakers are flying blind.

Methodological Rigour

To correct this data gap, researchers coupled a calibrated Random Forest model (R2 = 0.45) with downscaled climate data. They did not look at a single snapshot. They projected spatiotemporal dynamics from 2021 through 2100 across Mexico's diverse ecoregions. The team integrated these projections with four distinct Shared Socioeconomic Pathways (SSPs). This approach moves beyond simple climate modelling. It captures the complex interaction between rainfall, temperature, and human land-use decisions. It quantifies how economic pressure forces land degradation.

Mechanism: The 63% Degradation Threshold

The data reveals a stark bifurcation. Under sustainable or intermediate pathways (SSP126, SSP245, SSP370), national stocks stabilise. They may even see a marginal gain of approximately 2%. Resilience is possible. However, the fossil-fuelled SSP585 scenario is destructive. It drives a continuous decline below baseline levels. The specific mechanism of failure is cropland degradation.

Currently, 36.7% of cropland is degrading. Under SSP585, this figure escalates to 63.2%. The system reaches a saturation point. After 2070, the agricultural sector ceases to function as a net sink. It begins emitting more carbon than it stores. The soil structure collapses under the weight of intensive use and climatic stress.

Strategic Implications: Policy as the Control Variable

This is a quantitative warning for global carbon markets. If Mexico’s soil becomes a net source, offsets purchased in this region lose their validity. The findings suggest that future stability is not merely a climatic outcome. It is determined by policy. Land-use choices are the dominant variable. The difference between a 2% gain and a collapse into a carbon source lies entirely in the socioeconomic pathway chosen today.

Immediate intervention is required in threatened agricultural zones. Policymakers must prioritise soil health over short-term yield maximisation in these specific regions. If they fail, the very ground intended to solve the climate crisis will accelerate it. Data-driven preservation is no longer optional; it is the only barrier against the 2070 inversion.