Soil Organic Carbon Loss and the Hidden Cost of Global Cropland Expansion
Context: Cropland expansion is often assessed through visible land conversion, crop output, and above-ground carbon loss, yet soil organic carbon is a large, slower-moving component of the Earth system. Findings: Evidence from global inventories and meta-analyses shows that converting forests, grasslands, wetlands, and savannas to cropland commonly reduces soil organic carbon stocks, with losses concentrated in the upper soil but extending deeper under some land uses. These losses represent a carbon debt, weaken soil structure, reduce water retention, and increase vulnerability to erosion and drought. The magnitude varies by climate, soil type, prior vegetation, management, and time since conversion. Implications: Accounting for cropland expansion without soil carbon costs understates climate impacts and overstates the sustainability of agricultural frontiers. Avoiding conversion of high-carbon soils, improving yields on existing cropland, and restoring degraded soils are central to land-sector mitigation and food security.
Introduction
Cropland expansion is one of the most consequential ways humans alter the surface of the Earth. It changes albedo, hydrology, biodiversity, nutrient cycles, and the exchange of carbon between land and atmosphere. Public attention often focuses on cleared forests and lost wildlife habitat, but a substantial cost lies below the surface: the loss of soil organic carbon (SOC). SOC is the carbon contained in decomposed plant and animal matter, microbial biomass, and stabilized organic compounds within soil. It is a key indicator of soil function and a major component of the terrestrial carbon pool [1].
The hidden cost of cropland expansion is that soil carbon losses can persist…
Unlock the full research paper
Full text, findings, discussion and every reference — plus every past & future paper — comes with your Grower subscription to Climate Plant Analyser.