Can SOC lost during initial forest-to-agriculture transitions be replenished within timeframes required for effective climate mitigation (typically decades)?

Soil organic carbon (SOC) dynamics are driven by a complex matrix of factors, including local climate (e.g., temperature, precipitation), soil properties (e.g., mineralogy, clay content, cation-exchange capacity, pH), and land use (e.g., forests, grassland, arable agriculture) and its history. Each parcel of land carries a unique signature within this matrix, resulting in distinct SOC dynamics and varied responses to land-use changes and future climate scenarios.

European political and environmental strategies increasingly emphasize (re) afforestation as a key measure for climate change mitigation. This represents a full-circle transformation for European landscapes, many of which were historically deforested to accommodate grazing and agriculture. With rising reforestation rates, these landscapes are gradually returning to their forested states. However, with this, a critical ecological question arises: can SOC lost during initial forest-to-agriculture transitions be replenished within timeframes required for effective climate mitigation (typically decades)?

This study addresses this question by focusing on irrecoverable carbon stocks—SOC fractions lost during land-use transitions that cannot be restored quickly enough to meet climate targets. Using the terrestrial biosphere model T&C, which incorporates a microbially explicit soil biogeochemistry module to simulate carbon (C), nitrogen (N), and phosphorus (P) dynamics, we investigate SOC recovery potential and how this varies with land management.

Our proof-of-concept approach here presented involves a) validating the T&C model across multiple European sites undergoing forest-to-agriculture and agriculture-to-forest transitions and b) simulating SOC dynamics for a representative European grid cell experiencing these transitions under distinct Shared Socioeconomic Pathway (SSP) climate scenarios.

Such work is imperative to gain critical insights into the persistence of irrecoverable carbon stocks and the feasibility of SOC recovery through European (re)afforestation efforts.