The enduring world forest carbon sink

Background

Forests are critical to mitigating climate change because they absorb atmospheric carbon dioxide (CO₂) and store it in biomass and soils.  In 2023, atmospheric CO₂ levels exceeded 420 ppm, intensifying the urgency to understand terrestrial carbon sinks. Forests historically lost 180 Pg of carbon through land-use change, yet they remain central to achieving global net-zero goals by 2050. While remote sensing and modeling offer insights, this study emphasizes long-term, ground-based forest inventory data as the most reliable source for assessing trends in carbon sinks across boreal, temperate, and tropical forest biomes.

Goals and Methods

This study aims to quantify the magnitude, trends, and spatial patterns of the global forest carbon sink from 1990 to 2019 and to assess biome-specific changes and drivers. Using harmonized ground-based forest inventories from more than 90% of the global forested land, supplemented by remote-sensing data, the authors estimated carbon stocks and fluxes in living biomass, necromass, soils, and harvested wood products. The analysis employed both “stock-change” and “flow” methods across biomes to calculate decadal carbon sinks, distinguishing between intact and regrowth tropical forests. Uncertainty was quantified using Monte Carlo simulations and error propagation techniques.

Conclusions and Takeaways

This research finds that the global forest carbon sink has remained remarkably stable at approximately 3.56 ± 0.37 Pg C yr⁻¹ for three decades, equivalent to nearly half of annual fossil fuel emissions. However, biome-level dynamics diverge: carbon sinks increased in temperate (+30%) and tropical regrowth (+29%) forests but declined sharply in boreal (−36%) and tropical intact forests (−31%). Deforestation emissions offset two-thirds of the gross sink, making tropical lands nearly carbon neutral. The authors highlight that sustaining this sink depends on halting deforestation, restoring degraded lands, and improving management to prevent forest aging and disturbance-related losses. Protecting existing stocks, expanding afforestation, and adopting climate-smart forestry are crucial to maintaining forests’ role in achieving global climate targets.