Mapping and monitoring carbon stocks with satellite observations: a comparison of methods

TLDR

Mapping and monitoring forest carbon stocks, especially in tropical regions, is critical because deforestation and degradation contribute up to 30 % of anthropogenic emissions and are now part of climate negotiations. The study reviews how satellites can measure above‑ground biomass (AGB) and surveys a range of methods developed to map AGB across diverse conditions and regions. The authors summarize remote‑sensing modalities for AGB mapping, assess their strengths and limitations, and compare traditional field‑based classification techniques with recent data‑mining approaches that directly use optical, lidar, or radar measurements. The review demonstrates that satellite‑based, direct remote‑sensing methods produce more coherent AGB maps than non‑satellite or traditional approaches, as shown in a continental Africa case study that reduces uncertainty for carbon monitoring and markets.

Abstract

Mapping and monitoring carbon stocks in forested regions of the world, particularly the tropics, has attracted a great deal of attention in recent years as deforestation and forest degradation account for up to 30% of anthropogenic carbon emissions, and are now included in climate change negotiations. We review the potential for satellites to measure carbon stocks, specifically aboveground biomass (AGB), and provide an overview of a range of approaches that have been developed and used to map AGB across a diverse set of conditions and geographic areas. We provide a summary of types of remote sensing measurements relevant to mapping AGB, and assess the relative merits and limitations of each. We then provide an overview of traditional techniques of mapping AGB based on ascribing field measurements to vegetation or land cover type classes, and describe the merits and limitations of those relative to recent data mining algorithms used in the context of an approach based on direct utilization of remote sensing measurements, whether optical or lidar reflectance, or radar backscatter. We conclude that while satellite remote sensing has often been discounted as inadequate for the task, attempts to map AGB without satellite imagery are insufficient. Moreover, the direct remote sensing approach provided more coherent maps of AGB relative to traditional approaches. We demonstrate this with a case study focused on continental Africa and discuss the work in the context of reducing uncertainty for carbon monitoring and markets.