Past decade above-ground biomass change comparisons from four multi-temporal global maps

Arnan Araza*, Martin Herold, Sytze De Bruin, Philippe Ciais, David A. Gibbs, Nancy Harris, Maurizio Santoro, Jean-Pierre Wigneron, Hui Yang, Natalia Málaga, Karimon Nesha, Pedro Rodriguez-Veiga, Olga Brovkina, Hugh C.A. Brown, Milen Chanev, Zlatomir Dimitrov, Lachezar Filchev, Jonas Fridman, Mariano García, Alexander GikovLeen Govaere, Petar Dimitrov, Fardin Moradi, Adriane Esquivel Muelbert, Jan Novotný, Thomas A.M. Pugh, Mart-Jan Schelhaas, Dmitry Schepaschenko, Krzysztof Stereńczak, Lars Hein

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

5 Citations (Scopus)

Abstract

Above-ground biomass (AGB) is considered an essential climate variable that underpins our knowledge and information about the role of forests in mitigating climate change. The availability of satellite-based AGB and AGB change (AGB) products has increased in recent years. Here we assessed the past decade net AGB derived from four recent global multi-date AGB maps: ESA-CCI maps, WRI-Flux model, JPL time series, and SMOS-LVOD time series. Our assessments explore and use different reference data sources with biomass re-measurements within the past decade. The reference data comprise National Forest Inventory (NFI) plot data, local AGB maps from airborne LiDAR, and selected Forest Resource Assessment country data from countries with well-developed monitoring capacities. Map to reference data comparisons were performed at levels ranging from 100 m to 25 km spatial scale. The comparisons revealed that LiDAR data compared most reasonably with the maps, while the comparisons using NFI only showed some agreements at aggregation levels 10 km. Regardless of the aggregation level, AGB losses and gains according to the map comparisons were consistently smaller than the reference data. Map-map comparisons at 25 km highlighted that the maps consistently captured AGB losses in known deforestation hotspots. The comparisons also identified several carbon sink regions consistently detected by all maps. However, disagreement between maps is still large in key forest regions such as the Amazon basin. The overall AGB map cross-correlation between maps varied in the range 0.11–0.29 (r). Reported AGB magnitudes were largest in the high-resolution datasets including the CCI map differencing (stock change) and Flux model (gain-loss) methods, while they were smallest according to the coarser-resolution LVOD and JPL time series products, especially for AGB gains. Our results suggest that AGB assessed from current maps can be biased and any use of the estimates should take that into account. Currently, AGB reference data are sparse especially in the tropics but that deficit can be alleviated by upcoming LiDAR data networks in the context of Supersites and GEO-Trees.
Original languageEnglish
Article number103274
Number of pages12
JournalInternational Journal of applied Earth Observation and Geoinformation
Volume118
DOIs
Publication statusPublished - Apr 2023

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