A comprehensive framework for assessing the accuracy and uncertainty of global above-ground biomass maps

A - Papers appearing in refereed journals

Araza, A., Bruin, S. D., Herold, M., Quegan, S., Labriere, N., Rodriguez-Veiga, P., Avitabile, V., Santoro, M., Mitchard, E. T., M.Ryan, C., L.Phillips, O., Willcock, S., Verbeeck, H., Carreiras, J., Hein, L., Schelhaas, M., Pacheco-Pascagaza, A. . M., Bispo, P. D. C., Laurin, G. V., Vieilledent, G., Slik, F., Wijaya, A., Lewis, S. L., Morel, A., Liang, J., Sukhdeo, H., Schepaschenko, D., Cavlovic, J., Gilani, H. and Lucas, R. 2022. A comprehensive framework for assessing the accuracy and uncertainty of global above-ground biomass maps. Remote Sensing of Environment. 272, p. 112917. https://doi.org/10.1016/j.rse.2022.112917

AuthorsAraza, A., Bruin, S. D., Herold, M., Quegan, S., Labriere, N., Rodriguez-Veiga, P., Avitabile, V., Santoro, M., Mitchard, E. T., M.Ryan, C., L.Phillips, O., Willcock, S., Verbeeck, H., Carreiras, J., Hein, L., Schelhaas, M., Pacheco-Pascagaza, A. . M., Bispo, P. D. C., Laurin, G. V., Vieilledent, G., Slik, F., Wijaya, A., Lewis, S. L., Morel, A., Liang, J., Sukhdeo, H., Schepaschenko, D., Cavlovic, J., Gilani, H. and Lucas, R.
Abstract

Over the past decade, several global maps of above-ground biomass (AGB) have been produced, but they exhibit significant differences that reduce their value for climate and carbon cycle modelling, and also for national estimates of forest carbon stocks and their changes. The number of such maps is anticipated to increase because of new satellite missions dedicated to measuring AGB. Objective and consistent methods to estimate the accuracy and uncertainty of AGB maps are therefore urgently needed. This paper develops and demonstrates a framework aimed at achieving this. The framework provides a means to compare AGB maps with AGB estimates from a global collection of National Forest Inventories and research plots that accounts for the uncertainty of plot AGB errors. This uncertainty depends strongly on plot size, and is dominated by the combined errors from tree measurements and allometric models (inter-quartile range of their standard deviation (SD) = 30–151 Mg ha−1). Estimates of sampling errors are also important, especially in the most common case where plots are smaller than map pixels (SD = 16–44 Mg ha−1). Plot uncertainty estimates are used to calculate the minimum-variance linear unbiased estimates of the mean forest AGB when averaged to 0.1∘. These are used to assess four AGB maps: Baccini (2000), GEOCARBON (2008), GlobBiomass (2010) and CCI Biomass (2017). Map bias, estimated using the differences between the plot and 0.1∘ map averages, is modelled using random forest regression driven by variables shown to affect the map estimates. The bias model is particularly sensitive to the map estimate of AGB and tree cover, and exhibits strong regional biases. Variograms indicate that AGB map errors have map-specific spatial correlation up to a range of 50–104 km, which increases the variance of spatially aggregated AGB map estimates compared to when pixel errors are independent. After bias adjustment, total pantropical AGB and its associated SD are derived for the four map epochs. This total becomes closer to the value estimated by the Forest Resources Assessment after every epoch and shows a similar decrease. The framework is applicable to both local and global-scale analysis, and is available at https://github.com/arnanaraza/PlotToMap. Our study therefore constitutes a major step towards improved AGB map validation and improvement.

KeywordsAGB ; Carbon cycle; Mad validation; Uncertainty assessment; Remote sensing
Year of Publication2022
JournalRemote Sensing of Environment
Journal citation272, p. 112917
Digital Object Identifier (DOI)https://doi.org/10.1016/j.rse.2022.112917
Web address (URL)https://doi.org/10.1016/j.rse.2022.112917
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Natural Environment Research Council
Publisher's version
Accepted author manuscript
Supplemental file
Output statusPublished
Publication dates
Online09 Feb 2022
Publication process dates
Accepted17 Jan 2022
PublisherElsevier Science Inc
ISSN0034-4257

Permalink - https://repository.rothamsted.ac.uk/item/987yw/a-comprehensive-framework-for-assessing-the-accuracy-and-uncertainty-of-global-above-ground-biomass-maps

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