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Estimating and Mapping Forest Carbon Sequestration in the Mau Forest Complex Using Sentinel-2 Remote Sensing and Machine Learning

Received: 8 September 2026     Accepted: 27 September 2026     Published: 23 October 2026
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Abstract

Accurate forest-carbon estimates are essential for climate mitigation, restoration planning and monitoring, reporting and verification, yet conventional field inventories are expensive and spatially discontinuous. This study evaluated whether freely available Sentinel-2 imagery combined with statistical and machine-learning models can estimate and map forest carbon across the Mau Forest Complex, Kenya. Existing geo-referenced forest inventory data comprising 3,907 measured trees were linked to seven Sentinel-2 vegetation indices: Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), Normalized Difference Moisture Index (NDMI), Normalized Burn Ratio (NBR), red-edge Chlorophyll Index (CIre) and Red-Edge Normalized Difference Vegetation Index (RENDVI). Above-ground biomass was estimated using a pan-tropical allometric equation; below-ground biomass, carbon stock and CO2 equivalent were subsequently derived using IPCC factors. Ordinary linear regression, a linear mixed-effects model, Random Forest and Extreme Gradient Boosting (XGBoost) were compared using a 70:30 training-test split, with five-fold cross-validation for machine-learning hyperparameter tuning. All vegetation indices were positively associated with above-ground biomass (p<0.001), with CIre (Pearson r=0.530), RENDVI (r=0.516) and NDMI (r=0.513) among the strongest correlates. On the independent test set, XGBoost performed best (R2=0.473, RMSE=0.424, MAE=0.327), followed by Random Forest (R2=0.468, RMSE=0.426, MAE=0.329), the mixed-effects model (R2=0.454, RMSE=0.431, MAE=0.333) and linear regression (R2=0.436, RMSE=0.438, MAE=0.340). XGBoost reduced RMSE by 3.3% relative to the linear baseline. Residual spatial autocorrelation was negligible (Moran’s I=0.059). Spatial prediction identified higher carbon densities in western and south-western portions of the Complex and lower values in more disturbed eastern blocks. The study contributes a reproducible, low-cost benchmark of linear, mixed-effects and ensemble models for spatial forest-carbon monitoring in a heterogeneous African montane forest; the modest gain from nonlinear models shows that optical indices alone limit accuracy, so future improvements will likely require structural information from radar or LiDAR.

Published in Applied and Computational Mathematics (Volume 15, Issue 5)
DOI 10.11648/j.acm.20261505.16
Page(s) 206-219
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2026. Published by Science Publishing Group

Keywords

Mau Forest Complex, Above-ground Biomass, Carbon Sequestration, Sentinel-2, Random Forest, XGBoost, Remote Sensing, REDD+

References
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  • APA Style

    Onyango, F. J., Wamwea, C., Langat, A. K. (2026). Estimating and Mapping Forest Carbon Sequestration in the Mau Forest Complex Using Sentinel-2 Remote Sensing and Machine Learning. Applied and Computational Mathematics, 15(5), 206-219. https://doi.org/10.11648/j.acm.20261505.16

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    ACS Style

    Onyango, F. J.; Wamwea, C.; Langat, A. K. Estimating and Mapping Forest Carbon Sequestration in the Mau Forest Complex Using Sentinel-2 Remote Sensing and Machine Learning. Appl. Comput. Math. 2026, 15(5), 206-219. doi: 10.11648/j.acm.20261505.16

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    AMA Style

    Onyango FJ, Wamwea C, Langat AK. Estimating and Mapping Forest Carbon Sequestration in the Mau Forest Complex Using Sentinel-2 Remote Sensing and Machine Learning. Appl Comput Math. 2026;15(5):206-219. doi: 10.11648/j.acm.20261505.16

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  • @article{10.11648/j.acm.20261505.16,
      author = {Fred Junior Onyango and Charity Wamwea and Amos Kipkorir Langat},
      title = {Estimating and Mapping Forest Carbon Sequestration in the Mau Forest Complex Using Sentinel-2 Remote Sensing and Machine Learning},
      journal = {Applied and Computational Mathematics},
      volume = {15},
      number = {5},
      pages = {206-219},
      doi = {10.11648/j.acm.20261505.16},
      url = {https://doi.org/10.11648/j.acm.20261505.16},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.acm.20261505.16},
      abstract = {Accurate forest-carbon estimates are essential for climate mitigation, restoration planning and monitoring, reporting and verification, yet conventional field inventories are expensive and spatially discontinuous. This study evaluated whether freely available Sentinel-2 imagery combined with statistical and machine-learning models can estimate and map forest carbon across the Mau Forest Complex, Kenya. Existing geo-referenced forest inventory data comprising 3,907 measured trees were linked to seven Sentinel-2 vegetation indices: Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), Normalized Difference Moisture Index (NDMI), Normalized Burn Ratio (NBR), red-edge Chlorophyll Index (CIre) and Red-Edge Normalized Difference Vegetation Index (RENDVI). Above-ground biomass was estimated using a pan-tropical allometric equation; below-ground biomass, carbon stock and CO2 equivalent were subsequently derived using IPCC factors. Ordinary linear regression, a linear mixed-effects model, Random Forest and Extreme Gradient Boosting (XGBoost) were compared using a 70:30 training-test split, with five-fold cross-validation for machine-learning hyperparameter tuning. All vegetation indices were positively associated with above-ground biomass (p2=0.473, RMSE=0.424, MAE=0.327), followed by Random Forest (R2=0.468, RMSE=0.426, MAE=0.329), the mixed-effects model (R2=0.454, RMSE=0.431, MAE=0.333) and linear regression (R2=0.436, RMSE=0.438, MAE=0.340). XGBoost reduced RMSE by 3.3% relative to the linear baseline. Residual spatial autocorrelation was negligible (Moran’s I=0.059). Spatial prediction identified higher carbon densities in western and south-western portions of the Complex and lower values in more disturbed eastern blocks. The study contributes a reproducible, low-cost benchmark of linear, mixed-effects and ensemble models for spatial forest-carbon monitoring in a heterogeneous African montane forest; the modest gain from nonlinear models shows that optical indices alone limit accuracy, so future improvements will likely require structural information from radar or LiDAR.},
     year = {2026}
    }
    

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    AU  - Fred Junior Onyango
    AU  - Charity Wamwea
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    AB  - Accurate forest-carbon estimates are essential for climate mitigation, restoration planning and monitoring, reporting and verification, yet conventional field inventories are expensive and spatially discontinuous. This study evaluated whether freely available Sentinel-2 imagery combined with statistical and machine-learning models can estimate and map forest carbon across the Mau Forest Complex, Kenya. Existing geo-referenced forest inventory data comprising 3,907 measured trees were linked to seven Sentinel-2 vegetation indices: Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), Soil-Adjusted Vegetation Index (SAVI), Normalized Difference Moisture Index (NDMI), Normalized Burn Ratio (NBR), red-edge Chlorophyll Index (CIre) and Red-Edge Normalized Difference Vegetation Index (RENDVI). Above-ground biomass was estimated using a pan-tropical allometric equation; below-ground biomass, carbon stock and CO2 equivalent were subsequently derived using IPCC factors. Ordinary linear regression, a linear mixed-effects model, Random Forest and Extreme Gradient Boosting (XGBoost) were compared using a 70:30 training-test split, with five-fold cross-validation for machine-learning hyperparameter tuning. All vegetation indices were positively associated with above-ground biomass (p2=0.473, RMSE=0.424, MAE=0.327), followed by Random Forest (R2=0.468, RMSE=0.426, MAE=0.329), the mixed-effects model (R2=0.454, RMSE=0.431, MAE=0.333) and linear regression (R2=0.436, RMSE=0.438, MAE=0.340). XGBoost reduced RMSE by 3.3% relative to the linear baseline. Residual spatial autocorrelation was negligible (Moran’s I=0.059). Spatial prediction identified higher carbon densities in western and south-western portions of the Complex and lower values in more disturbed eastern blocks. The study contributes a reproducible, low-cost benchmark of linear, mixed-effects and ensemble models for spatial forest-carbon monitoring in a heterogeneous African montane forest; the modest gain from nonlinear models shows that optical indices alone limit accuracy, so future improvements will likely require structural information from radar or LiDAR.
    VL  - 15
    IS  - 5
    ER  - 

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