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Dry season forage assessment across senegalese rangelands using earth observation data

Year of publication 2022

Place of publication Rome, Italy ;

Pages 15 p.

Author Adama, L.; Diouf, A.; Diedhiou, I.; Bassène, C.D.E.; Leroux, L.; Tagesson, T.; Fensholt, R.; Pierre, H.; Mottet, A.; Taugourdeau, S.; Ngom, D.; Touré, I.; Ndao, B.; Sarr, M.A.;

Publisher Frontiers Media S.A. ;

Product type Article

Synopsis (short abstract) Strengthening of feed security in the Sahel is urgently needed given the climate change and growing human population. A prerequisite to this is sustainable use of rangeland forage resources for livestock. Many studies have focused on the assessment of rangeland resources during the rainy season, while only a few have focused on the dry season which is the longest and most demanding period for livestock in Sahelian rangelands. The objective of this study is to develop remote sensing-based models for estimating dry season forage vegetation mass. To that end, 29 vegetation indices calculated from each of the MODIS-MCD43A4 (500 m), Landsat-8 (30 m), and Sentinel-2 (10 m) satellite products were used and tested against in situ data collected during three field-measurement campaigns in 2021 at eleven monitoring sites across Senegalese rangelands. Four statistical models were tested, namely, random forest, gradient boosting machines, and simple linear and multiple linear regressions. The two main vegetation mass variables modeled from remote sensing imagery were the standing herbaceous and litter dry mass (BH) and total forage dry mass (BT) with a dry mass of woody plant leaves added to BH. Overall, Sentinel-2 data provided the best performance for the assessment of BH with multiple linear regression (R2 = 0.74; RMSE = 378 kg DM/ha) using NDI5 (Normalized Difference Index5), GRCI (Green Residue Cover Index), SRI (Simple Ratio Index), TCARI (Transformed Chlorophyll Absorption in Reflectance Index), and DFI (Dead Fuel Index) indices. For BT, the best model was also obtained from Sentinel-2 data, including RVI3 (Ratio Vegetation Index3) (R2 = 0.78; RMSE = 496 kg DM/ha). Results showed the suitability of combining the red, green, blue, NIR, SWIR1, and SWIR2 bands in monitoring forage availability during the dry season. Our study revealed that the spectral richness of the optical sensor systems Sentinel-2, Landsat-8, and MODIS-MCD43A4 allowed for accurate assessments of dry-season forage mass of semi-arid rangelands. Adding to this, the high spatial and temporal resolution of Sentinel-2 satellite imagery makes this a promising data source for timely monitoring. These findings can support the monitoring of the animal feed balance in Sahelian countries and contribute to enhancing the resilience of pastoralism toward feed shortage through early warning systems.

Open Acess Article. This article is academically peer reviewed and published externally. This article is published in Frontiers in Environmental Science published 29 September 2022

Cite this content as:

Lo, A., Diouf, A.A., Diedhiou, I., Bassène, C.D.E., Leroux, L., Tagesson, T., Fensholt, R. et al. 2022. Dry season forage assessment across senegalese rangelands using earth observation data. Frontiers in Environmental Science, 10: 931299. https://doi.org/10.3389/fenvs.2022.931299


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