Spatio-temporal variations in climate, primary productivity and efficiency of water and carbon use of the land cover types in Sudan and Ethiopia Muhammad Khalifa a,b, ⁎, Nadir Ahmed Elagib a , Lars Ribbe a , Karl Schneider b a Institute for Technology and Resources Management in the Tropics and Subtropics (ITT), Technische Hochschule Köln - Cologne University of Applied Sciences, Cologne 50679, Germany b Department of Geography, University of Cologne, Albertus-Magnus-Platz, D-50923 Cologne, Germany HIGHLIGHTS • Interaction between climate and vege- tation ecosystems is complex and still unclear. • Correlating climate variability and vege- tation productivity provides useful in- sights. • Spatio-temporal variations in climate, NPP, WUE and CUE using remote sens- ing data • NPP, WUE and CUE vary widely among land covers in different climate condi- tions. • This variation should be considered in policy-making for water and food security. GRAPHICAL ABSTRACT abstract article info Article history: Received 9 October 2017 Received in revised form 7 December 2017 Accepted 7 December 2017 Available online xxxx Editor: D. Barcelo The impact of climate variability on the Net Primary Productivity (NPP) of different land cover types and the re- action of NPP to drought conditions are still unclear, especially in Sub-Saharan Africa. This research utilizes pub- lic-domain data for the period 2000 through 2013 to analyze these aspects for several land cover types in Sudan and Ethiopia, as examples of data-scarce countries. Spatio-temporal variation in NPP, water use efficiency (WUE) and carbon use efficiency (CUE) for several land covers were correlated with variations in precipitation, temper- ature and drought at different time scales, i.e. 1, 3, 6 and 12 months using Standardized Precipitation Evapotrans- piration Index (SPEI) datasets. WUE and CUE were estimated as the ratios of NPP to actual evapotranspiration and NPP to Gross Primary Productivity (GPP), respectively. Results of this study revealed that NPP, WUE and CUE of the different land cover types in Ethiopia have higher magnitudes than their counterparts in Sudan. Moreover, they exhibit higher sensitivity to drought and variation in precipitation. Whereas savannah represents the most sensitive land cover to drought, croplands and permanent wetlands are the least sensitive ones. The inter-annual variation in NPP, WUE and CUE in Ethiopia is likely to be driven by a drought of time scale of three months. No statistically significant correlation was found for Sudan between the inter-annual variations in these indicators with drought at any of the time scales considered in the study. Our findings are useful from the view point of both food security for a growing population and mitigation to climate change as discussed in the present study. © 2017 Elsevier B.V. All rights reserved. Keywords: Net Primary Productivity Remote sensing Climate variability Water use efficiency Carbon use efficiency Drought Science of the Total Environment 624 (2018) 790–806 ⁎ Corresponding author at: Institute for Technology and Resources Management in the Tropics and Subtropics (ITT), Technische Hochschule Köln- Cologne University of Applied Sciences, Cologne 50679, Germany. E-mail address: mkhalifa@smail.uni-koeln.de (M. Khalifa). https://doi.org/10.1016/j.scitotenv.2017.12.090 0048-9697/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv