1. Land degradation & change detection of biophysical products using multi temporal SPOT NDVI image data : a case in Blue Nile river basin, Ethiopia Taye Gidyelew International Livestock Research Institute (ILRI)

2. Introduction Land degradation is a process of progressive deterioration of biological and physical resources of the land It is a cause of low agricultural productivity for Sub– Saharan Africa in general and Ethiopia in Particular. Biophysical products such as NDVI,NPP and biomass indirectly determines land degradation

3. Intro… Remote sensing is the best method for obtaining such data Recently large volume of high quality global remotely sensed data available – SPOT – MODIS – MERIS – AVRIS/NOAA

4. Objective of the study To identify the trend of NDVI to monitor land degradation through analysis of multi temporal and multi spectral SPOT-Vegetation imageries and To determine the amount of Net Primary Product (NPP) and fraction of Absorbed Photosynthetically Active Radiation (fAPAR) in Blue Nile river basin.

5. Methodology - study site

6. Methodology

7. Algorithms to derive biophysical products Normalized Difference vegetation Index (NDVI) fAPAR = a + b *NDVI fAPAR= -0.025+1.25*NDVI Fraction of Absorbed Photosynthetically Active Radiation (fAPAR)

8. Algorithms…… Net Primary Productivity (NPP)

9. Results and discussion The biophysical products are derived from the SPOT vegetation for different LU types which are: – Dabus Valley park – Farm land – Forest area – Grass land and – Towns

11. Dabus Valley Park_ NDVI

12. Farm land_ NDVI

13. Forest area_NDVI

14. Grassland_NDVI

15. Town-NDVI

16. NDVI for all land use types The NDVI for town is appeared at the bottom of all curves followed by that of grass land and forest at the top of all

17. Overall monthly NDVI for all Land use types Time NDVINDVI

18. Summary of fAPAR and NPP Land UseMean NDVIfAPARNPPRemark Dabus0.42450.50565.98 Farm land0.39360.46704.64 Forest0.47020.56276.36Highest Grass land0.39090.46364.61 Town0.38680.45854.42Least

20. Conclusion and Recommendation The NDVI trend and the derived parameters during the seven periods time showed a declining trend. Forest area over the study area showed higher value for all the biophysical products and a minimum value is recorded in towns. Combination of Rain Use Efficiency with NDVI trends will be a good parameter to monitor the status of vegetation cover and good indicator for land degradation. Field data has to be included for validation and calibration of biophysical products for different land use types

21. Thank you ! Comments, suggestions and questions are most welcome!

23. Land cover Land use 15 years ago