1. LADA WORKSHOP 16 – 18 September 2008
GLADA-SA VERIFICATION REPORT Land Degradation and Improvement in South Africa (Bai & Dent, 2007)
LADA WORKSHOP
16 – 18 September 2008
Dirk Pretorius

2. CONTENTS
Introduction
Evaluation procedure
Results
Recommendations

3. INTRODUCTION DoA funded various land degradation assessment projects:
Evaluated the use of Landsat 5 satellite data in erosion assessment (1995)
Evaluated the use of Landsat 5 satellite data in determining the status of the natural agricultural resources (1998)
Land degradation assessment with NOAA AVHRR (1km) data in (2000)
Soil loss prediction and grazing capacity map (2005)

4. MOST RELEVANT TO GLADA
Assessing the effects of human-induced land degradation in the former homelands of northern South Africa with a 1km AVHRR NDVI time-series (Wessels et al, 2004)
This study was expanded to the whole of SA in 2005

5. ACCORDING TO DR. WESSELS
“Therefore, RUE was not a reliable indicator of degradation. The RESTREND method showed promising results at a national scale and in the Limpopo Province, where negative trends were often associated with degraded areas in communal lands. Both positive and negative residual trends can, however, result from natural ecological processes, e.g. the carryover effects of rainfall in previous years. Thus, the RESTREND method can only identify potential problem areas at a regional scale, while the cause of negative trends has to be determined by local investigations”

6. Evaluation procedure
The evaluation of the GLADA report on Land Degradation and Improvement in South Africa was based on:
Field and visual verification by the Department of Agriculture
An expert evaluation of the methodology and results by professor MC Laker
A review of the applied methodology by Dr. K Wessels

7. TOOLS USED DURING FIELD AND VISUAL EVALUATION

8. RESULTS – DOA EVALUATION (MOST ISSUES ALSO HIGHLIGHTED BY PROF
RESULTS – DOA EVALUATION (MOST ISSUES ALSO HIGHLIGHTED BY PROF. MC LAKER)
It is by no means a comprehensive verification of the spatial data produced in the report although dedicated field observations were conducted to support some of the expert observations.
GLADA results were extracted for point as well as an 8km buffered area.
The zonal statistics analysis (165 sites analysed) indicated a 33% and 48% correlation between the observation and negative trend GLADA data for the point and 8km buffered areas (majority values) respectively.

9. MAJOR DISCREPANCIES Plantations in most parts of the country
Conservation areas – focus on the Kruger
National Park
Cultivated areas
Degraded arid areas
Kalahari Dune Veld

10. EXAMPLES - PLANTATIONS

11. EXAMPLES – CONSERVATION AREAS

12. EXAMPLES – CULTIVATION

13. EXAMPLES – DEGRADED AREAS

14. EXAMPLES – KALAHARI DUNE VELD

15. COMMENTS BY DR. WESSELS
The use of global remote sensing dataset to monitor land degradation is definitely a step in the right direction and a vast improvement on previous efforts which were only based on expert opinions.
On the other hand, the outputs of the RESTREND method have also not yet been sufficiently validated and thus there is no guarantee that it will provide more reliable results.
As the RUE trend products stand now they should not be used to drive any policies or interventions. The products should be subjected to rigorous validation efforts involving high resolution data and field work.

16. RECOMMENDATIONS BY DOA
The GLADA land degradation and improvement mapping methodology used to produce the negative and positive trends maps for South Africa needs serious rethinking.
It seems to be a fact that a method to map and monitor degradation at a global level at an acceptable level of accuracy has yet to be developed.
It is also recommended that a multidisciplinary approach be followed to produce a global land degradation and improvement map. If this approach is not possible the global assessment should again be based on expert opinions, as the case with the national assessments.

17. FINAL STATEMENT
Comments and recommendations in this report/presentation must be viewed in a positive light. The commitment from ISRIC’s side on the assessment must not be underestimated. It is however also the commitment of DoA and others in South Africa to assist with the refinement of a global methodology to map/monitor degradation and improvement.