Land Degradation States and Trends in the Northwestern Maghreb Drylands, 1998–2008
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Region
2.2. Methods
2.2.1. Background on 2dRUE
2.2.2. Assessment of Land Condition States
- Semi-arid and more humid zones, on the one hand, and arid zones, on the other, were processed separately in view of their probably different ecological responses to aridity and frequency distributions within the study area. Hyper-arid zones were excluded from the analysis.
- Scatterplot boundary functions were fitted as usual for the long- and short-term implementations. The 1st and 99th percentiles were used to delimit the boundaries. Relative mean and extreme RUE (rRUEme and rRUEex) were then computed.
- Confidence intervals (α = 0.05) were computed for the upper and lower boundary functions of RUEOBS_me. This resulted in a five-zone system in the scatterplot, which provided a basic legend for the assessment map:
- Underperforming anomaly: Vegetation below the confidence interval of minimum RUE. For example, heavily-disturbed areas.
- Baseline performance: Vegetation within the confidence interval of minimum RUE. For example, vegetation limited by factors other than rain, such as saline soils.
- Range: Vegetation between both minimum and maximum RUE confidence intervals. Target class under a variety of uses to be further processed.
- Reference performance: Vegetation within the confidence interval of maximum RUE. Typically, undisturbed natural vegetation.
- Over-performing anomaly: Vegetation above the confidence interval of maximum RUE found under rainfed conditions. For example, irrigated crops.
- The Range class was then subdivided using the relative RUE scores in both implementations. Assuming that rRUEex and rRUEme indicate productivity and biomass, respectively, their ratio was taken as a proxy for turnover. The interpretation was therefore in terms of ecological maturity following the rules below:
- Turnover below 1. Within this subpopulation, rRUEme:
- Below the 25th percentile was considered Degraded.
- From the 25th–75th percentile was considered Submature.
- Over the 75th percentile was considered Mature.
- Turnover equal to or greater than 1. Within this subpopulation, rRUEme:
- Below the 25th percentile was considered Very degraded.
- From the 25th–75th percentile was considered Productive with low biomass.
- Over the 75th percentile rRUEme was considered Productive with high biomass.
- An exception was made for the combination (a, i) above in semiarid zones, where the 25th percentile finally used corresponded to that of arid zones. This was done to improve the discrimination of grassland steppes in the plateaus, which lay in a transitional zone between those two levels of aridity.
2.2.3. Monitoring Land Condition Trends
- Increasing: Biomass accumulation over time, whatever the response to between-year variation in aridity;
- Fluctuating: Biomass fluctuates during the year with aridity, but with no significant variation in the long term;
- Static: No response detected over time, not even to changing aridity within the study period;
- Degrading: Biomass depletion over time, whatever the response to between-year variation in aridity.
2.3. Data
2.3.1. Vegetation Density Time Series
2.3.2. Climate Archive
2.3.3. Supplementary Data
2.4. Study Period and Spatial Reference
3. Results
3.1. Land State Determination
3.2. Land States and Trends in the Drylands
4. Discussion
4.1. Evaluation of the Assessment
4.2. Uncertainties and Limitations
4.3. Map Interpretation
4.4. Reporting Progress Indicators to the UNCCD
5. Conclusions
Supplementary Materials
Acknowledgments
Author Contributions
Conflicts of Interest
Abbreviations
AGTE | Ad Hoc Advisory Group of Technical Experts on Impact Indicator Refinement |
ANPP | Aboveground Net Primary Productivity |
CRS | Coordinate Reference System |
EPSG | European Petroleum Survey Group |
ETRS | European Terrestrial Reference System |
FAO | Food and Agriculture Organization of the United Nations |
GLADA | Global Assessment of Land Degradation and Improvement |
GLASOD | Global Assessment of Human-Induced Soil Degradation |
KML, KMZ | Keyhole Markup Language |
LADA | Land Degradation Assessment in Drylands |
MVC | Maximum Value Composite |
NDVI | Normalized Difference Vegetation Index |
PET | Potential Evapotranspiration |
RUE | Rain Use Efficiency |
SDG | Sustainable Development Goals |
SOC | Soil Organic Carbon |
UNCCD | United Nations Convention to Combat Desertification |
UNEP | United Nations Environment Program |
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Class | Morocco | Algeria | Tunisia | |
---|---|---|---|---|
States (χ2 = 3286.60, d.f. = 18, p < 0.0001) | Underperforming anomalies | 4.12 | −4.73 | 1.17 |
Baseline performance | 11.09 | −11.85 | 1.82 | |
Very degraded | 18.99 | −7.58 | −15.94 | |
Degraded | 2.26 | 0.71 | −4.32 | |
Productive with low biomass | −26.29 | 24.87 | 0.51 | |
Productive with high biomass | −6.93 | 4.32 | 3.48 | |
Submature | −16.70 | 4.88 | 16.69 | |
Mature | 16.68 | −16.22 | 0.35 | |
Reference performance | 31.31 | −23.91 | −9.18 | |
Over-performing anomalies | 22.52 | −17.07 | −6.79 | |
Trends (χ2 = 1096.33, d.f. = 6, p < 0.0001) | Degrading | 14.32 | −11.42 | −3.46 |
Fluctuating | −8.05 | −1.43 | 13.73 | |
Increasing | 10.92 | 8.25 | −28.07 | |
Static | −6.91 | −4.56 | 16.77 |
Degrading | Fluctuating | Increasing | Static | |
---|---|---|---|---|
Underperforming anomalies | 12.07 | 0.10 | −0.16 | −1.91 |
Baseline performance | 0.51 | −0.39 | 5.63 | −4.86 |
Very degraded | −4.07 | 19.31 | 4.64 | −15.96 |
Degraded | −4.87 | −11.66 | 24.20 | −13.27 |
Productive with low biomass | −6.09 | 1.43 | −10.95 | 9.86 |
Productive with high biomass | 2.44 | 8.85 | −20.47 | 12.16 |
Submature | 0.77 | −10.65 | 10.24 | −2.39 |
Mature | 2.36 | −6.08 | 5.99 | −1.81 |
Reference performance | 7.41 | −1.89 | −10.59 | 9.45 |
Over-performing anomalies | 13.62 | −3.24 | −5.67 | 4.90 |
Class | Arid | Semi-Arid | Dry Sub-Humid | |
---|---|---|---|---|
States (χ2 = 2377.47, d.f. = 18, p < 0.0001) | Underperforming anomalies | −3.56 | 3.91 | −1.31 |
Baseline performance | −3.70 | 2.99 | 3.15 | |
Very degraded | 3.41 | −1.66 | −7.47 | |
Degraded | 27.58 | −26.62 | −5.20 | |
Productive with low biomass | −2.54 | 5.09 | −10.57 | |
Productive with high biomass | −28.49 | 28.50 | 1.22 | |
Submature | 17.13 | −17.64 | 1.37 | |
Mature | −10.42 | 6.71 | 16.01 | |
Reference performance | 1.22 | −4.70 | 14.52 | |
Over-performing anomalies | −8.38 | 8.68 | −0.90 | |
Trends (χ2 = 2981.48, d.f. = 6, p < 0.0001) | Degrading | −6.96 | 5.87 | 4.85 |
Fluctuating | −53.75 | 52.47 | 7.71 | |
Increasing | 13.28 | −13.07 | −1.47 | |
Static | 24.04 | −23.22 | −4.47 |
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Del Barrio, G.; Sanjuan, M.E.; Hirche, A.; Yassin, M.; Ruiz, A.; Ouessar, M.; Martinez Valderrama, J.; Essifi, B.; Puigdefabregas, J. Land Degradation States and Trends in the Northwestern Maghreb Drylands, 1998–2008. Remote Sens. 2016, 8, 603. https://doi.org/10.3390/rs8070603
Del Barrio G, Sanjuan ME, Hirche A, Yassin M, Ruiz A, Ouessar M, Martinez Valderrama J, Essifi B, Puigdefabregas J. Land Degradation States and Trends in the Northwestern Maghreb Drylands, 1998–2008. Remote Sensing. 2016; 8(7):603. https://doi.org/10.3390/rs8070603
Chicago/Turabian StyleDel Barrio, Gabriel, Maria E. Sanjuan, Azziz Hirche, Mohamed Yassin, Alberto Ruiz, Mohamed Ouessar, Jaime Martinez Valderrama, Bouajila Essifi, and Juan Puigdefabregas. 2016. "Land Degradation States and Trends in the Northwestern Maghreb Drylands, 1998–2008" Remote Sensing 8, no. 7: 603. https://doi.org/10.3390/rs8070603