Long-Term Spatio-Temporal Assessment of Land Use Dynamics and Ecosystem Service Values in Wadi Jazan, Saudi Arabia, Using GIS and Remote Sensing

Technical Summary: Long-Term Spatio-Temporal Assessment of Land Use Dynamics and Ecosystem Service Values in Wadi Jazan, Saudi Arabia

Problem Statement
Coastal and fluvial ecosystems in semi-arid regions face significant pressures from rapid urbanization, agricultural intensification, and climate variability, often leading to ecological degradation. While ecosystem service valuation (ESV) is a recognized tool for decision-making, existing literature predominantly focuses on humid or temperate regions, leaving semi-arid coastal–fluvial systems like Wadi Jazan underrepresented. Furthermore, many studies rely on static or short-term assessments, failing to capture long-term spatio-temporal dynamics, cumulative anthropogenic impacts, and the spatial heterogeneity of ecosystem service degradation. This study addresses these gaps by investigating the land use/land cover (LULC) changes and associated ESV dynamics in Wadi Jazan, southwest Saudi Arabia, over a 22-year period (2000–2022).

Methodology
The study employed an integrated approach using Geographic Information Systems (GIS), Remote Sensing (RS), and a value transfer approach to assess LULC dynamics and ESV.

• Data Sources: Multi-temporal Landsat imagery (Landsat-5 TM for 2000, Landsat-7 ETM+ for 2011, and Landsat-8 OLI/TIRS for 2022) was utilized. All images were acquired in July to capture peak vegetation conditions and were geometrically and atmospherically corrected. Topographic data were derived from a 30m SRTM Digital Elevation Model (DEM).
• LULC Classification: A supervised classification using the Maximum Likelihood classifier was applied to generate maps for six LULC classes: Water Bodies, Cultivated Areas, Natural Vegetation, Built-up Areas, Bare Land, and Rocky Outcrops. Classification accuracy was validated using high-resolution imagery and field data, achieving overall accuracies of 81% (2000), 82% (2011), and 87% (2022).
• Change Detection: Post-classification comparison techniques were used to quantify transitions between LULC classes across the two sub-periods (2000–2011 and 2011–2022) and the full study duration.
• ESV Assessment: Ecosystem Service Values were estimated using a value transfer approach, applying standardized monetary coefficients (USD/ha/year) derived from global studies (e.g., Costanza et al.) and regional adjustments. The total ESV was calculated by multiplying the area of each LULC class by its corresponding coefficient. Sensitivity analyses (±25% and ±50% adjustments) were conducted to assess the robustness of the valuation results.

Key Results

• LULC Dynamics: The study identified two distinct phases of landscape transformation.
  • 2000–2011: Characterized by agricultural expansion. Cultivated land increased from 3.31% to 10.09% of the total area, primarily converting Bare Land and Natural Vegetation.
  • 2011–2022: Marked by rapid urbanization. Built-up areas surged nearly ninefold, increasing from 0.61% (1,570 ha) in 2000 to 5.56% (14,269 ha) in 2022. This expansion occurred largely at the expense of cultivated land (which declined from 10.09% to 3.54%) and Bare Land.
  • Vegetation Trends: Natural vegetation showed a steady increase, rising from 10.67% (27,394 ha) in 2000 to 19.29% (49,538 ha) in 2022, with significant recovery observed in upland areas. Conversely, Bare Land declined continuously from 15.08% to 5.24%.
• Ecosystem Service Value (ESV):
  • Total ESV increased from 170.1 million USD/year in 2000 to 348.89 million USD/year in 2022 (a ~105% increase).
  • However, this aggregate gain masked significant structural redistribution. The value associated with Natural Vegetation grew by 80.8%, and Built-up Areas increased by 809.7% (driven by the assigned economic coefficients for urban areas).
  • Cultivated Areas saw a net increase of only 6.7% over the full period, with a sharp decline of 65% in ESV between 2011 and 2022.
  • Water bodies, despite having the highest per-unit ESV coefficient (12,512 USD/ha/year), contributed minimally to the total system value due to their small spatial extent (<0.2%).
• Spatial Inequality and Degradation: Spatial analysis revealed that while total ESV increased, degradation hotspots are concentrated in coastal plains and downstream wadi sections. These areas experienced the conversion of productive agricultural land and natural vegetation into built-up areas, leading to a loss of regulating services (flood mitigation, soil conservation) and increased ecological vulnerability.

Key Contributions

• Long-Term Spatio-Temporal Analysis: The study provides one of the first long-term (22-year), spatially explicit assessments of ecosystem service dynamics in a semi-arid coastal–fluvial watershed, moving beyond static snapshots to capture decadal shifts.
• Identification of Trade-offs: It quantifies the trade-offs between development and ecological resilience, demonstrating that aggregate ESV gains can obscure localized ecological degradation, particularly in high-pressure coastal zones.
• Methodological Application: The research successfully applies a value transfer approach in a data-scarce semi-arid environment, highlighting the utility of GIS and RS in identifying degradation hotspots and informing land-use planning.
• Policy Relevance: The findings link specific land-use transitions (e.g., agricultural-to-urban conversion) to specific ecosystem service losses, offering evidence-based insights for sustainable land management under Saudi Vision 2030.

Significance and Claims
The paper claims that the observed increase in total ESV in Wadi Jazan reflects a redistribution of service values rather than a uniform improvement in ecological condition. The study emphasizes that the rapid urbanization phase (2011–2022) has led to a structural shift where economic and cultural services (associated with built-up areas) increasingly dominate at the expense of regulating and provisioning services.

The authors assert that without spatially explicit assessment, aggregate metrics can mask critical ecological trade-offs. The concentration of degradation in socio-economically critical coastal–fluvial zones highlights growing spatial inequality in ecosystem service provision. The study concludes that sustainable management in such semi-arid environments requires watershed-scale, ecosystem-based planning that balances economic growth with the protection of regulating functions (e.g., flood mitigation, groundwater recharge) and the restoration of degraded ecological corridors. The findings underscore the necessity of integrating spatial heterogeneity and ecosystem service trade-offs into land-use planning to ensure long-term regional resilience against anthropogenic and climatic pressures.