Makhambetov et al. (2026) Assessment of the Spatial Structure and Condition of Urban Green Infrastructure in Aktau (Kazakhstan) Under Arid Climate Conditions Using NDVI and SAVI

Identification

• Journal: Land
• Year: 2026
• Date: 2026-03-26
• Authors: Murat Makhambetov, Aigul Sergeyeva, G Nurgaliyeva, Altynbek Khamit, A.A. Sayanov, Raushan Duisekenova
• DOI: 10.3390/land15040536

Research Groups

• Department of Ecology, K. Zhubanov Aktobe Regional University, Aktobe, Kazakhstan
• Department of Ecology, Saken Seifullin Kazakh Agrotechnical Research University, Astana, Kazakhstan
• Department of Physical and Economical Geography, L.N. Gumilyov Eurasian National University, Astana, Kazakhstan
• Department of Geography and Tourism, H. Dosmukhamedov Atyrau University, Atyrau, Kazakhstan
• Department of Rational Environmental Management, Faculty of Geography, Lomonosov Moscow State University, Moscow, Russia
• Department of Ecology and Life Safety, Caspian University of Technology and Engineering Named After Sh. Yessenov (Yessenov University), Aktau, Kazakhstan

Short Summary

This study assesses the spatial structure and condition of urban green infrastructure in Aktau, Kazakhstan, under arid climate conditions from 2015 to 2025 using satellite imagery and inventory data. It found a moderate overall increase in vegetation but with persistent spatial fragmentation and center-periphery asymmetry, emphasizing the critical role of irrigation and targeted greening strategies.

Objective

• To develop and test an integrated remote sensing–based analytical framework for assessing the condition, spatial structure, and temporal dynamics of urban green infrastructure in Aktau under arid climate conditions.
• To identify spatial patterns and the degree of fragmentation of green infrastructure.
• To analyze temporal changes in vegetation indices over a ten-year period.
• To assess intra-urban disparities in greening levels across functional zones.
• To demonstrate the potential of Normalized Difference Vegetation Index (NDVI) and Soil-Adjusted Vegetation Index (SAVI) monitoring as decision-support tools for sustainable urban planning in arid regions.

Study Configuration

• Spatial Scale: The city of Aktau, Kazakhstan (43.65° N, 51.17° E), including intra-urban functional zones (residential, industrial, recreational, central, coastal) and microdistricts.
• Temporal Scale: 2015–2025 (10-year period), with satellite observations from June 2015 and June 2025. Inventory data from 2023. Seasonal analysis for the summer vegetation period (June–August).

Methodology and Data

• Models used:
  • Normalized Difference Vegetation Index (NDVI)
  • Soil-Adjusted Vegetation Index (SAVI)
  • Zonal Statistics (ArcGIS 10.8)
  • Supervised classification using the Maximum Likelihood algorithm
  • Green Planting Density (GPD)
  • Structural Composition of Greenery (SCG)
  • Protective Green Infrastructure (PGI)
• Data sources:
  • Sentinel-2 MSI satellite imagery (Level-2A products, 10 m and 20 m spatial resolution)
  • National Land Cadastre of the Republic of Kazakhstan (vector layers)
  • Master Plan of Aktau (functional zoning materials, microdistrict boundaries)
  • 2023 dendrological inventory of Aktau (80 green infrastructure units, 1777.56 hectares)
  • Field surveys (October 2025)
  • Atlas of the Republic of Kazakhstan

Main Results

• The overall mean NDVI values for Aktau increased moderately from 0.21 in 2015 to 0.28 in 2025.
• The most significant increases in vegetation density were observed in central and coastal districts (ΔNDVI = +0.12; ΔSAVI = +0.21), reaching NDVI values of 0.45–0.55 and SAVI values of 0.49–0.60 by 2025.
• Industrial and newly developed zones showed limited changes (ΔNDVI = +0.03; ΔSAVI = +0.03) and maintained consistently low index values (NDVI 0.20–0.30, SAVI 0.18–0.29).
• The spatial configuration of urban green infrastructure remains fragmented, characterized by a persistent center–periphery asymmetry in greening levels.
• A total of 138,681 tree and shrub specimens were recorded across 80 green infrastructure units covering 1777.56 hectares.
• Deciduous tree species dominate the urban green infrastructure (74.1%), with Ulmus pumila, Populus alba, and Elaeagnus angustifolia being the most widespread taxa.
• Linear protective green elements, primarily hedgerows, total over 47,337.7 linear meters, indicating a focus on protective and buffering functions.
• Green Planting Density (GPD) varied significantly across microdistricts, ranging from 50.48 to 1463.51 plants per hectare, confirming high intra-urban differentiation.
• A positive relationship was observed between satellite-derived NDVI values and inventory-based GPD indicators at the microdistrict level.

Contributions

• Developed and applied an integrated analytical framework combining Sentinel-2 satellite-derived vegetation indices (NDVI and SAVI) with inventory-based indicators (Green Planting Density, Structural Composition of Greenery, and Protective Green Infrastructure) for a comprehensive assessment.
• Provided a detailed spatial-temporal assessment of urban green infrastructure in Aktau, Kazakhstan, an arid coastal city, addressing a research gap in less-studied arid urban environments.
• Systematically compared the sensitivity of NDVI and SAVI under arid conditions, demonstrating SAVI's robustness in areas with significant bare soil background.
• Quantified the spatial fragmentation and intra-urban disparities in greening levels, linking them to functional zones and highlighting issues of environmental inequality.
• Offered practical implications and decision-support tools for sustainable urban planning and adaptive green infrastructure management in arid and semi-arid cities facing water scarcity and climatic stress.

Funding

• Committee of Science of the Ministry of Science and Higher Education of the Republic of Kazakhstan, project IRN AP27511521: “Geoecological assessment of the state of green spaces and soil quality of the urban environment of the cities of Aktau and Atyrau using GIS technology”.

Citation

@article{Makhambetov2026Assessment,
  author = {Makhambetov, Murat and Sergeyeva, Aigul and Nurgaliyeva, G and Khamit, Altynbek and Sayanov, A.A. and Duisekenova, Raushan},
  title = {Assessment of the Spatial Structure and Condition of Urban Green Infrastructure in Aktau (Kazakhstan) Under Arid Climate Conditions Using NDVI and SAVI},
  journal = {Land},
  year = {2026},
  doi = {10.3390/land15040536},
  url = {https://doi.org/10.3390/land15040536}
}